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Title: Mechanics of the Household - A Course of Study Devoted to Domestic Machinery and Household Mechanical Appliances
Author: Keene, E. S. (Edward Spencer)
Language: English
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A Course of Study Devoted to Domestic Machinery and
Household Mechanical Appliances


Dean of Mechanic Arts
North Dakota Agricultural College


Mcgraw-Hill Book Company, Inc.
239 West 39th Street. New York

London: Hill Publishing Co., Ltd.
6 & 8 Bouverie St., E. C.

Copyright, 1918, by the
Mcgraw-Hill Book Company, Inc.


This book is intended to be a presentation of the physical principles
and mechanism employed in the equipment that has been developed for
domestic convenience. Its aim is to provide information relative to
the general practice of domestic engineering. The scope of the work is
such as to present: first, the use of household mechanical appliances;
second, the principles involved and the mechanism employed. It is not
exhaustive, neither does it touch many of the secondary topics that
might be discussed in connection with the various subjects. It does,
however, describe at least one representative piece of each type of
household apparatus that is used in good practice.

The mechanism used in the equipment of a modern dwelling is worthy of
greater attention, as a course of study, than it has been heretofore
accorded. The fact that any house, rural or urban, may be provided with
all domestic conveniences included in: furnace heating, mechanical
temperature regulation, lighting facilities, water supply, sewage
disposal and other appliances, indicates the general use of domestic
machinery in great variety. To comprehend the application and
adaptability of this mechanism requires a knowledge of its general plan
of construction and principles of operation.

Heating systems in great variety utilize steam, hot water, or hot air
as the vehicle of transfer of heat from the furnace, throughout the
house. Each of these is made in the form of special heating plants that
may be adapted, in some special advantage to the various conditions of
use. A knowledge of their working principles and general mechanical
arrangement furnishes a fund of information that is of every day

The systems available for household water distribution take advantage
of natural laws, which aided by suitable mechanical devices and
conveniently arranged systems of pipes, provide water-supply plants to
satisfy any condition of service. They may be of simple form, to suit
a cottage, or elaborated to the requirements of large residences and
made entirely automatic in action. In each, the apparatus consists
of parts that perform definite functions. The parts may be obtained
from different makers and assembled as a working unit or the plant
may be purchased complete as some special system of water supply. An
acquaintance with domestic water supply apparatus may be of service in
every condition of life.

The type of illumination for a house or a group of buildings, may be
selected from a variety of lighting systems. In rural homes, choice may
be made between oil gas, gasolene, acetylene and electricity, each of
which is used in a number of successful plants that differ only in the
mechanism employed.

Any building arranged with toilet, kitchen and laundry conveniences
must be provided with some form of sewage disposal. Private disposal
plants are made to meet many conditions of service. The mechanical
construction and principles of operation are not difficult to
comprehend and their adaptation to a given service is only an
intelligent conception of the possible conditions of disposal,
dependent on the natural surroundings.

There are few communities where household equipment cannot be found to
illustrate each of the subjects discussed. Most modern school houses
are equipped for automatic control of temperature, ventilation and
humidity. They are further provided with systems of gas, water and
electric distribution and arrangements for sewage disposal. These
facilities furnish demonstration apparatus that are also examples of
their application. Additional examples of the various forms of plumbing
and pipe fittings, valves, traps and water fixtures may be found in the
shop of dealers in plumbers and steam-fitters supplies.

Attention is called to the value of observing houses in process of
construction and the means employed for the placement of the pipes for
the sewer, gas, water, electric conduits, etc. These are generally
located by direction of the specifications provided by the architect
but observation of their installation is necessary for a comprehension
of actual working conditions. It is suggested that the work be made
that of, first, acquiring an idea of established practice, and second,
that of investigating the examples of its application.


  PREFACE                                                            v



  THE STEAM HEATING PLANT                                            1

  Heat of Vaporization--Steam Temperature--Gage Pressure--Absolute
  Pressure--Two-pipe System--Separate-return System--Overhead
  or Drop System--Water-filled Radiators--Air Vents--Automatic
  Air Vents--Steam Radiator Valves--The House-heating Steam
  Boiler--Boiler Trimmings--The Water Column--The Steam Gage--The
  Safety Valve--The Draft Regulator--Rule for Proportioning
  Radiators--Proportioning the Size of Mains--Forms of
  Radiators--Radiator Finishings--Pipe Coverings--Vapor-system


  THE HOT-WATER HEATING PLANT                                       37

  The Low-pressure Hot-water System--The High-pressure Hot-water
  System--Heating-plant Design--Overhead System of Hot-water
  Heating--Expansion Tanks--Radiator Connection--Hot-water
  Radiators--Hot-water Radiator Valves--Air Vents--Automatic
  Hot-water Air Vents.


  THE HOT-AIR FURNACE                                               51

  Construction--Furnace-gas Leaks--Location of the
  Furnace--Flues--Combination Hot-air and Hot-water Heater.


  TEMPERATURE REGULATION                                            59

  Hand Regulation--Damper Regulator for Steam Boiler--Damper
  Regulators for Hot-water Furnaces--The Thermostat Motor--Combined
  Thermostat and Damper Regulator--Thermostat-motor Connections.


  MANAGEMENT OF HEATING PLANTS                                      70

  General Advice--The Economy of Good Draft--General Firing
  Rules--Weather and Time of Day--Night Firing--First-day
  Firing--Other Day Firing--Economy and Fuels--For Burning Soft
  Coal--For Burning Coke--Other Rules for Water Boilers--Air-vent
  Valves on Radiators--The Air Valves--End of the Season--The Right
  Chimney Flue--“Smokey” Chimneys.


  PLUMBING                                                          82

  Water Supply--Water Cocks--Bibb-cocks--Self-closing
  Bibbs--Lever-handle Bibbs--Fuller Cocks--Wash-tray Bibbs--Basin
  Cocks--Pantry Cocks--Sill Cocks--Valves--Kitchen and
  Laundry Fixtures--The Bathroom--Bath Tubs--Wash Stands and
  Lavatories--Traps--Back-venting--Soil Pipe--Water Closets--Washout
  Closets--Washdown Closets--Siphon-jet Closet--Flush Tanks--Low-down
  Flush Tank--Opening Stopped Pipes--Sewer Gas--Range Boilers--The
  Water-back--Excessive Pressure--Blow-off Cock--Location of Range
  Boiler--Double Heater Connections--Horizontal Range Boilers--Tank
  Heaters--Overheater Water--Furnace Hot-water Heaters--Instantaneous


  WATER SUPPLY                                                     125

  Water Analysis--Pokegama Water--River Water--Artesian
  Water--Medical Water--Organic Matter--Ammonia--Hardness
  in Water--Iron in Water--Water Softening With Hydrated
  Silicates--Chlorine--Polluted Water--Pollution of Wells--Safe
  Distance in the Location of Wells--Surface Pollution of
  Wells--Water Table--The Divining Rod--Selection of a Type of
  Well--Flowing Wells--Construction of Wells--Dug Wells--Open
  Wells--The Ideal Well--Coverings of Concrete--Artesian
  Wells--Driven Wells--Bored Wells--Cleaning Wells--Gases in
  Wells--Peculiarities of Wells--Breathing Well--Freezing
  Wells--Pumps--The Lift Pump--The Force Pump--Tank Pump--Well
  Pumps--Wooden Pump--Pumps for Driven Wells--Deep-well
  Pumps--Tubular Well Cylinders--Chain Pumps--Rain Water
  Cisterns--Filters--The Hydraulic Ram--Single-acting Hydraulic
  Ram--The Double-acting Hydraulic Ram--Domestic Water-supply
  Plants--Gravity Water Supply--Pressure-tank System of Water
  Supply--The Pressure Tank--Power Water-supply Plants--Electric
  Power Water Supply--The Water Lift.


  SEWAGE DISPOSAL                                                  168

  The Septic Tank--The Septic Tank With a Sand-bed Filter--The Septic
  Tank and Anaerobic Filter--Limit of Efficiency.


  COAL                                                             182

  Oxidation of Hydrocarbons--Graphitic Anthracite--Cannel
  --Comparative Value of Coal to Other Fuels--Price of Coal.


  ATMOSPHERIC HUMIDITY                                             196

  Humidity of the Air--Relative Humidity--The Hygrometer--The
  Hygrodeik--Dial Hygrometers--The Swiss Cottage
  “Barometer”--Dew-point--To Determine the Dew-point--Frost
  Prediction--Prevention of Frost--Humidifying Apparatus.


  VENTILATION                                                      219

  Quantity of Air Discharged by a Flue--Cost of Ventilation--The
  Wolpert Air Tester--Pneumatic Temperature Regulation--Mechanical
  Ventilation--The Plenum Method--Ventilation Apparatus--Air
  Conditioning--Humidifying Plants--Vaporization as a Cooling
  Agent--Air-cooling Plants--Humidity Control.


  GASEOUS AND LIQUID FUELS                                         250

  Gaseous and Liquid Fuels--Coal Gas--All-oil Water Gas--Pintsch
  Gas--Blau Gas--Water Gas--Measurement of Gas--Gas Meters How
  to Read the Index--Prepayment Meters--Gas-service Rules--Gas
  Ranges--Lighting and Heating with Gasoline--Gasoline--Kerosene--The
  Cold-process Gas Machine--The Hollow-wire System of Gasoline
  Lighting and Heating--Mantle Gas Lamps--Open-flame Gas Burners--The
  Inverted-mantle Gasoline Lamp--Portable Gasoline Lamp--Central
  Generator Plants--Central-generator Gas Lamps--Boulevard
  Lamps--Gasoline Sad Irons--Alcohol Sad Irons--Alcohol Table
  Stoves--Danger from Gaseous and Liquid Fuels--Acetylene-gas
  Machine--Types of Acetylene Generators--Gas Lighters--Acetylene


  ELECTRICITY                                                      305

  Incandescent Electric Lamps--The Mazda Lamp--Candlepower--Lamp
  Labels--Illumination--The Foot-candle--The
  Lumen--Reflectors--Choice of Reflector--Lamp Transformers--Units
  of Electrical Measurements--Miniature Lamps--Effects of Voltage
  Variations--Turn-down Electric Lamps--The Dim-a-lite--Gas-filled
  Lamps--Daylight Lamps--Miniature Tungsten Lamps--Flash Lights--The
  Electric Flat-iron--The Electric Toaster--Motors, Fuse
  Plugs--Electric Heaters--Intercommunicating Telephones--Electric
  Signals--Buzzers--Burglar Alarms--Annunciators--Table
  Pushes--Bell-ringing Transformers--The Recording Wattmeter--To
  Read the Meter--State Regulation of Meter Service--Electric
  Batteries--Battery Formation--Battery Testers--Electric
  Conductors--Lamp Cord--Portable Cord--Annunciator Wire--Private
  Electric Generating Plants--Storage Batteries--The Pilot
  Cell--National Electrical Code--Electric Light Wiring--Outlet
  Boxes--Automatic Door Switch--Plug Receptacles--Heater Switch,
  Pilot and Receptacle--Service Switch--Local Switches--Pilot
  Lights--Wall and Ceiling Sockets--Drop Lights.

  INDEX                                                            385




The use of steam as a means of heating dwellings is common in every
part of the civilized world. Plants of all sizes are constructed, that
not only give satisfactory service but are efficient in the use of
fuel, and require the minimum amount of attention.

The manufacture of steam heating apparatus has come to be a distinct
industry, and represents a special branch of engineering. Many
manufacturing companies, pursue this line of business exclusively.
The result has been the development of many distinctive features and
systems of steam heating, that are very excellent for the purposes

Practice has shown that large plants can be operated more economically
than small ones. Steam may be carried through underground, insulated
pipes to great distances with but small loss of heat. This has lead to
the sale of exhaust steam, from the engines of manufacturing plants,
for heating purposes and the establishment of community heating plants,
where the dwellings of a neighborhood are heated from a central heating
plant; each subscriber paying for his heat according to the number of
square feet of radiating surface his house contains.

In the practice most commonly followed, with small steam heating
plants, the steam is generated in a boiler located at any convenient
place, but commonly in the basement. The steam is distributed through
insulated pipes to the rooms, where it gives up its heat to cast-iron
radiators, and from them it is imparted to the air; partly by radiation
but most of the heat is transmitted to the air in direct contact with
the radiator surface.

The heating capacity of a radiator is determined by its outside surface
area, and is commonly termed, _radiating surface_ or _heating surface_.
Radiators of different styles and sizes are listed by manufacturers,
according to the amount of heating surface each possesses. Radiators
are sold at a definite amount per square foot, and may be made to
contain any amount of heating surface, for different heights from 12 to
45 inches.

The widespread use of steam as a means of heating buildings is due to
its remarkable heat content. When water is converted into vapor the
change is attended by the absorption of a large amount of heat. No
matter at what temperature water is evaporated, a definite quantity of
heat is required to merely change the water into vapor without changing
its temperature. The heat used to vaporize water in a steam boiler is
given up in the radiators when the steam is condensed. It is because of
this property that steam is such a convenient vehicle for transferring
heat from the furnace--where it is generated--to the place to be
warmed. This heat of vaporization is really the property which gives to
steam its usefulness as a means of heating.

=Heat of Vaporization.=--The temperature of the steam is comparatively
an unimportant factor in the amount of heat given up by the radiator.
It is the heat liberated at the time the steam changes from vapor to
water that produces the greatest effect in changing the temperature of
the house. This evolution of heat by condensation is sometimes called
the latent heat of vaporization. It is the heat that was used up in
changing the water to vapor. The following table of the properties of
steam shows the temperatures and exact amounts of latent heat that
correspond to various pressures.

When water at the boiling point is turned into steam at the same
temperature, there are required 965.7 B.t.u. for each pound of water
changed into steam. In the table, this is the latent heat of the
vapor of water at 0, gage pressure. As the pressure and corresponding
temperature rise, the latent heat becomes less. At 10 pounds gage
pressure, the temperature of the steam is practically 240°F., but the
heat of vaporization is 946 thermal units. When the steam is changed
back into water, as it is when condensed in the radiators, this latent
heat becomes sensible and is that which heats the rooms. The steam
enters the radiators and, coming into contact with the relatively
colder walls, is condensed. As condensation takes place, the latent
heat of the steam becomes sensible heat and is absorbed by the
radiators and then transferred to the air of the rooms.


  Absolute |   Gage   | Temperature | Latent
  pressure | pressure |             |  heat
       0   |   14.7   |   212.00    |  965.70
       1   |   15.0   |   213.04    |  964.96
       2   |   16.0   |   216.33    |  962.63
       3   |   17.0   |   219.45    |  960.49
       4   |   18.0   |   220.40    |  958.32
       5   |   19.0   |   225.25    |  958.30
       6   |   20.0   |   227.95    |  954.38
       7   |   21.0   |   230.60    |  952.50
       8   |   22.0   |   233.10    |  950.62
       9   |   23.0   |   235.49    |  949.03
      10   |   24.0   |   237.81    |  947.37
      11   |   25.0   |   240.07    |  945.76
      12   |   26.0   |   242.24    |  944.25
      13   |   27.0   |   244.32    |  942.74
      14   |   28.0   |   246.35    |  941.29
      15   |   29.0   |   248.33    |  939.88
      16   |   30.0   |   250.26    |  938.50
      17   |   31.0   |   252.13    |  937.17
      18   |   32.0   |   253.98    |  935.45
      19   |   33.0   |   255.77    |  934.57
      20   |   34.0   |   257.52    |  933.32
      21   |   35.0   |   259.22    |  932.10
      22   |   36.0   |   260.88    |  930.92
      23   |   37.0   |   262.50    |  929.76
      24   |   38.0   |   264.09    |  928.62
      25   |   39.0   |   265.65    |  927.51

Whenever water is evaporated, heat is used up at a rate that in amount
depends on its temperature and the quantity of water vaporized.
This heat of vaporization is important, not only in problems which
relate to steam heating but in all others where vapor of water exerts
an influence--ventilation of buildings, atmospheric humidity, the
formation of frost, refrigeration, and many other applications in
practice; this factor is one of the important items in quantitative
determinations of heat. It will appear repeatedly in considering
ventilation and humidity.

At temperatures below the boiling point of water, the heat of
vaporization gradually increases until, at the freezing point,
it is 1092 B.t.u. Water vaporizes at all temperatures--even ice
evaporates--and the cooling effect produced by evaporation from
sprinkled streets in summer, or the chilling sensation brought about
by the winds of winter are caused largely because of its effect.
The evaporation of perspiration from the body is one of the means
of keeping it cool. At the temperature of the body 98.6 the heat of
vaporization is 1046 B.t.u.

=Steam Temperatures.=--While the temperature of steam is an unimportant
factor in the heating of buildings there are many uses in which it
is of the greatest consequence. When steam is employed for cooking
or baking it is not the quantity of heat but its intensity that is
necessary for the accomplishment of its purpose.

Steam cookers must work at a temperature suitable to the articles
under preparation, and the length of time required in the process.
Examination of the table on page 3, will show that steam at the
pressure of the air or 0, gage pressure, has a temperature of 212°F.,
which for boiling is sufficiently intense for ordinary cooking; but
for all conditions required of steam cooking, a pressure of 25 pounds
gage pressure is required. The temperature corresponding to 25 pounds
is shown in the table as 267°F. Baking temperatures for oven baking as
for bread requires temperatures of 400°F. or higher. To bake by steam
at that temperature would require a gage pressure of 185 pounds to the
square inch.

=The British thermal unit= is the English unit of measure of heat. It
is the amount of heat required to raise the temperature of a pound of
water 1°F. From the table it will be seen that steam at 10 pounds gage
pressure, is only 27.4° hotter than it was at 0 pounds. In raising the
pressure of a pound of steam from 0 to 10 pounds, the steam gained
only 27.4 B.t.u. of heat. The amount of heat gained by raising the
pressure to 10 pounds is small as compared with the heat it received on
vaporizing. The extra fuel used up in raising the pressure is not well
expended. It is customary, therefore, in heating plants, to use only
enough pressure in the boiler to carry the steam through the system.
This amount is rarely more than 10 pounds and oftener but 3 or 4 pounds

=Gage Pressure--Absolute Pressure.=--In the practice of engineering
among English speaking people, pressures are stated in pounds per
square inch, above the atmosphere. This is termed gage pressure. It
is that indicated by the gages of boilers, tanks, etc., subjected
to internal pressure. Under ordinary conditions the term pressure
is understood to mean gage pressure, the 0 point being that of the
pressure of the atmosphere. This system requires pressures below that
of the atmosphere to be expressed as a partial vacuum, a complete
vacuum being 14.7 pounds below the normal atmospheric pressure.

In order to measure positively all pressures above a vacuum, the normal
atmosphere is 14.7 pounds; all pressures above that point are continued
on the same scale, thus:

    Gage pressure  0 = 14.7 absolute
    Gage pressure 10 = 10 + 14.7 = 24.7 absolute
    Gage pressure 20 = 20 + 14.7 = 34.7 absolute

Absolute pressures are, therefore, those of the gage plus the
additional amount due to the atmosphere. All references to pressure in
this work are intended to indicate gage pressure unless specifically
mentioned as absolute pressure.

Steam heating as applied to buildings may be considered under two
general methods: the pressure system in which steam under pressure
above the atmosphere is utilized to procure circulation; and the
vacuum system in which the steam is used at a pressure below that of
the atmosphere. Each of these systems is used under a great variety of
conditions, and to some is applied specific names but the principle of
operation is very much the same in all of a single class.

Steam heating plants are now seldom installed in the average home
but they are very much employed in apartment houses and the larger
residences. In large buildings and in groups of buildings heated
from a central point, steam is used for heating almost exclusively.
The type of plant employed for any given condition will depend on
the architecture of the buildings and their surroundings. In very
large buildings and in groups of buildings, the vacuum system is very
generally employed. This system has, as a special field of heating, the
elaborate plants required in large units.

The low-pressure gravity system of heating is used in buildings of
moderate size, large residences, schools, churches, apartment houses,
and the like. Under this form of steam heating is to be included vapor
heating systems. This is the same as the low-pressure plant except
that it operates under pressure only slightly above the atmosphere and
possesses features that frequently recommend its use over any other
form of steam heating. The term vapor heating is used to distinguish it
from the low-pressure system.

=The low-pressure gravity system=, with which we are most concerned,
takes its name from the conditions under which it works. The low
pressure refers to the pressure of the steam in the boiler, which is
generally 3 or 4 pounds; and since the water of condensation flows back
to the boiler by reason of gravity, it is a gravity system.

The placing of the pipes which are to carry the steam to the radiators
and return the water of condensation to the boiler may consist of
one or both of two standard arrangements. They are known as the
_single-pipe system_ and the _two-pipe system_.

[Illustration: FIG. 1.--Diagram of a gravity system steam heating

Fig. 1 shows a diagram of a single-pipe system in its simplest form.
In the figure the pipe marked _supply and return_, connects the boiler
with the radiators. From the vertical pipe called a _riser_, the steam
is taken to the radiators through branch pipes that all slope toward
the riser, so that the water of condensation may readily flow back into
the boiler. The water of condensation, returning to the boiler, must
under this condition, flow in a direction contrary to the course of the
steam supplying the radiators. In Fig. 2 is given a simple application
of this system. A single pipe from the top of the boiler, in the
basement, marked _supply and return pipe_, connects with one radiator
on the floor above. The radiator and all of the connecting pipes are
set to drain the water of condensation into the boiler.

[Illustration: FIG. 2.--A simple form of steam heating plant. The
furnace fire is controlled by a thermostat and a damper regulator.]

When the valve is opened to admit steam to the radiator, the air vent
must also be opened to allow the escape of the contained air. The steam
will not diffuse with the air in the radiator and unless the air is
allowed to escape, the steam will not enter. As the steam enters the
cold radiator, it is rapidly condensed, and collects on the walls in
the form of dew, at the same time giving up its latent heat. The heat
is liberated as condensation takes place, and as the dew forms on the
radiator walls the heat is conducted directly to the iron. The water
runs to the bottom of the radiator and then through the pipes; back
to the boiler. The water occupies but relatively a little space and
may return through the same pipe, while more steam is entering the
radiator. As the steam condenses in the radiator, its reduction in
volume tends to reduce the pressure and thus aids additional steam from
the boiler to enter. In this manner a constant supply of heat enters
the radiator in the form of steam which when condensed goes back to the
boiler at a temperature very near the boiling point to be revaporized.
It should be kept in mind that it is the heat of vaporization, not the
temperature of the steam that is utilized in the radiator, and that the
heat of vaporization is the vehicle of transfer. The water returning to
the boiler may be at the boiling point and the steam supplying the heat
to the radiators may be at the same temperature.

[Illustration: FIG. 3.--A gravity system steam heating plant of two
radiators. The furnace is governed by a thermostat.]

Fig. 3 is a slightly different arrangement of the same boiler as that
shown in Fig. 2, connected with two radiators on different floors. The
same riser supplies both radiators with steam and takes the water of
condensation back to the boiler.

Fig. 4 is an example of the single-pipe system applied to a small
house. In the drawing, the boiler in the basement is shown connected
with four radiators on the first floor and three on the second
floor. The pipes connecting with the more distant radiators are only
extensions of the pipes connecting the radiators near the boiler. As
in Figs. 1, 2 and 3, all of the pipes and radiators are set to drain
back into the boiler. If at any place the pipe is so graded that a part
of the water is retained, poor circulation will result, because of the
restricted area of the pipe, and the radiators will not be properly
heated. This lack of drainage is also a common cause of hammering and
pounding in steam systems, known as _water-hammer_. The formation of
water-hammer is caused by steam flowing through a water-restricted
area, into a cold part of the system, where condensation takes place
very rapidly. The condensation of the steam is so rapid and complete
that the resulting vacuum draws the trapped water into the space with
the force of a hammer stroke. The hammering will continue so long as
the conditions exist. The pipes in the basement are suspended from the
floor joists by hangers as shown in the drawing. In practice the pipes
in the basement are covered with some form of insulating material to
prevent loss of heat.

[Illustration: FIG. 4.--The gravity system steam heating plant
installed in a dwelling.]

As stated above, the single-pipe system may be successfully used in all
house-heating plants except those of large size. It requires the least
amount of pipe and labor for installation of the circulating system and
when well constructed performs very satisfactorily all of the functions
required in a small heating plant.

One of the commonest causes of trouble in a single-pipe system is due
to the radiator connections. The single radiator connection requires
the entering steam and escaping water of condensation to pass through
the same opening. Under ordinary conditions this double office of the
radiator valve is accomplished with satisfaction but occasionally it
is the cause of considerable noise. At any time the valve is left only
partly open the steam will enter and condense because of the lower
pressure inside the radiator but the condensed water will not be able
to escape. The water has only the force of gravity to carry it out of
the radiators and if it meets no opposition will flow back through
the pipe to the boiler; but if it is required to pass a small opening
through which steam is flowing in a contrary direction, the water will
be retained in the radiators. Single-pipe radiators, therefore, work
satisfactorily only under conditions which will permit the steam to
enter and the water to leave as fast as it is formed. In ordinary use
the valve at any time is apt to be left slightly open and this produces
undesirable working conditions.

In larger buildings, where greater distances require longer runs
of pipe and more complicated connections, and where the volume of
condensed steam is too great to be taken care of in a single pipe, this
system does not work satisfactorily.

=Two-pipe System.=--Fig. 5 is a diagram of a two-pipe system. Here,
each radiator has a _supply pipe_, through which the steam enters, and
a _return pipe_ which conducts the water away. The branch pipes from
a common supply pipe or riser, carry steam to the various radiators
and all of the return pipes empty into a single return pipe that takes
the water back to its source. It will be noticed that in this case
the _riser_ also connects at the bottom with the return pipe. This
connection is made for the purpose of conducting away the condensation
that takes place in the connecting pipes. The water will always
stand in these pipes, at the same height as the water in the boiler.
The supply pipe from the boiler, and the branch pipes connecting
the radiators all slope toward the _riser_. The condensation in the
connecting pipes does not pass through the radiators as it returns to
the boiler.

An exception to this general rule is shown in the radiator on the
second floor. In this case the supply pipe slopes downward as it
approaches the radiator. To prevent carrying water through the
radiator, a small pipe under the left-hand valve connects with the
return pipe and the water is thus conducted to the main return pipe.

[Illustration: FIG. 5.--Diagram showing the arrangement of a two-pipe
steam plant.]

Fig. 6 is a simple application of the arrangement shown in Fig. 5.
The steam may be easily traced from the boiler to the radiators, and
back through the return pipes to its source. The pipe marked _R_ is
the connection between the main supply pipe and the return pipe that
takes away the condensation of the riser. It is connected to the main
return pipe below the water line of the boiler and, therefore, does
not interfere in any way with the passage of the steam. Each radiator
empties its water of condensation into a common return pipe, that
finally connects with the boiler below the water line.

[Illustration: FIG. 6.--A two-pipe steam heating plant.]

This arrangement may be elaborated to almost any extent and is an
improvement over the single-pipe system. It is quite commonly used as
a method of steam distribution, but it lacks the required elements
necessary to a positive circulation. As an example: Suppose that the
plant shown in Fig. 6 is working and that the radiator on the first
floor is hot, but the valves of the radiator on the second floor are
closed and it is cold. The steam entering at the valve _A_ of the lower
radiator is being condensed as fast as the heat is radiated. The steam
will pass on through the valve _B_ into the return pipe and as soon as
the return pipe becomes hot it will contain steam at practically the
same pressure as that in the supply pipe. This is what takes place in
every working steam plant. Now suppose that it is desired to heat the
radiator on the floor above. The steam valve _A_ of the upper radiator
is opened to admit steam and the return valve is also opened to allow
the water to escape. There is steam in both the supply and return pipes
of the radiator below at the same pressure, each tending to send steam
into the radiator above at opposite ends. This would make a condition
exactly the same as a single-pipe system, with a supply pipe at both
ends of the radiator and the result would, of course, be the same as in
the single-pipe system. There being no place for the water to escape
except against the incoming steam, the water will sometimes surge back
and forth with the customary noises peculiar to such conditions. It
must not be understood that this will always occur, because systems of
this kind are in use with fairly good results, but noisy radiators are
not at all rare when working under this condition and the cause is from
that described. To overcome this difficulty and change the system into
one in which there would be a positive circulation from _A_ to _B_, in
each radiator, allowing the steam always to enter at the valve _A_ and
escape at _B_, the system must be changed to that of _separate returns_.

[Illustration: FIG. 7.--Diagram of a separate return steam system.]

=Separate-return System.=--A diagram of a _separate-return_ system is
shown in Fig. 7. In this figure, the radiator, boiler and supply pipes
are the same as those of Fig. 5, but there is a separate return pipe
from each of the radiators, connecting with the main return pipe at a
point below the water line of the boiler. Examination of this diagram
will show that there is an independent circuit for the steam through
each radiator. The steam is taken from a common riser as before but
after passing through the radiator the water is returned by a separate
pipe to the main return pipe at the bottom of the boiler. Fig. 8 is an
application of _separate-return_ system. It is exactly the same as Fig.
6, except that each radiator has an independent return pipe. Steam must
always enter the radiators at the valves _A_ and leave at the valves
_B_. This makes a positive circulation that renders each radiator
independent of the others. There is no opportunity for steam to pass
through one radiator and interfere with the return water of another;
it, therefore, prevents the possibility of hammering or surging so
common in poorly designed steam systems.

Of all the methods of steam heating where the water of condensation
is returned to the boiler by reason of gravity this is the most
satisfactory. This plant requires a larger amount of pipe than the
other systems described and as a consequence the cost of installation
is greater but it repays in excellence of service the extra expense

[Illustration: FIG. 8.--A separate return heating plant.]

=Overhead or Drop System.=--There is yet another gravity system of
steam heating that is sometimes used in large buildings where economy
in the use of pipe is desired; this is the _overhead_ or _drop_ system
shown in Fig. 9. It is not a common method of piping and is given here
only because of its occasional use. In the arrangement of the _drop_
system, the supply pipe for the radiators rises from the boiler to the
highest point of the system and the branch pipes for the radiators are
taken off from the descending pipe. Its action is the same as that of
a single-pipe system but the advantage gained by the arrangement is
that the steam in the main supply pipes travels in the same direction
as the returning water of condensation; the cause of _surging_ in long
_risers_ is thus eliminated.

The two-pipe systems of steam heating are more certain in action than
the single-pipe methods because there is nothing to interfere with
the progress of the steam on its way to the radiators. In long branch
pipes of the _single-pipe_ system, the returning water is frequently
caught by the advancing steam and carried to the end of the pipe, when
_slugging_ and _surging_ is the result.

[Illustration: FIG. 9.--Diagram of the overhead or drop system steam

=Water-filled Radiators.=--Radiators frequently fill with water and are
noisy because of the position of the valve. This may be true in any
gravity system but particularly so in radiators having a single pipe.
When the valve of a single-pipe radiator is opened a very small amount,
the entering steam is immediately condensed but the water cannot escape
because the incoming steam entirely fills the opening. Under this
condition, the radiator may entirely fill with water. If the valve is
then opened wide, the imprisoned water has an opportunity to escape
while the steam is entering, but the entering steam and escaping water
sets up a water-hammer that sometimes is terrific and lasts until the
water is discharged from the radiator. The same condition may exist
in a two-pipe system, if the steam valve is slightly opened while the
escape valve is closed, but in a well-designed system the radiator will
be immediately emptied when both valves are open.

=Air Vents.=--All radiators must be provided with air vents. The
vent is placed near the top of the last loop of the radiator, at the
end opposite from the entering steam, as indicated in Figs. 2, 3, 6,
etc. The object of the vent is to allow the air to escape from the
radiator as the steam enters. Steam will not diffuse with the air and,
therefore, cannot enter the radiator until the air is discharged.
The air vent may be a simple cock such as is shown in Fig. 10, that
must be opened by hand when the steam is turned on, to allow the air
to escape, and closed when the steam appears at the vent; or it may
be an automatic vent, that opens when the radiator cools and closes
automatically when the radiator is filled with steam. There are many
makes of air vents of both hand-regulating and automatic types; of
the former, Fig. 10 furnishes a common example. The part _A_, in the
figure, is threaded and screws tightly into a hole made to receive it
in the end loop of the radiator. The part _B_ is a screw-plug that
closes the passage _C_, leading to the inside of the radiator. When
the steam is turned on, the vent must be opened until the air is
discharged, after which it is closed by the hand-wheel _D_.

[Illustration: FIG. 10. FIG. 11. FIG. 12. FIG. 13.

FIG. 10.--A common form of air vent for radiators.

FIG. 11.--An inexpensive automatic radiator air vent.

FIG. 12.--Monash No. 16 automatic air vent.

FIG. 13.--The Allen float, radiator air vent.]

=Automatic Air Vents.=--These vents depend for their action on the
expansion of a part of the valve due to the temperature of the steam.
The valve remains closed when hot and opens when cold. The difference
in temperature between the steam and the expelled air from the radiator
is the controlling factor. In the automatic vent shown in Fig. 11, the
part _A_ is screwed into the radiator loop. The discharge _C_ is open
to the air or connected with a drip pipe, which returns the water to
the basement. The cylinder _D_, which closes the passage _B_, is made
of a material of a high coefficient of expansion. The piece _D_, when
cool, is contracted sufficiently to leave the passage _B_ open to the
air. When the steam is turned on, the expelled air from the radiator
escapes through _B_ and _C_, but when the steam reaches _D_ the heat
quickly expands the piece and closes the vent.

Most automatic vents require adjusting when put in place and
occasionally need readjustment. The cap _O_, of Fig. 11, may be removed
with a wrench and a screw-driver used to adjust the piece _D_, so as
to shut off the steam when the radiator is filled with steam. The
expanding piece is simply screwed down until the steam ceases to escape.

Fig. 12 is another style of automatic vent, constructed on the same
principle as that of Fig. 11, but probably more positive in action. In
this vent the part _A_ attaches to the radiator. The expanding portion
_B_ is made in the form of a hollow cylinder, through which the air and
steam escape to the atmosphere. It is longer than the corresponding
piece in the other vent and is more sensitive because of its greater
length and exposed surface. As the piece _B_ elongates from expansion,
the upper end makes a joint with the conical piece _D_. The shape of
this latter piece gives better opportunity for a tight joint than in
the other form of vent and in practice gives better service.

Fig. 13 is a cross-section of the Allen vent. This is an example of a
vent which depends for its action on a float. Whenever sufficient water
accumulates in the body of the vent to raise the float, it closes the
vent by means of its buoyancy. The body of the vent shown in Fig. 13 is
composed of two concentric cylinders. The float _E_ occupies the inner
cylinder, while surrounding it is the outer cylinder _D_. The outer
cylinder is entirely closed except a little hole at _G_. The float is
made of light metal and fits loosely in the inner cylinder. The steam
from the radiator condenses in the vent until the inner cylinder is
filled with water, up to the opening _A_. The float by its buoyancy
keeps the opening in _B_ stopped, and no steam can escape. The air of
the outer cylinder _D_ is expanded by the heat of the steam and most
of the air escapes through the hole _G_. When the radiator cools,
the rarefied air in _D_ contracts and draws the water from the inner
cylinder into the space _D_; this allows the float to fall and unstop
the opening in _B_. When the steam again reaches the vent, the heat
expands the air in _D_ and forces the water into the inner cylinder;
the float is again raised and stops the opening in _B_.

Many other air vents are in common use but most of them operate on
one or the other of the principles described. Fig. 11 is a relatively
inexpensive vent, while Fig. 12 is higher-priced.

[Illustration: FIG. 14.--Steam radiator valve.

FIG. 15.--Sectional view of a steam radiator valve.]

=Steam Radiator Valves.=--Like most other mechanical appliances that
are extensively used, radiator valves are made by a great number
of manufacturers and in many different forms. Some possess special
features that are intended to increase their working efficiency but the
type of radiator valve most commonly used for ordinary construction is
that illustrated in Figs. 14 and 15. It is a style of _angle valve_
that takes the place of an elbow and being made with _a union joint_,
also furnishes a means of disconnecting the radiator without disturbing
the pipes. Fig. 14 is an outside view of the valve and Fig. 15 shows
its mechanical construction. The part _B_ screws onto the end of the
steam pipe and _A_ connects with the radiator. The part _C-D_ is the
_union_. The nut _C_ screws onto the valve and makes a steam-tight
joint at _D_, between the parts. In case it is desired to remove the
radiator, it furnishes an easy means of detaching the valve. The
composition valve-disc _E_ makes a seat on the brass ring directly
under it, to shut off the steam. In case the valve leaks, the disc may
be removed by taking the valve casing apart at _G_. The worn disc can
then be replaced with a new one which may be obtained from the dealer
who furnished the valve. The only moving part of the valve exposed to
the air is at the point where the valve-stem _S_ enters the casing. The
joint is made steam-tight by the packing _P_. The packing is greased
candle wicking that is wound around the stem and held tightly in place
by the screw-cap _H_. If the valve leaks at this joint, a turn or two
with a wrench will stop the escape of the steam.


House-heating boilers were formerly made of sheet metal and are still
so constructed to some extent, but by far the greater number are now
made of cast iron. Sheet-metal boilers are constructed at the factory,
ready to be installed, but the cast-iron type is made in sections
and assembled to make a complete boiler, at the time the plant is
erected. Sectional boilers are convenient to install, on account of the
possibility of handling the parts in a limited space, that would not
admit an assembled boiler without tearing down a part of the basement
for admission.

Cast-iron boilers as commonly used for heating dwellings are made in
two definite styles. The small sizes are cylindrical in form and are
used for either steam or hot-water heating. The larger sizes are made
as illustrated in Figs. 16 and 17, the former being an outside view,
and the latter showing the internal arrangement of the same boiler. The
fire-box, water space and smoke passages are easily recognized. Each
division represents a separate section which assembled as that in the
figures makes a complete boiler with a common opening as shown at the
top of Fig. 17. These boilers are used for residences of large size and
for buildings of less than 10,000 feet of radiating surface. For large
buildings, the steam is most commonly generated in boilers built for
high pressure.

In small plants, intended for either steam or hot-water heating,
the cylindrical style of boiler shown in Fig. 18 is commonly used.
As constructed by different manufacturers, the parts differ quite
materially but Fig. 18 shows all of the essential features and serves
to illustrate the different working parts. The sections into which the
boiler is divided are indicated on the left-hand side of the figure by
the numbers 1 to 6. The parts from 1 to 5 are screwed together with
threaded nipples, joining the central column. The part 6 contains the
grate and the ash-pit, with the draft and clean-out doors.

[Illustration: FIG. 16. FIG. 17.

FIG. 16.--Sectional cast-iron boiler for steam or hot-water heating.

FIG. 17.--Interior view of the boiler shown in Fig. 16.]

The drawing shows the boiler cut through the middle lengthwise and
exposes to view all of the essential features. The fire-box and the
spaces occupied by the steam and water are easily recognized. It will
be seen that the water space surrounds the fire-box except at the
bottom and that the space above the fire-box presents a large amount
of heating surface to the flame and heated gases as they pass to the
chimney. The arrows show their course; first through the openings near
the center, then through those further away. The object being to keep
the heat as long as possible in contact with the heating surfaces
without interfering with the draft.

[Illustration: FIG. 18.--Sectional view of the cylindrical type of
cast-iron, sectional boiler.]

There is no standard method of rating the heating capacity of boilers
of this kind and as a consequence, boilers of different makes--for the
same rating--are not the same in actual heating capacity. The boilers
are sold by their makers in sizes that are intended to furnish heat
sufficient to supply a definite number of square feet of radiating
surface. The ratings are quite generally too high for the weather
conditions of the Northwest. A common practice with contractors is to
select boilers for a given plant 50 per cent. and even 100 per cent.
larger than those rated by the manufacturers for the same amount of
radiation. Some manufacturers sell their boilers at honest ratings but
they are exceptions.

In specifying the capacity of a house-heating plant it is common
practice to require the boiler to be of such size as will easily heat
a definite number of square feet of radiating surface. The radiators
are required to possess sufficient radiating surface to keep the house
at 70°F. in any weather. In the absence of any rules or specifications
for determining the heating capacity of the boiler, the only means
of securing a satisfactory plant is to require a guarantee of the
contractor to install a boiler such as will fulfil the conditions
stated above.

=Boiler Trimmings.=--Attached to the boiler and required for its safe
operation are a number of appliances that demand special attention. The
office of each part should be thoroughly appreciated and the mechanical
construction should be fully understood. An intimate acquaintance with
the details of the plant, helps to make its operation satisfactory and
adds to the efficiency with which it can be made to perform its duty.

=The Water Column.=--In Fig. 18 the water column is shown at _C_.
It is attached to the boiler by pipes at points above and below the
water line, so as to allow a free passage of the water of the boiler
to the interior. The water line should be 3 or 4 inches above the top
heating surface. Attached to the water column is the _gage-glass_, the
_try-cocks_ _T_ and _T_ and the _steam gage_ _G_.

The object of the gage-glass is to show the height of the water in the
boiler. It is shown in place on the boiler in Figs. 16 and 18 and in
detail in Fig. 19. The lower part of the gage-glass occupies a position
on the boiler about 2 inches above the top heating surface. When the
boiler is working, the level of the water should always be visible in
the glass and should stand normally one-third to one-half full.

[Illustration: FIG. 19.--The water gage.]

The water gage is attached to the water column by two brass valves
_V_. The valves are provided so that in case the water glass should
be broken the openings may be closed. The ends of the glass are made
tight by “stuffing-boxes” marked _C_, in the figure. The packing _S_ is
generally in the form of rubber rings but greased wicking may be used
if necessary as in the case of valve-stems.

_The try-cocks_ _T_ and _T_ (Fig. 18) are also intended to indicate
the approximate height of the water in the boiler and should the
water glass be broken may be used in its place. The openings of the
try-cocks point toward the floor. When a cock is opened, should steam
alone escape, it will be absorbed by the air, but if water is escaping,
although much of it will be vaporized and look like steam, some of
the water will be carried to the floor and produce a wet spot. When
the cock is opened wide the escaping water from the lower cock should
always wet the floor.

_The drip-cock_ _P_ (Fig. 18) at the bottom of the gage-glass is for
draining the water column and for blowing out any deposit that may
collect in the opening of the column. This cock should be opened
occasionally to assure the correctness of the gage-glass.

[Illustration: FIG. 20.--Typical Bourdon pressure gage with the face

=The Steam Gage.=--Steam pressure is measured in pounds to the
square inch above the pressure of the atmosphere. The gages used for
indicating the pressure of the steam are made in several forms but
the type most commonly used is that shown in Fig. 20. It is known as
the Bourdon type of gage and takes its name from the bent tube _A_,
which furnishes its active principle. The Bourdon barometer invented
in 1849 employed this form of sensitive tube. In the drawing the face
of the gage has been removed to show the working parts. The sensitive
part is the flat elastic tube _A_, which is bent in the form of a
circle. When the pressure of the steam enters at _S_ the air in the
tube is compressed and the tube tends to straighten. The movement of
the tube caused by the steam pressure is communicated to the pointer
by a link connection and gear as shown in the drawing. The amount of
straightening of the tube will be in proportion to the steam pressure
and is indicated by the numbers marked on the face of the gage. When
the pressure is released, the tube returns to its original position
and the spiral spring _C_ turns the hand back to its first position.

[Illustration: FIG. 21.--Cross-section of a pop valve.]

=The Safety Valve.=--All steam boilers should be provided with safety
valves as a safeguard against excessive steam pressures. Of the various
types of safety valves, that known as the _pop-valve_ is most commonly
used on house-heating boilers. It is indicated at _W_ in Fig. 18 and
is shown in section in Fig. 21. The part _A_ is screwed into the top
of the boiler at any convenient place. The pressure of the spring _C_
holds the valve _B_ on its seat until the internal pressure reaches a
certain intensity at which the valve is set, when it opens and allows
the excess steam to escape. When the pressure is reduced, the spring
forces the valve back on its seat. The handle _D_ permits the valve to
be lifted at any time as an assurance that it is in working order. This
should be done occasionally, as the valve may stick to the seat after
long standing and allow the pressure to rise above the point at which
it should “pop.”

The valve may be set to “blow off” at any desired pressure by the
adjusting piece _E_. House-heating boilers generally have their safety
valves set to blow off at 8 or 10 pounds.

=The Draft Regulator.=--As a means of automatic control of the steam
pressure, the draft regulator is frequently used to so govern the fire
that when a certain steam pressure is reached, the direct draft will
be automatically closed and the check-draft damper opened. The draft
regulator is shown in place at _D_ in Fig. 18, and will also be found
in Fig. 16. A detailed description of the regulator will be found on
pages 60 and 61.


Rules for determining the amount of radiating surface that will
be required to satisfactorily heat a building to 70°F. regardless
of weather conditions are entirely empirical, that is, they are
derived from experience. It is evident that no definite rule can
be established that will take into account the method of building
construction, the kind and amount of materials that make up the walls
and the quality of workmanship employed. These variable quantities
coupled with the changing climatic conditions of temperature and wind
velocity produce a complication that cannot be overcome in a formula
that will give exact results.

Many rules are in use for this purpose, no two of which give exactly
the same results when applied to a problem. A common practice is to
apply one of the rules in use and then under conditions of exceptional
exposure, to add to the amount thus calculated as experience may

The following rule by Professor R. G. Carpenter of Cornell University
was taken from a handbook published by the J. L. Mott Iron Works of New
York. This company manufactures and deals in all kinds of apparatus
entering into steam and hot-water heating and the rule is given as one
that has produced satisfactory results.

RULE.--Add the area of the glass surface in the room to one-quarter
of the exposed wall surface, and to this add from one-fifty-fifth
to three-fifty-fifths of the cubical contents (one-fifty-fifth for
rooms on upper floor, two-fifty-fifths for rooms on first floor and
three-fifty-fifths for large halls); then for steam multiply by 0.25,
and for hot water by 0.40.

_Example._--A room 20 by 12 by 10 feet with glass exposure of 48 feet,
1/4 of wall exposure (two sides exposed) 320 feet = 80, 1/55 of 2400 =

      48 + 80 + 44 = 172 × 0.25 = 43 feet.
    If you add 2/55 the surface would be 54 feet.
    If you add 3/55 the surface would be 65 feet.


For any size system of steam or water heating the following rule will
be found entirely satisfactory for mains 100 feet long; for each 100
feet additional use a size larger ratio.


    _r_ = (3.1416/_d_)_R_ = _a_/_r_ × 100.

_r_ represents ratio of main in inches for each 100 feet of surface;
_d_, diameter of pipe; _R_, quantity of radiation carried by size of
pipe; _a_, area of pipe in inches.

From this the following table has been constructed:

    Diameter |  Area   | Ratio to | Quantity of
    of pipe  | of pipe | each 100 | radiation, steam
             |         | feet of  | or water, on a
             |         | surface  | given size pipe
      1½     |  1.767  |   2.10   |       84
      2      |  3.141  |   1.57   |      200
      2½     |  4.908  |   1.25   |      400
      3      |  7.069  |   1.04   |      700
      3½     |  9.621  |   0.90   |    1,062
      4      | 12.566  |   0.78   |    1,590
      4½     | 15.904  |   0.70   |    2,272
      5      | 19.625  |   0.63   |    3,120
      6      | 28.274  |   0.52   |    5,440
      7      | 38.484  |   0.45   |    8,550
      8      | 50.265  |   0.40   |   12,556
      9      | 63.617  |   0.35   |   18,100
     10      | 78.540  |   0.30   |   25,300


Radiators are much the same in appearance for both steam and hot-water
heating. They are hollow cast-iron columns so designed that they may
be fastened together in units of any number of sections. The sections
are made in size to present a definite number of square feet of outside
surface that is spoken of as radiating surface. The amount of radiating
surface in any radiator depends on its height and the contour of the
cross-section. The radiator sections may be made in the form of a
single column as Fig. 22 or they may be divided into two, three, four
or more columns to increase their radiating surface.

The following table, taken from a manufacturer’s catalogue, shows the
method of rating the heating capacity of a particular design. In the
table, the first column gives the number of sections in the radiator,
the second column states the length of the radiator in inches. The
columns headed heating surface give the heights of the sections in
inches and the amount of radiating surface in various radiators of
different heights and numbers of sections. As an example: This table
refers to the three-column radiators of Fig. 23. Such a radiator 32
inches high with 10 sections would contain 45 square feet of radiating
surface and would be 25 inches in length.

          |        |             Heating surface--square feet
          |        +--------+--------+--------+--------+--------+-------
   No.    | Length | 45 in. | 38 in. | 32 in. | 26 in. | 23 in. | 20 in.
   of     | 2½ in. | high,  | high,  | high,  | high,  | high,  | high,
  sections| per    | 6 sq.  | 5 sq.  | 4½ sq. | 3¾ sq. | 3¼ sq. | 2¾ sq.
          | section| ft.    | ft.    | ft.    | ft.    | ft.    | ft.
          |        | per    | per    | per    | per    | per    | per
          |        | sec.   | sec.   | sec.   | sec.   | sec.   | sec.
      2   |    5   |   12   |   10   |    9   |    7½  |    6½  |   5½
      3   |    7½  |   18   |   15   |   13½  |   11¼  |    9¾  |   8¼
      4   |   10   |   24   |   20   |   18   |   15   |   13   |  11
      5   |   12½  |   30   |   25   |   22½  |   18¾  |   16¼  |  13¾
      6   |   15   |   36   |   30   |   27   |   22½  |   19½  |  16½
      7   |   17½  |   42   |   35   |   31½  |   26¼  |   22¾  |  19¼
      8   |   20   |   48   |   40   |   36   |   30   |   26   |  22
      9   |   22½  |   54   |   45   |   40½  |   33¾  |   29¼  |  24¾
     10   |   25   |   60   |   50   |   45   |   37½  |   32½  |  27½
     11   |   27½  |   66   |   55   |   49½  |   41¼  |   35¾  |  30¼
     12   |   30   |   72   |   60   |   54   |   45   |   39   |  33
     13   |   32½  |   78   |   65   |   58½  |   48¾  |   42¼  |  35¾
     14   |   35   |   84   |   70   |   63   |   52½  |   45½  |  38½
     15   |   37½  |   90   |   75   |   67½  |   56¼  |   48¾  |  41¼
     16   |   40   |   96   |   80   |   72   |   60   |   52   |  44
     17   |   42½  |  102   |   85   |   76½  |   63¾  |   55¼  |  46¾
     18   |   45   |  108   |   90   |   81   |   67½  |   58½  |  49½
     19   |   47½  |  114   |   95   |   85½  |   71¼  |   61¾  |  52¼
     20   |   50   |  120   |  100   |   90   |   75   |   65   |  55
     21   |   52½  |  126   |  105   |   94½  |   78¾  |   68¼  |  57¾
     22   |   55   |  132   |  110   |   99   |   82½  |   71½  |  60½
     23   |   57½  |  138   |  115   |  103½  |   86¼  |   74¾  |  63¼
     24   |   60   |  144   |  120   |  108   |   90   |   78   |  66
     25   |   62½  |  150   |  125   |  112½  |   93¾  |   81¼  |  68¾
     26   |   65   |  156   |  130   |  117   |   97½  |   84½  |  71½
     27   |   67½  |  162   |  135   |  121½  |  101¼  |   87¾  |  74¼
     28   |   70   |  168   |  140   |  126   |  105   |   91   |  77
     29   |   72½  |  174   |  145   |  130½  |  108¾  |   94¼  |  79¾
     30   |   75   |  180   |  150   |  135   |  112½  |   97½  |  82½
     31   |   77½  |  186   |  155   |  139½  |  116¼  |  100¾  |  85¼
     32   |   80   |  192   |  160   |  140   |  120   |  104   |  88

Fig. 22 is a radiator made up of eight single-column sections. In Fig.
23 is shown five three-column radiators, varying in height from 20 to
45 inches.

The sections of steam radiators are joined together at the bottom
with _close-nipples_, so as to leave an opening from end to end. The
sections of hot-water radiators are joined in the same manner, except
that there is an opening at both top and bottom. Fig. 30 shows the
openings of a hot-water radiator installed as _direct-indirect_ heater.
Fig. 24 illustrates a special form of radiator that is intended to be
placed under windows and in other places that will not admit the high
form. Such a radiator as that shown in the picture is often covered
with a window seat and in cold weather becomes the favorite place of
the sitting room. Another special form is that of Fig. 25. As a corner
radiator this style is much to be preferred to the ordinary method of
connection; here the angle is completely filled--there is no open space
in the corner.

[Illustration: FIG. 22. FIG. 23.

FIG. 22.--Single column steam radiator.

FIG. 23.--Three-column radiators of different heights; for steam or
hot-water heating.]

Wall radiators such as shown in Fig. 26 are made to set close to the
wall, where floor space is limited. They are particularly adapted for
use in narrow halls, bathrooms and other places where the ordinary type
could not be conveniently used.

A radiator that will appeal to all neat housekeepers is that of Fig.
27. It does not stand on the floor as in the case of the ordinary
type, but is hung from the wall by concealed brackets. The difficulty
of sweeping under this radiator is entirely avoided.

Fig. 28 is a radiator designed to furnish a warming oven for plates and
for heating the room at the same time. It is sometimes installed in
dining rooms.

[Illustration: FIG. 24.--Six-column, low form of hot-water radiators to
be placed under windows.]

[Illustration: FIG. 25.--Two-column corner radiator for steam heating.]

[Illustration: FIG. 26.--Wall form, radiator for steam or hot water.]

The ordinary method of heating by the use of radiators is known as the
_direct_ method. The air is heated by coming directly into contact with
the radiators and distributed through the room by convection. If the
arrangement is such that the air is brought from outdoors and heated
by the radiator before entering the room, it is called the _indirect_
method of heating. Such an arrangement is illustrated in Fig. 29. The
radiator is located beneath the floor, in a passage that takes the
air from outdoors and after being heated, enters the room through a
register located in the wall.

Fig. 30 is still another arrangement known as the _direct-indirect_
method of heating. The radiator is placed in position, as for direct
heating, but the air supply is taken from outdoors. The radiator base
is enclosed and a double damper _T_ regulates the amount of air that
comes from the outside. When the inside damper is closed and the
outside damper is open, as is shown in the drawing, the air comes from
outdoors and is heated as it passes through the radiator on its way to
the room. If the dampers are reversed, the air circulates through the
radiator as in the case of direct radiation.

[Illustration: FIG. 27.--Two-column radiator suspended from the wall by

[Illustration: FIG. 28.--Dining-room radiator containing a warming

In the use of the _direct_ or the _direct-indirect_ method of heating
the principal object to be attained is that of ventilation, but quite
generally the passages are so arranged that the air may be taken from
outdoors or, if desired, the air of the house may be sent through the
radiators to be reheated. In extremely cold and windy weather it is
sometimes difficult to keep the house at the desired temperature when
all of the air supply comes from the outside. Under such conditions the
outside air is used only occasionally. In mild weather it is common to
use the outdoor air most of the time. The cost of heating, when these
methods are used, is higher than by direct radiation, because the air
is being constantly changed in temperature from that of the outside to

[Illustration: FIG. 29.--Ventilation by the indirect method of heating.]

[Illustration: FIG. 30.--Ventilation by the direct-indirect method of

=Radiator Finishings.=--In steam and hot-water heating the decoration
of the radiators is a much more important item than that of a
good-looking surface or one which will harmonize with the setting.
Until recently radiator finishing has been considered a minor detail
and the familiar bronze has been looked upon as a standard covering,
while painted radiators were considered only a matter of taste. The
character of the surface is, however, the determining factor in the
quantity of heat given out by radiators. This has been determined in
the experimental laboratory of the University of Michigan by Professor
John A. Allen. Comparison was made of bare cast-iron radiators with
the same forms painted as indicated in the following table. The bare
radiator was taken at 100 per cent.; the other finishes are expressed
in per cent. above or below that of the bare radiator.

                                                               per cent.

  No. 1, a cast-iron radiator, bare as received from the foundry    100
  No. 2, a cast-iron radiator, coated with aluminum bronze           78
  No. 3, a cast-iron radiator, three coats of white enamel paint    102
  No. 4, a cast-iron radiator, coated with copper bronze             80
  No. 5, a cast-iron radiator, three coats of green enamel paint    101
  No. 6, a cast-iron radiator, three coats of black enamel paint    101

The author has stated further that, “It might be said in general that
all bronzes reduce the heating effect of the radiator about 25 per
cent. while lead paints and enamels give off the same amount of heat
as bare iron. The number of coats of paint on the radiator makes no
difference. The last coat is always the determining factor in heat


All hot-water or steam pipes in the basement and in other places not
intended to be used for heating should be covered with some form of
insulating material. At ordinary working temperature a square foot of
hot pipe surface will radiate about 15 B.t.u. of heat per minute. To
prevent this loss of heat and the consequent waste of fuel the pipes
should be covered with some form of insulating material.

Pipe coverings are made of many kinds of material and some possess
insulating properties that may reduce the loss to as low a point as 15
per cent. of the amount radiated by a bare pipe. Many good insulating
materials do not give satisfactory results as pipe coverings because
they do not keep their shape, some cannot be considered in the average
plant because of high cost.

Wood-pulp paper is extensively used as a cheap covering; it is a good
insulator and under ordinary conditions makes a satisfactory covering.
A more efficient and also a more expensive covering that is extensively
used is that made of magnesia carbonate and known as magnesia covering.
Aside from these, other forms made of cork, hair-felt, asbestos and
composition coverings are sometimes used in house-heating plants.

In selecting a pipe covering, there should be taken into account not
only its insulating properties but its ability to resist fire, dampness
or breeding places for vermin. It rests entirely with the owner whether
he covers the pipes with a combustible or an incombustible material
when the insulating properties are about the same. Coverings made of
animal or vegetable materials under some conditions furnish a breeding
place for vermin.

Pipe coverings are made in sections about 3 feet in length and from 1
to 1-3/8 inches in thickness. The sections are usually cut in halves
lengthwise to permit being put in place. The sections are covered with
common muslin to keep the material in place and sometimes are painted
after being installed. Painting has nothing to do with their insulating
capabilities, but it preserves the cloth and makes a neat appearance.
The sections when put in place are secured by pasting one of the loose
edges of the cloth to the surface. The ends of the sections are bound
together with strips of metal. Fig. 31 shows the appearance of the pipe
when the covering is in place.

[Illustration: FIG. 31.--Pipe covering.]

Irregular surfaces like the body of the furnace, pipe connections,
etc., are insulated by coverings made from a plaster that is made
expressly for such work. It is known as asbestus plaster. The plaster
may be purchased in bulk and put in place with a trowel. As it is found
in the market the plaster requires only the addition of water to put
into working form.

The value of a pipe covering is not in proportion to its thickness.
Experiments with pipe coverings have shown that a thickness of 1-3/8
inches will reduce the radiation 90 per cent., but doubling the
thickness reduces the loss only 5 per cent. It, therefore, does not pay
to make a covering more than 1-3/8 inches thick.

=Vapor-system Heating.=--This system of heating is not greatly
different from the steam plants already described but it is operated
under conditions which do not permit the steam in the boiler to rise
beyond a few ounces of pressure. Since the plant is intended to work
at a pressure that is scarcely indicated by an ordinary steam gage, it
has been termed a _vapor system_ to distinguish it from the pressure
systems which employ steam, up to 5 pounds or more to the square inch.
The heat is transmitted to the radiators in the same manner as in the
pressure systems. The heat of vaporization of steam is somewhat greater
at the boiling point of water than at higher pressures, and the lack
of pressure, therefore, increases its heating capacity. This is shown
in the table, properties of steam, on page 3. The successful operation
of such a plant rests in the delivery of the vapor to the radiators at
only the slightest pressure and the return of the condensate to the
boiler without noise or obstruction to the circulation at the same time
ejecting the contained air.

The excellence of the system depends in the greatest measure on good
design and the employment of special facilities that allow all water
to be discharged from the radiators and returned to the boiler without
accumulation at any part of the circulating system. It requires,
further, the discharge of the air from the system at atmospheric
pressure. The system is, therefore, practically pressureless.

Various systems of vapor heating are sold under the names of their
manufacturers. Each possesses special appliances for producing positive
circulation that are advocated as features of particular excellence.
The vapor system of heating has met with a great deal of favor as a
more nearly universal form of heating than either the pressure-steam
plant or the hot-water method of heating.

Fig. 31_a_ is a diagram illustrating the C. A. Dunham system of
vapor heating. It will be noticed that there are no air vents on the
radiators. The air from the radiators is ejected through a special
form of trap that is indicated in the drawing. These traps permit
the water and air to pass from the radiators but close against the
slightly higher temperature of the vapor. This assures the condensation
of the vapor in the radiators and excludes it from the return pipes.
The water returns to the boiler in much the same manner as in the
pressure systems already described but the air escapes through the air
eliminator as indicated in the drawing. The system is, therefore, under
atmospheric pressure at this point and only a slight amount greater in
the boiler.

[Illustration: FIG. 31_a_.--Diagram showing the C. A. Dunham Co.’s
system of vapor heating.]

The water of condensation is returned to the boiler against the vapor
pressure, by a force exerted by the column of water in the pipe
connecting the air eliminator with the boiler. The main return is
placed 24 inches or more above the water line of the boiler. It is the
pressure of this column that forces the water into the boiler through
the check valve, against the vapor pressure in the boiler.

It might be imagined that the water in the boiler and that in the
air-eliminator pipe formed a “U-tube,” the vapor pressure on the water
surface in the boiler, and the atmospheric pressure on the water in
the eliminator standpipe. The slight vapor pressure in the boiler is
counterbalanced by a column of water in the eliminator pipe. It is this
condition that fixes a distance of 24 inches from the water line to the
return pipe; that is, the force exerted by a column of water 24 inches
high is required to send the water into the boiler.

The vapor pressure is controlled by means of the pressurestat, which
is an electrified Bourdon spring pressure gage, connected up by
simple wiring to the damper motor, which may be any form of damper
regulator. In residential work, the pressurestat is so connected with a
thermostat, that both pressure and temperature conditions operate and
control this damper regulator, which in turn controls the draft and the

The two instruments are so connected that if the pressure mounts to 8
ounces and the pressurestat caused the draft damper to close and the
check to open, the thermostat cannot reverse the damper, regardless
of the temperature in the room, until the pressure drops below the
limiting 8-ounce pressure. Just so long as the pressure is below 8
ounces, the thermostat is the master in the control of the dampers.
The minute that the pressure goes up to 8 ounces then the pressurestat
takes control.



Of the various systems of heating dwellings that by hot-water is
considered by many to be the most satisfactory. On account of its high
specific heat, water at a temperature much below the boiling point
furnishes the heat necessary to keep the temperature of the house at
the desired degree. The temperature of the radiators is generally much
lower than those heated by steam but the amount of radiating surface
is greater than for steam heating plants of the same capacity. It is
because of the relatively low temperature at which the water is used,
that the greater amount of heating surface is required.

One objection to the use of hot water as a means of heating is, that
once the heat of the house is much reduced, the furnace is a long time
in raising the temperature to normal. This is due to the fact that the
temperature of the water of the entire system must be uniformly raised,
because of its continuous passage through the heater. On the other
hand, this uniformity of the temperature of the water prevents sudden
changes in the temperature of the house. Water-heating plants work with
perfect quiet and may be so regulated to suit the outside temperature
that the heat of the water will just supply the amount to suit the
prevailing conditions.

The care required in the management of the boiler is less than that
required in the steam plant because of the fewer appliances necessary
for its safe operation. Another advantage in the use of the hot-water
plant is its adaptability to the temperature conditions during the
chilly weather of early fall and late spring, when a very small amount
of heat is required. At such times the temperature of the radiators is
but a few degrees warmer than the outside air. The amount of attention
necessary for maintaining the proper furnace fire under such conditions
is less then for any other form of heating. The increasing use of the
hot-water plant for heating the average-sized dwelling attests to its
excellence in service.

=The Low-pressure Hot-water System.=--A hot-water system consists of a
heater, in which the water receives its supply of heat, the circulating
pipes for conducting the heated water to and from the radiators that
supply heat to the rooms, and the expansion tank that receives the
excess of water caused when the temperature is raised from normal to
the working degree. In addition to the parts named there are a number
of appliances to be described later, that are required to make the
system complete.

[Illustration: FIG. 32.--Diagram of a simple form of hot-water heating

A hot-water plant of the simplest form is shown in Fig. 32. The
illustration presents each of the features mentioned above, as in a
working plant. The different parts are shown cut across through the
middle, the black portion representing water. Not only does the water
fill the entire system but appears in the expansion tank when the plant
is cold.

Hot-water heaters are quite generally in the form of internally fired
boilers. The fire-box occupies a place inside the boiler and is
surrounded, except at the bottom, by the water space. Commonly, these
boilers are made of cast iron and are constructed in sections, the
same as the steam boiler shown in Fig. 16. Manufacturers sell a single
style for either steam or hot-water heating. The boiler in Fig. 32 is
cylindrical in form. It is made of wrought iron and contains a large
number of vertical tubes through which the heat from the furnace must
pass on its way to the chimney.

As the water is heated it expands and rises to the top of the boiler
because of its decreased weight. Since the water in the radiator is
really a part of the same body of water, the heated portion rises
through the supply pipe to the top of the radiator. As the hot water
rises in the radiator, it displaces an equal amount of cold water,
which enters the boiler at the bottom. This displacement is constant
and produces a circulation that begins as soon as the fire is started
and varies with the difference in temperature between the hot water
leaving the boiler at the top and the cold water entering at the bottom.

As the water in the system is heated and expands, there must be some
provision made to receive the enlarging volume. In this arrangement a
pipe connects the bottom of the boiler with the expansion tank located
at a point above the radiator. Under the conditions represented in
the drawing the water does not circulate through the tank and as a
consequence the water it contains is always cold.

In raising its temperature, water absorbs more heat than any other
fluid and on cooling it gives up an equal amount. As a consequence
it furnishes an excellent vehicle for transmitting the heat of the
furnace to the rooms to be heated. Water, however, is a poor conductor
and receives its heat by coming directly into contact with the hot
surfaces of the furnace, and gives it up by direct contact with the
radiator walls. To transmit heat rapidly and maintain a high radiator
temperature, the circulation of the water in the system must be
the best possible. The connecting pipes between the boiler and the
radiators must be as direct as circumstances will permit and the amount
of radiating surface in each room must be sufficient to easily give up
an ample supply of heat. Even though the furnace is able to furnish a
plentiful supply of heat to warm the house, it cannot be transmitted to
the rooms unless there is sufficient radiating surface. A plant might
prove unsatisfactory either because of a furnace too small to furnish
the necessary heat or from an insufficient amount of radiating surface.
Yet another factor in the design of a plant is that of the conducting
pipes. Both the boiler and the radiators might be in the right
proportion to produce a good plant, but if the distributing pipes are
too small to carry the water required, or the circulation is retarded
by many turns and long runs, the plant may fail to give satisfaction.

Fig. 33 shows a complete hot-water plant adapted to a dwelling. It
is just such a plant as is commonly installed in the average-sized
house but without any of the appliances used for automatic control of
temperature. The regulation of the temperature is made entirely by
hand, in so governing the fire as to provide the required amount of
heat. In the drawing the supply and return pipes may be traced to the
radiators as in the case of the simple plant. The supply pipe from the
top of the boiler branches into two circuits to provide the water for
the two groups of radiators at the right and left side of the house.
To provide any radiator with hot water, a pipe is taken from the main
supply pipe and passing through the radiator it is brought back and
connected with the return pipe which conducts the water back to the

[Illustration: FIG. 33.--The low-pressure hot-water heating system
applied to a small dwelling.]

The expansion tank is located in the bathroom near the ceiling. It is
connected with the circulating system by a single pipe which joins the
supply pipe as it enters the radiator located in the kitchen. Like the
expansion tank in Fig. 31 the water it contains is always cold. It is
provided with a gage-glass which shows the level of the water in the
tank and an overflow pipe which discharges into the bathtub, in case
of an overflow. An overflow pipe must always be provided to take care
of the surplus when the water in the system becomes overheated. This
does not often occur but the provision must be made for the emergency.
The overflow pipe is frequently connected directly with the sewer or
discharged at some convenient place in the basement.

=The High-pressure Hot-water System.=--In the hot-water plant described
the expansion tank is open to the air and the water in the system is
subjected to the pressure of the atmosphere alone. The heat of the
furnace may be sufficiently great to bring the entire volume of water
of the system to the boiling point and cause it to overflow but the
temperature of the water cannot rise much above the boiling point due
to the pressure of the atmosphere.

If the expansion tank is closed, the pressure generated by the
expanding water and the formation of steam will permit the water to
reach a much higher temperature. In the table of temperatures and
pressures of water on page 3, it will be seen that should the pressure
rise to 10 pounds, that is, 10 pounds above the pressure of the
atmosphere, the temperature of the water would be very nearly 240°F.
(239.4°F.). The difference in heating effect in hot-water heating
plants under the two conditions is very marked. In the low-pressure
system the temperature of the radiators cannot be above 212° but the
high-pressure system set for 10 pounds pressure will heat the radiators
to 240°, and a still higher pressure would give a correspondingly
higher temperature. The amount of heat radiated by a hot body is in
proportion to the difference in temperature between the body and
the surrounding air. If we consider the surrounding air at 60° the
difference in amount of heat-radiation capacity of the two radiators
would be as 180 is to 132. The advantage of the high-pressure system
lies in its ability to heat a given space with less radiating surface
than the low-pressure system.

In Fig. 34 is illustrated an application of a simple and efficient
valve arrangement that converts a low-pressure hot-water system into
a high-pressure system without changing in any way the piping or
radiators. The drawing shows the boiler and two radiators connected as
for a low-pressure system, but attached to the end of the pipe as it
enters the expansion tank is a safety valve _B_ and a check valve _A_,
as indicated in the enlarged figure of the valve. The safety valve is
intended to allow the water to escape into the expansion tank when the
pressure in the system reaches a certain point for which the valve is
set. The check valve _A_ permits the water to reënter the system from
the tank whenever the pressure is restored to its normal amount.

[Illustration: FIG. 34.--The high-pressure system of hot-water heating.]

Suppose that such a system is working as a low-pressure plant. The hot
water from the top of the boiler is flowing to the radiators through
the supply pipe and the displaced cooler water is returning to the
bottom of the boiler through the return pipe as in the other plants
described. It is now found that the radiators are not sufficiently
large to heat the rooms to the desired degree except when the furnace
is fired very heavily. It is always poor economy to keep a very hot
fire in any kind of a heater, because a hot fire sends most of its heat
up the chimney. If the radiators could be safely raised in temperature,
they would, of course, give out more heat and as a result the rooms
would be more quickly heated and kept at the required temperature with
less effort by the furnace. The difficulty in this case lies solely in
there being insufficient radiator surface to supply heat as fast as

The increase in radiator temperature is accomplished by the pressure
regulating valve _B_, attached to the end of the pipe as it enters the
expansion tank. The expansion tank with the regulating valve is shown
enlarged at the left of the figure. The valve _B_ is kept closed by
a weight marked _W_, that is intended to hold back a pressure of say
10 pounds to the square inch. A pressure of 10 pounds will require a
temperature of practically 240°F. (see table on page 3). The check
valve _A_ is kept closed by the pressure from the inside of the system.
When the pressure of the water goes above 10 pounds--or the amount of
the weight is intended to hold back--the valve is lifted and an amount
of water escapes through the valve _B_ into the tank, sufficient to
relieve the pressure. Should enough water be forced out of the system
to fill the tank to the top of the overflow pipe, the overflow water is
discharged through this pipe into the sink in the basement.

When the house has become thoroughly warmed, the demand for a high
radiator temperature is reduced, the furnace drafts are closed, the
water in the system cools and as it shrinks the system will not be
completely filled. It is then necessary to take back from the tank the
water that has been forced out by excess pressure. It is here that the
check valve comes into use. So long as there is pressure on the pipes,
this valve is held shut and no water can escape, but as the inside
pressure is released by the cooling there will come a point where the
water in the tank will flow back through the valve _A_ and fill the

This is the type of valve used by the Andrews Heating Co. and
designated a regurgitating valve. In practice it gives excellent
service. The only danger of excessive pressure in the use of this
device is the possibility of the valve becoming stuck to the seat
through disuse. Any possible danger from such an occurrence may be
eliminated by the occasional lifting of the valve by hand.

=Heating-plant Design.=--A heating plant should be designed by a
person of experience. No set of rules has yet been devised that will
meet every condition. Carpenter’s rules given on page 25 serve for hot
water as well as for steam as a means of determining the radiating
surface required for an ordinary building, but the rules do not take
into account the method of construction of the house and the consequent
extra radiation demanded for poorly constructed buildings. In many
cases the designer must rely on experience as a guide where the rules
will not apply. In the case usually encountered, however, the rules
given will meet the conditions.

What was said regarding the size of steam boilers required for
definite amounts of heating surfaces, applies with equal force to
hot-water boilers, because house-heating boilers are commonly used
for either steam or hot-water heating. There are no established rules
for determining the heating capacities of house-heating boilers.
Manufacturers’ ratings are usually low. There are some manufacturers
who make honest ratings for their boilers but they are in the minority.
When the heating capacity of a boiler is not known from experience, the
only safeguard against installing a boiler too small for the radiators
to be heated, is to require a guarantee that the plant will give
satisfaction when in operation and when considered necessary a certain
percentage of the contract price should be withheld until the plant
proves itself by actual trial.

=Overhead System of Hot-water Heating.=--In Fig. 35 is illustrated
another system of high-pressure hot-water heating that corresponds to
the overhead system of steam heating. It differs from the high-pressure
system already described in the method of distribution and in the
radiator connections.

The flow pipe is taken to the attic and there joined to the expansion
tank as a point of distribution. On the expansion tank is a safety
valve set at 10 or more pounds pressure. The flow of the water is all
downward toward the radiators. The circulation through the radiators is
also different from the other plants described. The supply pipe joins
directly to the return pipe and the connections to the radiators are
made at the top and bottom of the same end. The circulation through
the radiators in this case is due to the difference in gravitational
effect between the hot and colder water at the top and bottom of the
radiator. The system requires no air vents on the radiators as all
air that might collect in the system goes up to the expansion tank.
The safety valve on the expansion tank in this case is the common
lever type. The overflow should empty into the sewer and be pitched to
prevent any water being retained in the discharge pipe. If water should
be retained in this pipe and should freeze, the system would become
dangerous, because of the possibility of high pressures from a hot fire.

[Illustration: FIG. 35.--The overhead system of hot-water heating.]

=Expansion Tanks.=--Fig. 36 is a form of expansion tank in common use.
It may be used for either the high-or low-pressure system. The body of
the tank is made of galvanized iron and is made to stand a considerable
amount of pressure. The gage-glass is attached at _B_, and the overflow
at _O_. The pipe _E_ connects the tank with the circulating system and
_D_ connects with the cold-water supply as a convenience for filling
the system with water. The object in placing the stop-cock _D_ near
the expansion tank is to avoid overflowing the system in filling. The
overflow pipe, as stated above, is most conveniently connected with the
sewer, into which the water will run in case of an overflow, but the
other methods shown are commonly used. There should be no valve in this
pipe nor in the pipe _E_.

[Illustration: FIG. 36.--The expansion tank.]

[Illustration: FIG. 37.--When the expansion tank of a hot-water heating
system must be so located that it is apt to freeze, it must be piped as
a radiator.]

The expansion tank must be so located that there will be no danger of
freezing. Should it be necessary to place the tank in the attic or
where freezing is possible, the tank must be so connected as to become
a part of the circulating system. Such an arrangement is shown in Fig.
37. The expansion tank is connected with a supply and return pipe as a
radiator. This arrangement is sometimes used but it is not desirable.
It is wasteful of heat and there is always a possibility of freezing
in case the fire in the furnace is extinguished a sufficient time to
allow the water to grow cold.

Any possibility of danger from excessive pressures in either the
low-pressure or the high-pressure system must originate in the
expansion tank. It is, therefore, desired to again mention the
possible causes of danger. Any closed-tank system is liable to become
overheated. The expansive force of water is irresistible and unless
some means is taken to prevent excessive pressure some part of the
apparatus is apt to burst. _No closed-tank system should be used
without a safety valve._

The low-pressure or open-tank system requires no safety appliances. So
long as there is open communication between the tank and the boiler the
pressure cannot rise but slightly above that of the atmosphere. There
is only one cause that will lead to high pressure in such a system. If
the pipe connecting the expansion tank is stopped an excessive pressure
might generate. There is little or no danger of this happening.

In the closed-tank system the expansion tank should be of greater
capacity than for the open-tank system. Its size is commonly about
one-ninth of the volume of water used. The larger tank is necessary
to prevent too rapid rise of pressure as the temperature of the water
rises. The air in the tank acts as a cushion against which the pressure
of the expanding water is exerted.

The extended use of hot-water heating has led to the invention of many
appliances for the improvement of the circulation and heating effects.
Pulsation valves are used for retaining the water in the boiler until
a definite pressure has been attained that will lift the valve long
enough to dissipate the pressure. Many of these systems possess merit
and some of them are great improvements over the simple plant.

=Radiator Connection.=--The method of connecting the radiators to
the distributing pipes depends entirely on local conditions. In a
well-balanced system any of the methods shown in Figs. 38, 39 or 40
might be used with good heating effects. The method of attaching the
supply pipe to the radiator is, however, an important factor in case
of accumulation of air. In Fig. 41 is shown the form of connection
most commonly used. The drawing is intended to represent a cast-iron
radiator with the valve at _D_, and the air vent at _B_. Should air
collect in the radiator it will rise to the top and displace the water.
The water will continue to circulate and heat as much of the radiator
as is in contact with the water, but that part not in contact will
receive no heat from the water and will, therefore, fail to fulfill its
function. As soon as the air vent is opened the air will escape and
allow the water to entirely fill the space.

[Illustration: FIG. 38. FIG. 39. FIG. 40.

FIGS. 38 TO 40.--Various methods of attaching the supply and return
pipes to hot-water radiators.]

[Illustration: FIG. 41.--The effect of accumulation of air in a
hot-water radiator with bottom connections.]

[Illustration: FIG. 42.--With this method of connections, if the
air collects sufficiently to force the water down to the level L,
circulation will stop.]

In Fig. 42 a much different condition exists, when air accumulates. In
this mode of connection the water enters through the valve _V_, and
escapes at the bottom of the opposite end. When air fills the radiator
to the line _L_, the circulation is stopped and the radiator will grow

The position of the valve on these radiators is of little consequence.
The valve is intended merely to interrupt the flow of the water and may
occupy a place on either end of the radiator with the same result.

=Hot-water Radiators.=--Radiators for hot-water heating are most
commonly of cast iron and in appearance are the same as those used for
steam heating. The only difference in the two forms is in the openings
between the sections. Those intended for steam have an opening at the
bottom joining the sections; while those for hot water have openings at
both top and bottom to permit circulation of the water.

[Illustration: FIG. 43.--The hot-water radiator valve.]

[Illustration: FIG. 43_a_.--Details of construction of the hot-water
radiator valve.]

=Hot-water Radiator Valves.=--Valves for hot-water radiators differ
materially from those used on steam radiators. Figs. 43 and 43a show
the outside appearance and the mechanical arrangement of the parts
of the Ohio hot-water valve. The part _A_ in Fig. 43_a_ is a hollow
brass cylinder attached to the valve-stem, one side of which has been
removed. When it is desired to shut off the supply of heat the handle
of the valve is given one-quarter turn and the part _A_ covers the
opening to the inlet pipe. The supply of water being shut off, the
radiator gradually cools. When the valve is closed a small amount of
water is admitted to the radiator through a 1/8-inch hole in the piece
_A_ to prevent the possibility of freezing.

=Air Vents.=--In the use of the systems of hot-water heating described,
every radiator must be supplied with an air vent of some kind to take
away the trapped air which accumulates through use. Any kind of a valve
will serve as a vent for hand regulation and generally such a cock as
is shown in Fig. 10 is employed.

=Automatic Hot-water Air Vents.=--It is sometimes desired to use
automatic air vents on hot-water radiators. For such work a vent is
used that remains closed as long as water is present and will open when
the water is displaced by the accumulating air, but will again close
when the air is discharged. In such vents the valve is controlled by
a float, the buoyancy of the float when surrounded by water serving
to keep the valve closed. These vents are not so positive in their
action as automatic air vents for steam. The change in temperature
which controls the steam vent does not take place with hot water. The
automatic hot-water vents are not perfectly reliable. They may work
with entire satisfaction for a long time and then fail from very slight
cause. The failure of a hot-water vent is generally discovered by
finding a pool of water on the floor or a wet spot on the ceiling or
wall of the floor below.

[Illustration: FIG. 44.--Automatic air vent for hot-water radiators.]

One type of the automatic hot-water vent that has proven quite
successful is shown in Fig. 44. The threaded lug is screwed into the
radiator at the proper point. As the water enters the radiator the air
is discharged through the vent, escaping at the opening _C_. When the
water has risen to a sufficient height it enters the openings _G_ and
_H_ until enough is present to raise the float _A_. The pointed stem
attached closed the hole _C_ with sufficient force to make an air-tight
joint. The float _A_ is a very light copper cylinder. Its buoyancy
supplies the force to close the vent and its weight opens the vent when
the water is displaced by air. It will be readily seen that very slight
cause might prevent the performance of its duty.



Of the methods of heating dwellings other than by stoves, that of the
hot-air furnace is the most common. Of the various modes of furnace
heating it is the least expensive in first cost and most rapid in
effect. In the use of steam heat, the water in the boiler must be
vaporized before its heat is available. With hot-water heating, the
whole mass of water in the entire system must be raised considerably in
temperature before its heat can affect the temperature of the rooms,
and consequently in first effect it is very slow. In the use of the
hot-air furnace the heat from the register begins to warm the rooms
when the fire is started.

Hot-air furnaces are made by manufacturing companies in a great variety
of styles and forms to suit purposes of every kind. In practice the
furnace is built in sizes, to heat a definite amount of cubical space.
The maker designs a furnace to heat a certain number of cubic feet of
space contained in a building. It must be sufficiently large to keep
the temperature at 70°F. on the coldest nights of winter when the
wind is blowing a gale. It is evident that with the variable factors
entering the problem, the designer must be a person of experience in
order that the furnace meet the requirements.

The following table taken from a manufacturer’s catalogue shows the
method of adapting the product of the maker to any size of dwelling.
The volume of the house is calculated in cubic feet and from this
result the size of furnace most nearly suited is selected from the

  Furnace number          |    1   |    2   |    3   |    4   |    5
  Weight without casing,  |    984 |  1,111 |  1,340 |  1,531 |  1,934
  lb.                              |        |        |        |
  Estimated capacities in |  8,000 | 12,000 | 20,000 | 35,000 | 60,000
  cubic feet              |   to   |   to   |   to   |   to   |   to
                          | 12,000 | 20,000 | 35,000 | 60,000 |100,000
  Capacity in number of   |        |        |        |        |
  rooms of ordinary size  | 3 to 5 | 5 to 7 | 7 to 9 |9 to 12 |12 to 15
  in residence heating    |        |        |        |        |


[Illustration: FIG. 45.--Interior view of a hot-air furnace.]

The furnace, in general construction, consists of a cast-iron fire-box
with its heating surfaces, through which the flames and heated gases
from the fire pass, on the way to the chimney; these with the passages
and heating surfaces for heating the air compose the essential
features. Fig. 45 shows such a furnace with the sides broken away to
show the internal construction. The flames and gases from the fire-box
_F_ circulate through the cast-iron drum _D_ and are discharged at _C_
to the chimney. The drum _D_ is made in such form that it presents to
the heat from the fire a large amount of heating surface and at the
same time offers as little opposition as possible to the furnace draft.
The air to be heated enters the furnace through the cold air duct at
the bottom, and after circulating through the drum, passes out at
the openings _R_ to the conducting pipes. The cast-iron box _W_ is a
water tank that should be attached to every hot-air furnace. The water
contained in the tank is for humidifying the air as it passes through
the furnace. In this furnace the outside casing is of sheet iron,
reinforced with wrought-iron flanges. The front, which contains the
doors of the fire-box, ash-pit, etc., are of cast iron of ornamented

As the air to be heated passes through the furnace it receives part of
its warmth by radiation but most of it is absorbed by coming directly
into contact with the heating surfaces. Since air is a poor conductor
of heat its temperature is raised very slowly; it should, therefore,
be kept in contact with the heating surfaces as long as possible to
insure an economical furnace. In common practice the ratio of heating
surface to grate surface average 35 to 1; that is, for each square foot
of grate surface there is 35 square feet of heating surface to warm the
passing air. Should this ratio be increased to 50 to 1 the efficiency
of the furnace would be much improved.

If the ratio of heating surface to the grate surface is too small for
its requirements, the temperature of the air-heating surfaces must be
very high to provide the desired amount of heat. Under such a condition
the efficiency of the furnace would be low, since in all cases where
rapid combustion is required the available amount of heat per pound of
coal consumed is low. With a large amount of heating surface, the air
remains in contact with the hot surface a relatively longer period and
the desired temperature is reached with the expenditure of a smaller
amount of fuel. A momentary exposure of the air to a red-hot surface
is far less effective than a prolonged contact with a surface having
only a moderate temperature. Time is an element of great importance
in heating air. In considering the relative merits of two furnaces
with the same amount of grate surface, that with the larger amount of
heating surface will evidently be the most efficient.

The supply of heat comes primarily from the burning coal on the furnace
grate. The grate surface should be large enough in area to permit the
required quantity of heat to be generated by the burning fuel with
a moderate fire. If the grate surface is too small for the required
purpose, a hot fire will be necessary, when the normal amount of heat
is demanded by the house. During extremely cold weather, particularly
when accompanied by high wind, the extra heat demanded to keep the
house at the desired temperature makes necessary the use of an amount
of fuel that cannot be burned on the grate unless the fire is forced.
Hot fires can be kept up only at the expense of a large amount of heat,
and the resultant efficiency of the furnace is reduced.

High furnace temperatures are always attended by a large loss of heat.
The vastly greater quantity of air necessary to create the combustion,
the high temperature of the chimney gases and the increased velocity of
the heated gases through the furnace, all tend to increase the amount
of heat that is sent up the chimney, and to decrease the percentage
of heat that is delivered by the furnace. In order to heat the house
economically the furnace must be large enough to easily generate the
required amount of heat demanded in the most severe weather.

=Furnace-gas Leaks.=--The presence of furnace gas in the atmosphere of
a house is not only annoying but may be a source of danger. Gas leaks
are commonly due to the imperfect union of the various parts of which
the furnace is composed.

Cast-iron furnaces are constructed in sections that are assembled to
form a complete plant. In assembling, the various parts of contact must
be carefully joined to prevent the gases in the fire-box from escaping
into the air-heating space. In the manufacture of cast-iron furnaces it
is practically impossible to form gas-tight joints by the contact of
the metal alone. In the erection of the furnace all doubtful joints are
filled with stove putty. Furnaces of good design require the use of the
least amount of this material.

Stove putty is composed of finely divided graphitic carbon that is
made into a paste suitable for filling all imperfect joints. When
the putty hardens it withstands the heat to which it is subjected,
without shrinking. In the course of time, however, the putty may be
displaced and leave openings through which the furnace gases may leak
into heating space and thus enter the house. Leaks of the kind may be
stopped by renewing the putty which may be obtained from any dealer in

=Location of the Furnace.=--The location of the furnace will generally
be governed by the exposure of the house and the location of the
chimney. In all exposed rooms on the windward side of the house the
temperature will be lower and the air pressure higher than in other
parts of the house. The increase in atmospheric pressure makes it
necessary to supply to such rooms the hottest air practicable. The
conducting pipes, therefore, should be most directly connected with the
furnace and with the least run of horizontal pipe. The proper place for
the furnace is as near as possible the coldest place of the house.

It is a common practice to place registers near the inner corner of
the room, in order to economize in conducting pipe, in horizontal
runs. A small amount of economy in first cost is thus secured but the
efficiency of the apparatus is sacrificed.

The greatest objection to placing the registers and conducting pipes in
the outer walls of buildings is that of loss of heat, due to exposure
to the outside cold and the resulting loss in circulation. Losses of
this kind may be prevented by covering the ducts with the necessary
non-conducting material. The registers should occupy a place in the
room nearest the entering cold air.

[Illustration: FIG. 46.--Method of conducting warm air from the furnace
to the registers.]

=Flues.=--It is customary to place the conducting pipes for the first
floor in such a way as to use only the shortest connections. The flues
used for the second floor produce, as in a chimney, a greater velocity
of flow to the air and as a consequence larger _horizontal_ pipes are
used at the furnace. All horizontal pipes should have upward slant, as
much as the basement will permit.

The velocity of the air in the conducting flues will depend on two
factors: the height of the flue, and the temperature of the air. To
prevent the loss of the temperature of the air, the flue should be
covered with at least two layers of asbestus paper bound with wire.
Wall flues are commonly flattened and occupy a place in the wall
between the studding. Each flue should have a damper at the furnace,
that will permit the heat to be shut off from any part of the house.

Rules for proportioning of registers and conducting flues to suit
rooms of various sizes are entirely empirical. The sizes of registers
and flues found satisfactory in practice is generally a guide for the
designer. The following table is taken from a manufacturer’s catalogue
and gives a list of sizes that have proven satisfactory under a great
variety of conditions and may be taken as good practice:

                     FIRST FLOOR
   Sizes of  | Diameter of |   Size of  | Height of
  registers  |   pipes     |    rooms   | ceilings
  in inches  | in inches   |   in feet  |  in feet
   12 by 15  |     12      |  18 by 20  |    11
   10 by 14  |     10      |  15 by 15  |    10
    9 by 12  |      9      |  14 by 15  |     9
    8 by 12  |      9      |  13 by 13  |     9
                    SECOND FLOOR
   10 by 14  |     10      |  18 by 20  |    10
    9 by 12  |      9      |  16 by 16  |     9
    8 by 12  |      8      |  13 by 13  |     8
    8 by 10  |      7      |  12 by 12  |     8

The furnace is not only a means of heating the house but may be a means
of ventilation as well; to this end it is desirable to arrange the air
supply of the furnace to connect with the outside air. This arrangement
assures a supply of oxygen even though no special means is arranged for
discharging the vitiated air from the rooms.

[Illustration: FIG. 47.--Interior construction of a combination
hot-water and hot-air furnace.]

=Combination Hot-air and Hot-water Heater.=--In the case of large
houses heated by hot air it is sometimes better to use two or more
furnaces than to attempt to carry the heat long distances in the
customary pipes. Where heat is required in rooms located at a distance
more than 30 feet, it is advisable to use a combination hot-air and
hot-water heater, the distant rooms being heated by hot-water radiators.

A furnace arranged for such a combination is shown in Fig. 47. This
furnace contains, first, the essential features of a hot-air furnace;
next, it includes a hot-water plant. The fire-box and air-heating
surfaces are easily recognized. The arrows show the course of the air
entering at the bottom of the furnace, which after being heated by
passing over the heating surfaces, escapes at the openings marked _warm
air_, to the distributing pipes.

[Illustration: FIG. 48.--The hot-air furnace as it appears in the

Inside the air-heating surfaces are three hollow cast-iron pieces _W_,
that form a part of the walls of the fire-box. These pieces, with their
connecting pipes, form the water-heating part of the furnace, which
supplies the hot water for the radiators. The pieces _W_, with the
connecting pipes and radiators, form an independent heating plant, with
a fire-box in common with the hot-air furnace.

The returning water from the radiators enters the heating surfaces _W_,
through the pipe marked _return pipe_. The heated water is discharged
from the heaters into that marked _flow pipe_ which conducts it to the
radiators. Such a furnace is, therefore, two independent systems, one
for hot air and the other for hot water, but with a single fire-box.
This furnace, like the simple hot-air furnace, is rated, first in the
amount of space it will heat with hot air and in addition, by the
number of square feet of hot-water radiating surface that will be kept
hot by the hot-water heater.

In Fig. 48 is shown the location of the furnace in a cottage with the
conducting pipes to the various rooms. The registers in the first floor
are generally set in the floor but if desired they may be placed in the
walls. Those on the second floor are placed in the walls because of
convenience. The conducting pipes pass through the partitions between
the studding.

[Illustration: FIG. 49.--Details of air ducts and damper regulator used
with the hot-air furnace.]

In all well-arranged hot-air heating plants provision is made so that
the air for heating may be taken from the outside. It does not follow
that the supply of fresh air should always come from outdoors; there
are times during extremely cold weather, accompanied by high winds,
when ventilation is ample without the outside source of supply. Since
it is never desirable to take the air supply from the basement, such
an arrangement as is shown in Fig. 49, or a modification of the same
plan is commonly employed. The duct _A_ from the outside and _B_ from
the rooms above connect with the air supply for the furnaces. A damper
_C_ arranged to move on a hinge, is so placed as to admit the air from
either source as desired. The damper may be placed so as to take part
or all of the air from the outside by adjusting the handle at the
proper place.



The method used for regulating the temperature of a house will depend
on its size, the conditions under which it is to be used and the method
of heating. In small houses the temperature may be satisfactorily
governed entirely by hand, that is, the furnace drafts may be changed
by hand to suit the varying conditions of temperature. A more
satisfactory method is that of thermostatic regulation, in which a
thermostatic governor and a motor automatically control the furnace
dampers so as to keep a constant temperature at one point, generally
the living room. Where hot-water or steam heating plants are used,
another device is frequently employed to keep the temperature of the
heat supply at a constant degree. This is known as the automatic damper
regulator. The damper regulator is one of the boiler accessories which
so governs the drafts of the furnace as to keep a constant water
temperature in the hot-water heater or a constant steam pressure in the
steam boiler.

In some cases both the damper regulator and the thermostat are used as
a more complete means of temperature control.

=Hand Regulation.=--As a means of changing the dampers of the
furnace from the floor above, to suit the prevailing conditions, the
arrangement shown in Fig. 49 does away with the necessity of a journey
to the basement, to remedy each change of temperature.

A plate is fastened to the wall at any convenient place, to which the
end of a chain is attached as shown in the figure. This connects with a
second chain, the ends of which are fastened, one to the direct draft
or ash-pit damper _F_, and the other to the check draft _E_, in the
chimney. As the furnace appears in the drawing, the direct draft is
closed and the check draft is open. By changing the ring from _G_ to
_H_, the movement of the chain opens _F_, and closes _E_, admitting
air to the furnace. When the temperature of the room is raised
sufficiently, the drafts are restored to their original position by
replacing the ring at _G_. Sometimes one or more intermediate points
are made on the plate between _G_ and _H_, which permits both drafts
to be kept partly open and fewer changes are required to keep the
temperature approximately normal.

[Illustration: FIG. 50.--Cross-section of damper regulator for steam

[Illustration: FIG. 51.--Steam boiler for house heating, with the
damper regulator, in place, attached to the dampers.]

=Damper Regulator for Steam Boiler.=--The damper regulator used on
a steam boiler is a simple device that automatically controls the
draft dampers by reason of the changing pressures of the steam. The
object of the damper regulator is to prevent the generation of steam
in the boiler beyond a certain pressure at which the valve is set.
This point is usually 3 or 4 pounds below the pressure at which the
safety valve would act. If in proper working order the damper regulator
will so control the dampers that the boiler will always contain a
supply of steam, but the pressure will not reach a point requiring
the action of the safety valve. Fig. 51 illustrates its connections
with the furnace dampers. In Fig. 18 the regulator appears at _D_. In
external appearance and in operation of the dampers, it is the same
as the regulator for a hot-water boiler but its internal construction
is simpler. Fig. 50 shows its construction. It is attached to the
steam space of the boiler at _E_. The steam pressure acts directly on
the flexible metallic diaphragm _B_. As the pressure of the steam
approaches the desired amount the diaphragm is raised and with it the
lever _V_. A chain _D_, attached to the end of the lever, opens the
check draft, and another at _C_ closes the draft damper. When the steam
pressure falls, the diaphragm lowers the lever and the dampers are
restored to their original position. The same movements are repeated
with each rise and fall of the steam pressure.

[Illustration: FIG. 52.--Damper regulator for hot-water boiler.]

=Damper Regulators for Hot-water Furnaces.=--The damper regulator for
a hot-water boiler automatically controls the dampers of the furnace
so as to keep the water of the boiler approximately at a constant
temperature. The regulator is shown in Fig. 52. The ends of the lever
are connected to the direct-draft and check-draft dampers, as in the
case of the damper regulator for the steam plant. A cross-section of
the working parts shows the details of construction. The lever _d_
is operated by a diaphragm _g_, which tightly covers a brass bowl,
containing a mixture of alcohol and water, of such proportions as will
produce a vapor pressure at the desired temperature, say 200°. The
hot water from the boiler passes through the valve, entering at _a_
and leaving at _b_. When the water reaches the desired temperature,
the contained liquid vaporizes and a pressure is produced that is
sufficient to lift the diaphragm and the lever. The chain attached to
the right-hand end closes the direct-draft damper; at the same time the
other end of the lever opens the check draft, and the supply of air to
the furnace fire is entirely cut off. As soon as the water has cooled
sufficiently, the vapor pressure in the bowl is reduced, allowing
the weight _W_ to depress the diaphragm and the lever is restored to
its first position. The weight _W_ is for adjusting the valve to the
desired temperature. The plug _f_ tightly closes the orifice through
which the liquid is introduced into the bowl.

The object of the damper regulator on a hot-water boiler is to govern
the fire of the furnace so as to keep the water in the boiler at the
desired temperature. In case there is a demand for heat at any part of
the house, a supply of hot water will always be on hand. It has nothing
to do with the regulation of the temperature of the house. The control
of the house temperature is the office of the _thermostat_.

=The thermostat= is a mechanical device for automatically regulating
temperature. It may be arranged to operate the valve of a single
radiator or register and so control the temperature of a room, or as
commonly used in the average dwelling, the controller may be placed
to govern the temperature of the living room and in so doing keep the
furnace in condition to satisfactorily heat the remainder of the house.

Thermostats are made in a variety of forms by different manufacturers
but they may be divided into two general classes: the electric, and
the pneumatic types. The electric thermostat depends on an electric
current as a means of controlling the action of the motor which in turn
operates the furnace dampers so as to maintain a constant heat supply.
The pneumatic thermostat regulates the supply of heat by means of
pneumatic valves. It will be considered later in discussing mechanical
ventilation. This type of temperature regulation is particularly
adapted to large buildings.

Fig. 53 illustrates one style of electric thermostat that is very
generally used for temperature regulation in the average dwelling. It
consists of three distinct parts--the controller, the electric battery
and the motor. In the drawing the motor is shown connected with a
steam valve, such as may be used for furnishing steam for a series of
radiators. It may with equal facility be attached to the dampers of a
furnace or other heating apparatus.

The controller occupies a place on the wall of the room to be heated
and makes electric connections between the battery and the motor.
Whenever the temperature varies from the required degree, a change of
electric contact in the controller starts the motor, and the radiator
valve or the furnace drafts are opened or closed as occasion requires.

The controller appears in Fig. 54 as commonly seen in use. The
upper part carries a thermometer and the pointer _A_ indicates the
temperature to be maintained in the room. The middle division indicates
70°F. Each division to the right of the middle point raises the
temperature 5°. Each division to the left lowers the temperature a like

In addition to the ordinary type this controller is furnished with
a time attachment by means of which the controller may permit the
temperature of the room to fall to any desired degree at night and
raise it again in the morning at the time for which it is set.

This is accomplished by a little alarm clock shown at the bottom of the
controller in Fig. 54. The indicator _B_ is arranged to correspond with
the indicator _A_; the middle point representing 70°F. To set the time
attachment, the alarm is wound and set as in any alarm clock, 1/2 hour
earlier than the desired time for rising. The indicator _B_ is set for
the day temperature and _A_ is set for the temperature desired during
the night. At the appointed time the alarm moves the indicator _A_ to
the desired point for the day and the controller raises the temperature

Fig. 55 shows the mechanism that is exposed to view when the cover
of the controller is removed. The bent strip _C_ is the part that is
influenced by the change of temperature. It is made of two thin strips
of metal, one of brass and the other of steel. The two strips are
soldered firmly together. Any change in temperature will affect the
strip and cause it to bend and touch the contact point--_K_ or _J_. The
bending of the strip is due to the unequal expansion of the brass and
steel due to the change of temperature. Brass expands 2.4 times as much
as steel with the same change of temperature. The amount of bending
is sufficient to make an appreciable movement in a small fraction of
a degree change. The brass part of _C_ is on the left and since it
expands the greater amount, a rising temperature causes _C_ to come
into contact with the point _J_. When this happens the motor is started
and makes one-half cycle. In so doing it shuts off the air supply
of the furnace, opens the check draft and at the same time the motor
changes the electric contact from _J_ to _K_. When the temperature
begins to fall, the brass contracts in the same ratio to the steel as
it expands during the rising temperature and as a consequence the bar
bends to the left. When the strip touches the point _K_ the motor again
makes one-half circle, admitting air once more to the furnace, closes
the check draft and shifts the electric contact back to _K_. When
properly started the thermostat will regulate the temperature within a
degree of temperature.

=The Thermostat Motor.=--The thermostat motor automatically opens
and closes the furnace dampers or the valve that admits steam to the
radiators as heat is demanded by the controller.

The motor, as shown in Fig. 53, consists of a system of gears and a
brake _S_, which regulates the speed, a cam _M_, and armature _I_, for
starting and stopping the motor, and the electromagnet _H-H_ which
operates the bar _I_. Two lever arms _L_, one in front and the other
at the back of the motor furnish means for attachment to the valve or
furnace dampers. An emergency switch at _D_ is shown in detail in Fig.
56. The battery _B_ furnishes the current which energizes the magnets
and an iron weight supplies the motive power for the motor.

The description of the operation of the motor applies to the steam
valve shown in Fig. 53. The same motor might be used for opening and
closing of the dampers of the furnace in any kind of heat supply. The
method of communicating the motion of the motor arms to the dampers of
the furnace will be described later. The connections with the furnace
drafts are shown in Figs. 3, 6, 8, 34, etc.

Suppose that the valve for admitting steam to the radiators, as
that in Fig. 53, is closed and that the temperature of the house is
falling. The strip _C_ of the thermostat controller is moving toward
_J_. When contact is made, the current from the battery _B_ energizes
the magnets _H-H_ and the bar _I_ is lifted. As the bar _I_ is raised
the catch _J_ is released and permits the motor to start. The bar _I_
is held suspended by the cam _M_ until the arm _L_ has made one-half
revolution, when the lug _K_ drops into the depression in the cam made
to receive it and the catch _J_ engages with the brake and stops the

[Illustration: FIG. 53.--Thermostat complete with the regulator,
battery and motor, attached to a steam supply valve.]

During this movement the arm _L_ has lifted the valve arm _N_ and the
valve admits steam to the radiators, at the same time the contact _M_
has been shifted from the right-hand contact to the left, and the
electric circuit is ready to be made in the controller at the point
_K_. When the temperature has fallen a sufficient amount the controller
bar _C_ will make contact at _K_ and the motor will again make a half
cycle, changing the valve back to its original position. This process
will be kept up so long as the motor is wound and there is sufficient
fuel in the furnace to raise the temperature.

Fig. 55 shows the method of connecting the electric wires from the
battery to the controller. A three-wire cable connects the battery, and
makes contacts as indicated at _H_, _K_ and _J_. The wires are shown
attached to the motor as in Fig. 55. A wire is taken from either pole
of the battery and attached to one of the ends of the magnet coil.
Passing through the magnet the wire is attached to the frame of the
motor. This makes the cam _M_ a part of the electric circuit. The other
two wires are attached to the brass strips on each side of the arm _L_.
The strips are insulated from the frame. The electric circuit through
the magnet is made alternately by contact with the strips at right and
left of the arm _L_.

[Illustration: FIG. 54.--Thermostatic regulator with clock attachment
for control of day and night temperature.]

In case the motor, through neglect, runs down, a safety switch at _D_
(Fig. 53) disconnects the battery and keeps it from being discharged.
This switch is shown in detail in Fig. 56. When the weight has reached
its limit, the piece _C_ on the chain comes into contact with _D_ and
lifting it out of contact, breaks the circuit. When the motor is again
wound, _C_ engages with _E_ and restores the contact. The switch is so
arranged that when open, the valve will always be closed.

[Illustration: FIG. 54_A_.--Showing the clock attachments to the
thermostatic regulator.]

[Illustration: FIG. 55.--Mechanism of the thermostatic regulator.]

=Combined Thermostat and Damper Regulator.=--It is evident that, in
heating a house by steam, the _damper regulator_ governs only the
steam pressure of the boiler. In the use of a thermostat alone, the
regulation is that of the temperature of the rooms only, and has
nothing to do with the steam pressure. As an example: Suppose that in
cold weather the house is cold and that the gage of the steam boiler
shows no pressure. The desire is to get up steam as soon as possible.
In so doing a hot fire is made with a large amount of fuel. As soon
as the steam begins to form, the pressure rises rapidly. When the
radiators have become hot and the steam is no longer taken away as
fast as it is formed, the pressure of the steam in the boiler keeps on
rising. The thermostat will not close the furnace dampers until the
temperature of the rooms is normal. This may require so great a length
of time as to produce a great excess of steam that cannot be used at
the time and the pressure will be relieved by the safety valve. This
may not be dangerous but it is disagreeable. To prevent the safety
valve from blowing except in case of emergency, a combined thermostat
and draft regulator is used. In such a combination, the draft
regulator closes the draft as soon as the pressure reaches the desired
point, after which the thermostat does the regulating according to suit
the temperature of the house.

In Fig. 2 is shown such a combination attached to a boiler. The cord
from the regulator, instead of extending directly to the direct-draft
damper, passes over the pulley _P_ and connects to the thermostat cord.
The regulator may now close the damper to suit the steam pressure,
but after the temperature in the rooms is normal, the amount of heat
necessary to maintain the desired degree is regulated entirely by
the thermostat which opens and closes the dampers regardless of the
position of the damper regulator.

If occasion should require but a very slight amount of steam to keep
the house at the desired temperature, the thermostat will govern
the drafts aright. If the steam pressure is in danger of becoming
excessive, the damper regulator will govern the drafts.

[Illustration: FIG. 56.--Automatic switch which opens the battery
circuit when the thermostat motor weight, reaches its limit.]

=Thermostat-motor Connections.=--The arrangement of cords and pulleys
used for attaching the thermostat motor to the furnace dampers will
depend very much on local conditions. The motor can be placed in
any convenient position so that the connecting cords will act most
directly. The motor opens and closes the direct draft and check draft
in accordance with the demand for heat. The connections for all kinds
of furnaces are made in much the same manner. The pulleys supplied
with the motor are placed to work as freely, and the cords to pull as
directly as possible.

In Fig. 57 the motor is connected with a hot-air furnace. The cord
_D_ is attached to the front arm of the motor and connects with the
direct-draft damper _F_. The cord _C_ connects the rear arm of the
motor with the check-draft damper at _E_. In the position of the
dampers shown, the direct-draft damper is closed and the air is
entering the chimney through the check draft _E_. While this damper is
open there is very little induced draft to supply the fire with air
that might leak through the crevices around the ash-pit door, but the
gases from the furnace are completely carried away to the chimney by
the air entering at _E_.

[Illustration: FIG. 57.--Thermostat motor connected with the dampers of
a hot-air furnace.]

In Figs. 3, 6, 8, 34, etc., the same motor is connected with the
furnaces of various other systems of heating. The object is the same
in all; when less heat is required, the air supply is cut off and the
furnace fire subsides; when more heat is demanded the air is again
admitted to produce greater combustion. The check draft is an important
feature as it checks the flow of air through the furnace regardless
of the position of the direct-draft damper. Even should the direct
draft be left open, the check draft when open would destroy in a great
measure the supply of air entering the furnace.



The following instructions on the care and management of steam and
hot-water heating plants is printed with permission of the American
Radiator Co. They were prepared as a guide to the successful operation
of the Ideal heating plants but apply with equal force to other plants
of a similar character.

=General Advice.=--No set rules can be given for caring for every
boiler alike--chimney flues are not alike--some have strong draft,
some are average and some are weak. There is much more difference in
the heat-making qualities of coal than is commonly known, and it is
important that the right size coal for the draft be used. These rules
apply to most all fuels. A little trying of this way or that way of
leaving the dampers (when regulators are not used) often discovers the
better way. It is well to vary from the rules a little if any of them
do not seem to bring about the best results.

With good, average chimney flue draft and the right kind of fuel, these
rules will govern the large majority of cases.

=The Economy of Good Draft.=--In many cases a boiler with sluggish
draft will burn more coal than a boiler with good draft. In the first
case the fuel may be said to “rot”--in lacking air supply the gases
pass off unburned. The “nagging” which a boiler has to take under these
conditions increases the waste of fuel. A boiler under sharp, strong
draft maintains a clear intense fire and burns the gases--getting the
larger amount of heat from the coal.

=General Firing Rules.=--

1. Put but little coal on a low fire.

2. When adding coal to the boiler, open the smoke-pipe damper (inside
the smoke pipe) and close the cold-air check damper. This will make a
draft through the feed doorway inward and prevent the escape of dust or
gas into the cellar when the feed door is open to take fuel. Put these
parts back to their regular places after feeding.

3. When it can be done, in feeding a large amount of coal (as for
night) leave a part of the fire or flame exposed, so that the gases may
be burned as they arise.

4. When a regulator is not used, learn to use the dampers correctly
and according to the force of the chimney draft. Learn to use cold-air
check damper. Often, when closing, the ash-pit draft damper does not
check the fire enough; opening the cold-air check damper will check it
about right. Increasing or lessening the pressure of a steam boiler
must be done by changing the weight on the regulator bar.

5. Carry a deep fire or a high fire; let the live coals come up to the
feed door--even in mild weather when from 4 to 6 inches of ashes stand
on the grate.

[Illustration: FIG. 57_a_.--Indicates the general condition of the
furnace fire during very cold weather. The fuel should fill the
fire-pot to _C_. The ashes should not be allowed to accumulate beyond
_B_, on the grate. There should be no more ashes than appear at _H_, in
the ashpit.]

6. In severe weather give the heater the most careful attention the
last thing at night.

7. Do not overshake or poke the fire in mild weather; once in a while
shake enough to give place for a little more fuel.

8. Do not let ashes bank up under the grate in ash-pit. Grate bars are
very hardy, but it is possible to warp them with carelessness. Taking
up the ashes once a day is the best rule, even if but little has fallen
into the pit.

9. Keep the boiler surfaces and flues clean; a crust of soot 1/4 inch
in thickness causes the boiler to require half as much more fuel than
when the surfaces are clean.

10. If convenient, have a water hose to spray the ashes when cleaning
out the pit.

11. Attend the boiler from two to four times per day. In mild weather,
running with a checked fire, morning and night is usually often enough.
In severe weather, once in early morning, again at mid-day, again at
five or six o’clock and finally thorough attention at from nine to
eleven o’clock in the evening.

12. If, through burning poor coal, the fire pot gets full of ashes,
or slate and clinkers massed together, the quickest way to get a good
active fire is to dump the grate and then build a new fire--from the
kindling up.

13. If a _hard clinker_ lodges between the grate bars, do not force the
shaking, but first dislodge the mass with a poker or slicing bar. Then
the grate will operate without damage.

=Weather and Time of Day.=--In _severe weather_ keep the fire pot full
of coal, and run the heater by the dampers or regulator (if one is
used). Thoroughly clean the grate twice a day. Let the top of the fire
in front be level with the feed door sill. Bank up the coal higher to
the rear.

In _moderate weather_ there should be from 2 to 6 inches of ashes
between the live coal and the grate. As the weather grows colder keep
the grate and the fire pot a little cleaner--sometimes it helps to run
the poker or slicing bar over it through the clinker door. With some
fuels this is never necessary.

=Night Firing.=--In very _cold weather_, when the house should be kept
warm all night, clean the grate well at a late hour--the last thing.
Clear the bottom of the fire pot of all ashes and clinkers so that the
grate is covered with clear-burning, red-hot coals, then fill the pot
full of fuel. If possible, leave some of the flame exposed to burn the
gases. Leave the drafts on long enough to burn off some of the gas,
then check the heater for the night. Thus there is plenty of coal
to burn during the night and some on which to commence early in the
morning. Some drafts do not make it necessary to leave the dampers on
to burn off the gas after feeding.

With the ash-pit draft damper closed and the cold-air check damper
open at night, but part of the coal is burned and there is much of it
not burned in the morning. So, by reversing the dampers in the early
morning the fire starts up quickly and often the house may be well
warmed before any coal is put into the fire pot.

Some boilers are run the other way--a very poor way. If the grate is
cleared off in very cold weather and coal added at five or six o’clock
in the afternoon, by eleven o’clock at night nearly one-half of the
coal is burned and the grate is covered over with a mass of ashes and
clinkers. With little coal remaining, to shake the grate will quite
likely put out the remaining fire; to put fresh coal on a low fire
reduces further its declining temperature. The result is a cold house
that will grow colder until a new fire is started.

Often in cold weather with this poor way of night firing, it takes one
or more hours of forced firing to warm the house in the morning, and
all the coal saved the night before is more than used to get the house
or building “heated up”--while the people who should be comfortable
have to get up, bathe and take breakfast in chilly rooms. At no time
in the day is heat more wanted than about the time of getting up and
starting the day. A fire well cared for late in the evening makes a
warm house all night. And so it follows that it is much easier to add
a little more heat in the morning. And surely less coal is burned, for
the forcing of a fire part of the time often overheats, and wastes coal.

=First-day Firing.=--In the morning of _moderate winter weather_,
with the ash-pit draft damper open, before adding any coal allow the
fire to brighten up if it seems to be low; then (for such conditions)
spread over a thin layer of fresh coal and set the drafts for a brisk
fire. After the new fire is well started add as much coal as may be
necessary to last until next firing. Do not shake much if any--just
enough to give space for more coal. Then by setting the regulator (if
one is used), or, by closing the ash-pit draft damper and opening the
cold-air check damper a little, the boiler should keep up its work
until the next firing time.

In _severe weather_, if the boiler has been attended to at night as
directed in the section on “night firing,” the drafts can be turned on
and the boiler run for half an hour before adding coal. Or, if more
convenient to give it immediate attention, the grate can be thoroughly
shaken and enough coal added to last until mid-day. Often the cold-air
check damper will need to be entirely closed and the ash-pit draft
damper partly open if the heater is a water boiler. If a steam boiler,
the regulator should then be set to maintain the number of pounds of
pressure wanted and so left.

=Other-day Firing.=--In _severe weather_ more coal should be added
about noon, sometimes the draft may be left on for a few minutes and
then checked. And in such weather it is often well to give the boiler
further attention at five or six o’clock. In severest weather the
boiler should not be attended more than four times a day; and generally
not less than three times.

Often much coal is wasted by “nagging” the fire--poking, shaking and
feeding it until it becomes “dyspeptic.” A sure cure is a little common
sense in regular feeding, etc.

=Economy and Fuels.=--In running many boilers for _moderate weather_
better results follow if the grate is not shaken too much or too often.
Sometimes in _moderate_ weather a body of ashes on the grate checks the
fire and there is enough heat without a useless burning of fuel. Many
houses are overheated in _moderate_ weather and too much coal burned by
running the boiler as for zero weather.

So we repeat--_it is not wise to overshake or overfeed a boiler in
moderate weather_. The fire should be in such shape that if a change
comes at night there is a basis for a good fire to start on. When
the grate is shaken but once during the 24 hours (during _moderate_
weather) late at night is the best time.

When one stops to think that heating is needed during about 7 months
out of the year, and that _a greater portion of this time is usually
moderate weather_ when a very little heat is needed, it must be seen
that the science of running the heater to save coal is to apply common
sense rules of limiting the feeding and the attention in such periods.
In _severe weather_ we believe in giving the boiler a liberal quantity
of fuel regularly and at the right time. The time to save coal is when
there is no need for burning it. This is where a great many people make
errors in running the boiler--in forgetting to “let up” on the shaking
and feeding in moderate weather.

With some drafts and for boilers using hard coal or coke, good
economical results often are secured by opening the feed door a little
when it is desired to check the fire in moderate weather. This depends
on the draft.

=For Burning Soft Coal.=--Some types of boilers are made to burn
soft coal with economy, with least work. Some types are made
specially to burn the meaner grades of soft coal. Firing to prevent
smoke is a source of economy and these ways of running should be
followed--specially with large sectional boilers.

There are two types of soft coal, viz.: The free-burning coal, which
breaks apart when burning, allowing the gases to freely escape; and
the fusing-coking coal, which, when burning, first fuses into a solid
burning mass with a hard crust over the top, slowly coking as it burns.
The latter kind is most valuable for house-heating boilers because the
gases are more thoroughly consumed. The fusing-coking coal is worth
about 20 per cent. more for this purpose than the free-burning coal.

The gases should be allowed to pass off from the coal _slowly_. Leave
air inlet on the feed door open if draft permits. If possible, use
uniform sizes of coal. Avoid using coal having too much dust--the
“run-of-the-mine” may be lower in price but its heat-making value is
also low.

For the purpose of slow burning of soft coal, it is well in feeding at
night to let the fire burn up freely so that the coals are very live
with heat. Then fill in enough coal to last all night--leaving some of
the live coals uncovered if possible. With large sectional boilers this
exposure should be at the rear of the fire so that the flame will pass
over the live coals. Thus the gases coming off from the fresh coal are
burned and a larger amount of the full heat-producing value of soft
coal is made use of and with less smoke.

After a boiler is so fed, the dampers (unless an automatic regulator is
used) should be left about as follows:

Ash-pit draft damper open a little or closed, as draft may require.

Cold-air check damper open about one-eighth to one-third distance of
the opening.

Smoke-pipe damper about one-half closed.

A little experiment with the draft will usually tell the operator the
best way of leaving these dampers.

It will be found in the morning that the entire charge of coal is well
burned or partly coked.

The coked fuel, or that which sticks together in a mass, should be
broken up by the poker and more added generally as by rules given in
other sections.

It must always be remembered that the soft coals mined in different
parts of the country have widely varying heat-making capacities. To
obtain satisfactory results brands must be selected which have an
established reputation for excelling results in small boilers.

=For Burning Coke.=--It is best to keep the pot _full_ of fuel--keeping
a large body of coke under a low fire rather than a little fuel under a
strong fire.

It must be remembered that coke makes a very “hot fire” because the
coke is free-burning. Care should be taken not to leave drafts on too
long in boilers not having regulators.

Coke burns best for house-heating purposes with less draft than is
required for coal, therefore to keep a low fire the ash-pit draft
damper should be kept closed, and the smoke-pipe damper almost entirely
closed. The regulator (when used) can be set to keep the dampers about
as here advised. Coke is practically smokeless and its quick-burning
character makes a cut-off damper in the smoke pipe (which will stay
fixed as it may be set) quite necessary.

It is well to keep a layer of ashes on the grates and when shaking stop
before red-hot coals come through the grate. The coke then burns more
slowly, which increases its effectiveness.

With some drafts it may be well to “bank the fire” at night with
coke--pea coal size. This is a matter of experiment, and depends on the
character of the chimney draft.

Fire should be tended regularly--two times a day, or four at the

With an extra strong draft, at night the fuel should be packed down by
tamping with the back of a shovel.

With ordinary condition of draft, crushed coke, small egg size, should
be used.

=Other Rules for Water Boilers=--_To Fill System._--Open the feed-cock
when the heater is connected with a city or town water supply; if not,
fill by funnel at the expansion tank. Fill until the gage-glass on the
expansion tank shows about half full of water. In filling the system
see that all air cocks on the radiators are closed. Then beginning with
the lower floor, open the air cocks on each radiator, one at a time,
until each radiator is filled; then close the air cock and take the
next radiators on upper floors until all are filled, after which let
the water run until it shows in the gage-glass of the water tank. After
the water is heated and in circulation, vent the radiators by opening
the air valves as before. Then again allow the water to run into
the system until it rises to the proper level in the expansion tank

Always keep the apparatus _full of water_ unless the building be
vacated during the winter months, when the water should be drawn off to
prevent freezing. _Never draw water off with fire in the heater._

To draw off water, open the draw-off cock at the lowest point in the
system, and then open air cocks on all radiators as fast as the water
lowers beginning with the highest radiator.

=Air-vent Valves on Radiators.=--In order to secure the full benefit of
the heating surface of a hot-water radiator, the inside of the section
must be free of air. When a radiator is “air-bound” it means that parts
of the sections are filled with air in pockets which remain until the
air is allowed to pass off through the vent valve.

Air will gather from time to time at the highest points inside the
radiators, especially in those placed in the upper stories of the
building. These air accumulations inside cut down the working power of
a radiator exactly in proportion as they rob the inside of the casting
of proper contact with heated water. Air pockets not only reduce
effective heating surface, but they also prevent the circulation of hot

Therefore, it is well once in a while to take the little key provided
by the heating contractor and open the air valves on radiators to allow
the air (if any) to escape. When a radiator does not work as well as
usual, open the air valves until the water flows, which indicates that
the air has been fully released. Then close the valve.

=Valves on Cellar Mains.=--If cut-off valves have been placed on the
main and return pipes in the cellar, see that the valves on one line
of main and return pipes (at least) are open when the boiler is under
operation. Be sure that the system is open to circulate water through
the supply and return pipes before building a fire in the boiler.

=End of the Season.=--At the close of the heating season clean all
the fire and flue surfaces of the boiler. Let the water remain in the
system during the summer months. No bad results will follow if the
system is not refilled more often than once in 2 or 3 years. But,
generally, it is thought that best results are secured by emptying the
system once a year (after fire is out) and refilling with fresh water.

It is a very good idea to take down the smoke pipe in the spring,
thoroughly clean and put it back in place. Leave all doors open on the
boiler in the summer time.

=Other Rules for Steam Boilers=--_To Fill Boiler._--Open the feed-cock
when the heater is connected with city or town water supply; if not,
fill through the funnel. Let the water run until the gage-glass shows
about half full of water.

In the first filling, after the water has boiled, get up a pressure
of at least 10 pounds, draw the fire and blow off the boiler under
pressure through draw-off cock to remove oil and sediment, after which
refill with fresh water to the water line. This is best done usually by
the steam-fitter.

The damper regulator will control the pressure of steam, closing the
damper when the pressure is raised beyond the desired point and opening
the damper when the pressure falls below that point. By removing the
weight on the lever, different degrees of pressure can be kept up. The
regulator should be allowed to control the drafts without interference.

Examine the water glass often to see that the _water line_ is at the
proper height. If lower than normal open the supply pipe until the
water runs in and stands at the proper level. It is best when no water
stands in the glass, nor shows at the bottom of the try-cock, to
quickly dump the grate and do not put water into the boiler again until
it is cooled off.

If there is one or more shut-off valves on the main or return pipes,
before starting a fire see that one line of piping at least (main and
return) is open to circulate the steam.

=To Control Radiators.=--When it is desired to shut off steam from any
radiator (if the regular radiator valves are used), close the valve
_tight_, and when it is turned on see that the valve is _wide open_.
A valve partly turned off will cause the radiator to fill with water.
This rule applies only to one-pipe heating systems.

=The Air Valves.=--If little keyed air valves (sometimes called
“pet-cocks”) are used, follow generally the same directions as outlined
for hot-water radiators on page 49--only, of course, in releasing the
air from the radiator open the valve with the key provided and close it
just as soon as the steam unmixed with air comes through the nose of
the valve.

If “automatic” air valves are used they must be carefully adjusted by
the steam-fitter and then left to operate without undue interference.

=End of the Season.=--At the close of the heating season fill the steam
boiler with water to the safety valve and let it thus stand through the

Also thoroughly clean all the fire and flue surfaces of the boiler and
at the opening of the next season withdraw the water and refill with
fresh water to the water line, starting the boiler as before.

It is advisable to have a competent steam-fitter blow off the boiler
under pressure and thus give the inside a thorough cleaning when the
boiler is first set up and ready for fire.

A low-pressure boiler, using good water, rarely needs blowing off after
it is once cleaned at time of setting up.


The area of the flue should never be less than 8 inches in diameter
if round, or 8 by 8 inches if square--unless for a very small heating
boiler or tank heater. Nine or 10 inches round, or 8 by 12 rectangular
is a good average size. The flue should generally have a little more
area than that of the connecting smoke pipes.

Draft force depends very much on the height of the flue.

The chimney top should run above the highest part of the roof and
should be so located with reference to any higher buildings nearby that
the prevailing wind currents will not form eddies which will force the
air downward in the shaft. Often a shifting cowl which will always turn
the outlet away from the source of adverse currents will promote better

The flue should run as nearly straight up from the base to the top
outlet as possible. It should have no other openings into it but the
boiler smoke pipe. Sharp bends and offsets in the flue will often
reduce the area and choke the draft. The flue must be free of any
feature which prevents a free area for the passage of smoke. The outlet
must not be capped with any device which makes the area of the outlet
less than the area of the flue.

The best form of flue is a round tile--in such there is less friction
than in the square form and the spiral ascent of the draft moves in the
easiest and most natural manner.

If the flue is made of brick only, the stack should be at least two
4-inch courses in thickness.

If there is a soot pocket in the flue below the smoke-pipe opening, the
clean-out door should always be closed. If this soot pocket has other
openings in it--from fireplaces or other connections--such arrangements
are very liable to check the draft and prevent best action in the

The smoke pipe should not extend into the flue beyond the inside
surface of the flue, otherwise the end of the pipe cuts down the area
of the flue and injures its drawing capacity.

The inside of a flue should be smooth (pointed or plastered). When
the courses are laid with the mortar bulging out from the joints the
friction within the flue is very much increased. Often a troublesome
flue is corrected by lowering some sharp-edged weight by a rope which
should be worked against the sides of the flue until the clogging is
scraped off.

A new chimney when “green” will not have a good drawing capacity. Short
use dries out the mortar and better results follow.

=“Smokey” Chimneys.=--The failure of draft in flues may be due to a
variety of causes, one of which is illustrated in Fig. 57_b_. The short
chimney on the left side of the roof shows the course of the wind
as it passes over the ridge of the roof and why the draft in such a
chimney is retarded whenever this condition exists. The force of the
wind, as it comes into contact with the roof, causes a compression of
the air on the windward side and a rarification on the lee side. This
inequality of pressure causes a downward sweep of the wind as indicated
by the arrows. The effect on the low chimney is to retard the draft and
sometimes the pressure is great enough to reverse the action of the
flue and force the smoke into the house. The only remedy for such a
condition is an extension of the chimney that will raise its top above
the ridge.

[Illustration: FIG. 57_b_.--Effect of the wind in causing down draft in
low chimneys.]

The same effect is often produced by a neighboring building or a border
of trees that are higher than the chimney and dense enough to effect
the wind pressure.



The term plumbing is usually understood to cover all piping and
fixtures that carry water into the house and remove the waste material
in the form of sewage. It does not include the pipes of the heating
system. Although the work of installing heating plants is frequently
done by plumbers, pipe fitting and plumbing are two distinct trades.

In the process of building a house the rough plumbing is put into place
as soon as the structure is enclosed and the rough floors are laid.
The rough plumbing includes the soil pipe, into which the waste pipes
from the various fixtures empty, and those pipes which must occupy a
position inside the partition walls and beneath the floors.

The connections here described are for a city dwelling and apply to the
custom of local conditions. The same system might be used for a country
residence except in regard to the water supply and method of sewage
disposal. Plants of this type are discussed in the chapter on _septic

Fig. 58 shows a cross-section of the street, exposing the sewer _S_,
the water main _W_, and the connections with the house. The side of the
house has been removed to permit a view of the water and sewer pipes,
connecting with the bathroom, kitchen, laundry and other basement

The lateral sewer or house drain, which connects the house with the
street sewer _S_, is provided with a trap _G_, located, in this case,
just outside the basement wall. The house drain is made of vitrified
tile, laid so as to grade into the street sewer with the greatest
possible pitch. The sections are laid as true as conditions will permit
and the joints are all carefully filled with cement mortar to prevent
leakage. The object of the trap _G_ is to prevent sewer gas from
entering the house from the main sewer. The trap prevents the gas from
passing because the water in the bend of the trap forms a water seal,
beyond which the polluted air from the sewer cannot travel.

[Illustration: FIG. 58.--Cross-section of a city street showing the
watermain and sewer pipe with their connections to a dwelling.]

Next inside the trap is the vent pipe _E_, that extends to the surface
of the ground. In this case it is just outside the basement wall.
The top is covered with a metal cap. Another arrangement often made
to accomplish the same purpose is shown in Figs. 61 and 62, where a
piece of soil pipe in the form of a bend is made to take the place of
the cap. Inside the basement and extending up through the partition
walls to the roof is the _waste stack_ or soil pipe _A_. This pipe as
is explained in detail later, is made of cast iron and is put together
with calked lead joints. The top of the stack at the point where it
passes through the roof is shown in Fig. 59. In extending through the
roof the pipe _A_ must make a water-tight joint to prevent water from
leaking through. This is accomplished by means of the metal plate _D_,
which is set under the shingles and the piece _C_, that is soldered to
_D_. The joint between _C_ and _A_ is best made with lead the same as
the other joints of the stack. In the case of very high stacks, the
bottom should be supported by a pier or iron pipe rest. Besides being
supported at the base the stack should be secured to the side walls or
floor beams at each floor. This is to keep the pipe from moving out of
place and the consequent opening of joints.

[Illustration: FIG. 59.--Detail of soil pipe connection.]

[Illustration: FIG. 60.--Cross-section of cellar-drain.]

All of the waste pipes from the bathroom, kitchen and basement drain
into the waste stack. The cellar drain for draining the basement is
shown at _T_ in Fig. 58. It also appears in detail in Fig. 60. The
plate _B_, in the latter figure, is set flush to the surface of a
depression in the floor that serves as a collecting point for water.
The floor is constructed to drain toward this point. The plate is
perforated to let the water through and is generally hinged so that
in case of stoppage the cover may be raised. The bell-shaped piece
under the cover surrounds the piece _C_, to form a water seal when the
level of the water is at _A_. In addition to this water seal there
is generally a trap between the drain and the sewer as shown in the

The method of connecting the bathroom waste pipes with the stack is
shown in Fig. 99 and will be described later. All of the sewage of the
house is emptied into the stack by the most direct route, and from the
stack it is conducted as directly as possible into the sewer. From the
drawing it will be seen that all openings to the sewer are sealed in
two separate places, once at the outlet to prevent the air from the
street sewer entering the house drain _G_, and again at each opening to
prevent escape of the sewer gas from the drain into the house.

[Illustration: FIG. 61. FIG. 62.

FIG. 61.--House drain with outside vent, and running trap placed inside
the basement wall.

FIG. 62.--House drain with outside vent, and running trap placed
outside the basement wall.]

The openings at _E_ and _A_ at each end of the stack permit a constant
circulation of air for ventilation. The length of the stack and its
location causes it to act as a chimney and the draught produced takes
the air in at _E_, and discharges it at the top. In large houses there
is sometimes added a vent stack to produce further ventilation, but
in the average dwelling the arrangement here shown covers the common

In Figs. 61 and 62 are shown in detail two methods of arranging
the sewer connections in the basement to permit of the removal of
obstructions in case the pipes at any time become stopped. The trap,
vent, etc., are easily recognized. With the arrangement as shown in
Fig. 62, the clean-out is so placed as to give access to the inside
of the pipe. Should an accumulation or obstruction of any kind become
lodged in the pipe, the stop in the clean-out is removed and a
flexible metal rod is used to remove the stoppage. The trap outside the
wall has an opening through which the obstruction may be reached in
case it cannot be removed from the first clean-out. The disadvantage in
using the outside trap, as here shown, is that it can be reached only
by excavation.

Fig. 61 shows another common method of installation. Here the trap is
placed inside the basement wall. This gives an easier means of opening
the trap than Fig. 62 affords and accomplishes the same purpose. The
connections with the stack are the same as in Fig. 62. Obstructions in
the sewer pipe are most likely to become lodged in the trap and for
this reason the trap should occupy a position that is reasonably easy
of access.

The outside trap as described above is quite generally installed in
buildings of all kinds, but its use is by no means universal. In some
communities it is not used at all, and many plumbers consider it only
an added means of causing stoppage and an extra expense to install.

The object of the outside trap is to keep the air of the street sewer
from entering the house drain. It is at once inferred that the air
of the street sewer is more dangerous than that of the house drain.
The street sewers, however, are ventilated at each street corner and
at each manhole. There cannot then be much difference in the air of
the two places. The traps on the fixtures that prevent sewer gas from
entering the house would be just as efficient if the outside trap did
not exist.

While the methods shown in Figs. 61 and 62 are considered good
practice, there is considerable objection to the vent being placed near
the dwelling, because of the sewer gas that is forced out, whenever
a sudden discharge of water goes into the drain. Each time a closet
is flushed, a large volume of water enters the stack and completely
fills the pipe. When this occurs, the descending water forces out the
air of the pipe ahead of it, and a gush of offensive air filled with
sewer gases is forced out of the vent. It is evident that such a vent,
located near an open window or where it will reach the nostrils of the
inhabitants is a thing not greatly to be desired.

Outside traps when placed near the surface sometimes freeze. The
circulation of air through the vent is occasionally sufficient in cold
weather to freeze the water and stop the trap.

[Illustration: FIG. 63.--Corporation cock with lead connecting pipe.]

=Water Supply.=--The water supply taken from the street main is
conducted to the house by the pipe shown in Fig. 58, at _C_. This pipe
is generally of lead as piping of that metal is the most durable for
underground work. Iron used under the same conditions will last only
a few years. The connection is made with the water main by use of a
_corporation_ cock. This is a special style of cock that is shown in
Fig. 63. In the figure the cock is connected with a short piece of lead
pipe that is used for making connection with the service pipe in the

[Illustration: FIG. 64.--Curb cock as it appears attached to the
service pipe.]

Located at the left of _C_, in Fig. 58, is the _curb-cock_, used
for shutting off the water from the city lot. The curb-cock, being
underground, is reached through an iron tube by means of a wrench
attached to a long iron rod. The curb-cock has a protective covering
in the form of an iron pipe. The lower end of the pipe screws into the
body of the cock. The top end comes just above the grade line of the
curb and is covered with an iron screw-cap. The curb-cock is shown in
detail in Fig. 64. The pipe _B_ is fastened to the valve at _D_ and A
is the screw-cap. In opening and closing the wrench fits over the part
_C_ of the valve.

On entering the building the supply pipe should be provided with a
_stop_ and _waste-cock_ for shutting off the water from the house and
draining the pipes that compose the system of circulation. At _V_, in
Fig. 58, is indicated a stop and waste-cock with the waste pipe _B_
connected with the sewer. This cock is shown in detail in Figs. 65 and
66. The cock is so made that when closed there is a small opening at
_A_, that allows the water from the system to escape through the waste

From the water supply, the cold-water pipes may be traced in the
drawing directly to each of the fixtures of the house. The hot-water
pipe leaves the range boiler at the top and connects with each fixture
using hot water, thus making the circuit complete. Details of the
piping which provides hot water is described under range boiler, page

[Illustration: FIG 65.--Stop and drain cock with lever handle.]

[Illustration: FIG. 66.--Stop and drain cock with =T= handle.]


The development of modern plumbing has brought about the use of a
great number of household mechanical appliances, that have received
trade names little understood by the average person. The lack of
distinguishing terms, or language in which to describe plumbing
fixtures, often leads to embarrassment, when such articles are to
be described to workmen. Common household valves and cocks are so
classified by the trade, that mistakes are often made in their
designation, because of a limited knowledge of the use of the various
articles. A little consideration of the different classes of fixtures
will make it possible to state to a tradesman the exact article in

The term _valve_ is intended to define an appliance that is used to
permit, or prevent, the passage of a liquid through the opening or port
which it guards. The term is so general in its application that there
are hundreds of different kinds of valves. Even for a single purpose
there are many styles of a given kind.

A _cock_ was originally a rotary valve or spigot used for drawing
water. Today there are many kinds of cocks that are not rotary in their

It would be impossible in this work to describe in detail all of
the kinds of cocks and valves used in household plumbing. It will,
therefore, be the aim to confine attention to one article of a type
and to choose such examples as are in general use and that are good
representatives of their classes.

[Illustration: FIG. 66_a_.--Kitchen sink with Fuller bibb-cocks.]

=Bibb-cocks.=--On the kitchen sink, the water faucets, such as those
shown in Fig. 66_a_, are termed bibb-cocks by the plumber. If the
nozzle is plain, it is a _plain bibb_. If the nozzle is threaded so
that a hose connection may be attached as in Fig. 67, it is a _hose
bibb_. Bibb-cocks are found in three general styles: compression bibbs,
ground-key bibbs, and Fuller bibbs. The compression bibb takes its
name from the method of closing the valve. Fig. 68 gives an example
of its mechanical construction. This is a plain _solder bibb_ because
the shank _A_ is to be attached by a solder joint. If the part _A_
contained a thread to make a screw joint, such as Fig. 67, it would
be a plain, compression, _screw bibb_. Fig. 68 is another style of
compression bibb-cock, largely used on sinks; this cock, being finished
with a flange, is a _compression flange bibb_.

[Illustration: FIG. 67.--Compression hose bibb.]

[Illustration: FIG. 68.--Compression flange bibb.]

[Illustration: FIG. 69.--Cross-section of plain compression bibb-cock
for a solder joint.]

Fig. 69 shows quite clearly the mechanical arrangement of the
compression cock. When the handle is turned the nut _C_ lifts the valve
from its seat _B_, allowing the water to escape. The piece _D_ is
generally made of composition rubber that may be bought at the dealers
for a trifling amount but it may be replaced temporarily with a piece
of leather. The part _E_ is packing, to keep the water from leaking
out around the stem. The packing may be obtained from the dealer
especially for the purpose or it may be made of a disc of sheet rubber.
In fact, anything that can be put into the space will answer the
purpose temporarily. The valve is closed by compression, hence the name
compression cock. All cocks made to open and close in the same manner
are compression cocks.

[Illustration: FIG. 70.--Cross-section of plain self-closing bibb-cock
for lead pipe.]

[Illustration: FIG. 71.--Cross-section of lever handle, plain bibb.]

[Illustration: FIG. 72.--Cross-section of plain Fuller bibb for lead

=Self-closing Bibbs.=--In Fig. 70 is one example of the many styles of
self-closing bibb-cocks. When the handle of this cock is turned, the
steep-pitched screw _A_ opens the valve and at the same time compresses
the spiral spring _B_, when the handle is released, the valve is
pressed back on its seat by the spring. Self-closing cocks are used to
prevent the waste of water at drinking fountains, wash basins and other
places where the water is apt to be left running through carelessness.

=Lever-handle Bibbs.=--Fig. 71 is an example of the _lever-handle_,
_ground-key_ bibb-cock. The key is the piece _A_, which is tapered and
forms a ground joint with the part _B_. The cock takes its name from
the form of the handle. The term ground-key means that the key has been
ground into place with emery dust. This cock is kept from leaking by
adjustment of the screw _C_.

=Fuller Cocks.=--These cocks take their name from their inventor. They
are made to suit every condition for which water cocks are used. Their
universal use attests to their utility and excellence in service. Fig.
72 shows the principle on which all Fuller cocks work. The varying
conditions under which the cocks are used require a great many forms,
but the working principle is the same in all. In these cocks, the
valve is a rubber plug or ball that is drawn into the opening by an
eccentric piece attached to the handle. The piece _D_ in the drawing
is the rubber plug that is drawn against the opening by the crank _B_,
which is worked by the lever handle _A_. This cock may be repaired, in
case it leaks, by unscrewing it at the joint nearest the plug. A wrench
and a pair of pliers are all the tools required. The pieces _D_ must
be obtained from the dealer. The part _J_ is the packing that keeps
the water from leaking out around the stem. The screw-cap _H_ forces a
collar _I_ down on the packing to keep it water-tight.

[Illustration: FIG. 73.--Repairs for Fuller cocks.]

The parts for the Fuller cock that may be obtained for repair are shown
in detail on Fig. 73. The ball, which appears in Fig. 73 at _D_, is the
part that receives the greatest amount of wear. If the cock at any time
fails to stop the flow of water, a new ball may be put in place by the
aid of a wrench and a pair of pliers. The water being first shut off
from the system, the cock is unscrewed and the cap _E_ removed with a
pair of pliers. The worn ball is then removed and a new one substituted.

=Wash-tray Bibbs.=--A special style of cock is made for laundry wash
trays in both the Fuller and compression types. Of these the Fuller
type is the most convenient as the handle is placed on the side and but
one movement is required to open the cock. This style of cock is used
on the wash trays shown in Fig. 83.

=Basin Cocks.=--Water cocks for wash basins are made in two general
types--the compression and the Fuller types of cocks. Their mechanism
is much the same as for other similar styles adapted to the use for
basins. The self-closing cocks used so largely on wash basins are
compression cocks. Fig. 74 is an example of Fuller basin cock in
general use. Compression cocks for the same purpose are shown on the
wash basin in Fig. 90.

[Illustration: FIG. 74.--Fuller basin cock.]

=Pantry Cocks.=--In general form, pantry cocks are the same as those
used for basins except that the outlet is elongated.

[Illustration: FIG. 75.--Sill cock in place attached to the water pipe.]

[Illustration: FIG. 76.--Cross section of sill cock.]

=Sill Cocks.=--As a means of attaching garden hose or lawn sprinklers,
sill cocks are placed on the side of the building at any place
convenient for their use. Fig. 75 illustrates the method of attaching
the cock to the water supply. Fig. 76 shows in cross-section its
mechanical arrangement. The part _A_ is screwed into the water supply,
and _B_ furnishes the hose attachment. The valve is operated the same
as any other compression valve. In Fig. 75 the cock is shown at _A_
with a garden hose attached. The pipe to which _A_ is attached passes
into the basement and connects to the water supply. The stop-cock _B_
is used to shut off the water. When the stop-cock _B_ is closed, _A_
should be opened, so that the pipe will drain. If this is neglected
during freezing weather, the pipe is apt to freeze and burst.

=Valves.=--The distinction between a cock and a valve is not at
all definite. Custom has determined that in certain places a cock
shall stop the flow of a liquid but in another place, perhaps of a
similar nature, a valve shall accomplish the same purpose. The chief
distinction between a cock and a valve is that of its external form.

In Figs. 77, 78 and 79 are three examples of valves that are very
generally used on pipes carrying any kind of fluid. The valves are
shown in cross-section to display the arrangement of the mechanism.

[Illustration: FIG. 77.--Cross-section of globe valve with detachable
valve disc.]

[Illustration: FIG. 78.--Cross-section of angle globe valve.]

[Illustration: FIG. 79.--Cross-section of gate valve.]

Fig. 77 is an example of the common _globe-valve_. The name was
originally intended to define a valve the body of which was in the form
of a globe. The hand-wheel _H_, attached to the screw-stem _S_, raises
the valve _A_ when desired. The valve makes close contact with the
seat _C_, by means of a composition rubber disc _B_. The disc _B_ may
be renewed when worn out as in the case of the radiator valve already

Fig. 78 represents an _angle globe-valve_. In general construction it
is quite similar to Figs. 14 and 15, but the valve _V_ in this case
is a cone-shaped piece of brass, which makes a seat in a depression
provided for it. The valve _V_ and the seat are formed as desired and
then ground into contact with emery dust or other abrasive material, to
assure a perfectly tight joint. When this valve becomes worn and begins
to leak, it may be repaired by regrinding, but such work requires the
services of a pipe-fitter. The tendency of modern practice is to use
valves with the detachable discs, such as that of Fig. 77, because they
are easily repaired.

The valve shown in Fig. 79 is known as a _gate-valve_. The upper part,
including the screw and stem, is the same as the globe style but the
valve proper is made in the form of two flat gates _A-A_. When the
valve is closed, as it appears in the drawing, the gates are forced
against the seats by the cone-shaped piece _B_, which acts as a wedge,
to tightly close the opening. When the hand-wheel is turned to open the
valve, the gates are raised and are taken entirely out of the path of
the flowing liquid. Gate-valves are used in places where it is desired
to obstruct the flow as little as possible. They are somewhat more
expensive than globe-valves but are considered worth the extra expense
in service.

=Kitchen and Laundry Fixtures.=--The development in modern plumbing has
wrought many changes in the styles of household fixtures but none has
been so great as that in the kitchen sink. The old style, insanitary,
wooden sink has been almost entirely replaced by those made of pressed
steel or enameled iron. They are made in every desired size and to
suit all purposes. They may be plain or galvanized as occasion may
require, or the enameled sink is obtainable at a very slight addition
in price. The enameled sink has reached a degree of perfection where
its durability is unquestioned, and as a consequence kitchen furniture
is vastly improved at but little advance in cost.

[Illustration: FIG. 80.--Model kitchen.]

[Illustration: FIG. 81.--White enamel kitchen sink.]

A modern kitchen in which gas is used as fuel is shown in Fig. 80.
Simplicity and neatness of arrangement are the noticeable features.
This kitchen is intended to suit the average-sized dwelling and
contains all necessary plumbing, cooking and heating apparatus. The
hot-water boiler is here shown attached to an instantaneous heater. The
common kitchen sink is supplemented with a slop sink and covered with
a drain board. This simple kitchen may be elaborated to any extent.
Fig. 81 shows a kitchen sink of white enamel with two enameled drain
boards. The drain boards are sometimes covered with perforated rubber

[Illustration: FIG. 82.--Model laundry.]

[Illustration: FIG. 83.--Enamel wash trays in a basement laundry.]

In Fig. 82 is shown an example of the modern basement laundry. The
wash-boiler heater is shown on the left. An automatic instantaneous
water heater is on the right. The stationary tubs or wash trays occupy
the center of the picture. In detail these wash trays appear in Fig.
83. These are enamel-covered ware and are provided with the wash-tray
bibb-cocks described above. This type of plumbing represents the most
modern of sanitary arrangements.


With the present-day improvements in plumbing, and the perfection
in the manufacture of porcelain and enameled iron, the bathrooms of
houses of moderate cost have become places of cleanliness, attractive,
relatively free from offending odors and supplied with all necessary
sanitary fixtures.

[Illustration: FIG. 84.--Model bath room for the average dwelling.]

Enameled iron has reached a state of perfection where it rivals
porcelain in beauty. The forms of the various bathroom pieces have been
modeled for convenience in use and grace of form, at the same time the
strife of the designer has been to produce articles that not only look
well but are convenient and easily kept clean.

Bathrooms need not be expensive in order to be convenient, attractive
and useful. The bathroom shown in Fig. 84 is such as is installed in
dwellings of moderate price. It possesses every feature necessary
to usefulness and comfort. In this room the furnishings are all of
enameled iron. The floor is covered with linoleum and the wainscoting
with enamel paint.

=Bath Tubs.=--Bath tubs are made in sizes that vary in length from
4-1/2 to 6 feet. They are constructed in a variety of forms and of
materials to suit all conditions of service. For domestic use they
are very generally made of enameled iron. This form of construction
produces serviceable and handsome furnishings for the bathrooms of the
modest house as well as for the sumptuous bath of the most pretentious
residence. An elaboration of Fig. 84 might include the Sitz bath
shown in Fig. 85 and the fittings may be chosen from a great variety
of forms. The recent styles of enameled tubs are, in design, much
handsomer than those with the roll rim and in form such as permits a
clean room with the minimum of labor. They are also provided with more
convenient water and drainage fixtures.

[Illustration: FIG. 85.--Sitz bath.]

The tub of Fig. 86 sets flat on the floor and makes a close joint with
the wall. It thus prevents the accumulation of dust that is difficult
to remove. In addition the fixtures are arranged in a more commodious
manner and the general appearance is most pleasing. The arrangement
of the fixtures in Fig. 87 gives still greater convenience and being
arranged with a shower and protecting curtain, provides all of the
conveniences of a luxurious bath without greatly increased cost over
the simple tub. The fixtures in this design are all in position of
greatest convenience and attached to pipes that are concealed in the

[Illustration: FIG. 86.--Enameled iron bath tub.]

[Illustration: FIG. 87.--Bath tub with shower.]

The fixtures usually provided with the tub are double Fuller or
compression cocks for hot and cold water, the overflow and strainer,
for the discharge of the water into the sewer in case the tub
overflows, and a drain and bath plug.

The double Fuller cock is shown in Fig. 88. It is made to open
and close by the same sort of mechanism as is shown in Fig. 71, a
description of which appears on page 90.

[Illustration: FIG. 88.--Double Fuller cock for bath tubs.]

The overflow is shown in detail in Fig. 89. The part _A_ appears inside
the tub. It is made water-tight around the edge _C_ by a rubber washer
that is clamped tight to the surfaces by the nut _B_. In case of
leakage, the overflow may be removed for repair by unscrewing the union
attached to the piece _D_ and removing the nut _B_.

[Illustration: FIG. 89. FIG. 89_a_.

FIG. 89.--Overflow attachment for bath tubs, lavatories, etc.

FIG. 89_a_.--Drain attachment for bath tubs, lavatories, etc., showing
locknut and union connection.]

The drain-pipe connection is shown in Fig. 89_a_. The plug _D_ and the
flange _A_ show inside the tub. The flange is made water-tight by a
rubber washer that the nut _B_ clamps tight to the tub. The part _C_
is a union which permits the tub to be detached from the drain pipe.
Repairs to this joint may be made as in the overflow.

[Illustration: FIG. 90.--Old style marble finished lavatory.]

[Illustration: FIG. 91.--Types of lavatory plumbing not now used in
good practice.]

=Wash Stands and Lavatories.=--Wash stands for bathrooms are obtainable
in many forms, either plain or ornate, to suit every condition and
style of architectural finish.

[Illustration: FIG. 92.--Enameled iron wall wash basin.]

[Illustration: FIG. 93.--Enameled iron pedestal wash basin.]

They are made in marble, porcelain and enameled iron, the last being
the most commonly used. They are made to suit the part of the room to
be occupied, whether that is against a wall, a corner, or to stand on
a pedestal on the floor. Those intended to fasten to the wall may be
supported by brackets or suspended at the back from pieces secured in
the wall.

In Figs. 90 and 91 are shown samples of marble-finished wash basins.
In former years basins of this type were very much in use, and until
the introduction of the modern porcelain and enameled ware, it was the
highest type of sanitary plumbing. The water cocks and traps are of the
same style and grade as appear on the most modern examples of enameled
ware of Figs. 92, 93 and 94. The water cocks used in Fig. 90 are of the
compression type. All of the others are of the Fuller type. The basin
in Fig. 93 is provided with extra shut-off cocks on the water pipe
under the basin. They are added to the plumbing merely as a convenient
means of shutting off the water for repair. The wash stand is usually
provided with hot and cold water cocks, a waste pipe with its traps and
overflow connections.

[Illustration: FIG. 94.--Corner wash basin.]

=Traps.=--The waste pipes from the wash basin and bath tub are always
provided with some form of trap, to prevent air from entering the room
from the sewer, charged with offending odors. Traps are made in many
forms, but the purpose of all is to prevent the escape of sewer gas.
The plain trap _S_, shown in Fig. 95, is that used under the basin in
Fig. 91. It makes a tight joint by means of the nut _B_ and a rubber
washer as in the case of other joints of the kind. The parts _C_ and
_E_ are unions that permit the pipe or bowl to be removed without
disturbing the remainder of the plumbing. From the form of the trap
it will be seen that the U-shaped part below the dotted line _F_ will
always remain full of water and so prevents the escape of air from
the sewer. In case the trap becomes stopped the obstruction will
likely become lodged in this part of the pipe. To clean the trap the
screw-plug _D_ is taken out with a pair of pliers and the obstruction
removed with a wire.

The traps used in Figs. 90 and 92 are the same in principle as Fig. 95
but are made to discharge into a pipe placed in the wall instead of
under the floor. The trap in Fig. 94 is a form known as the bottle-trap
that is sometimes used in the more expensive plumbing.

[Illustration: FIG. 95.--The S trap of nickel-plated brass tubing.]

[Illustration: FIG. 96.--The Bower non-siphoning trap.]

[Illustration: FIG. 97.--The drum type of non-siphoning trap.]

[Illustration: FIG. 98.--An S trap made of lead pipe.]

Another style much used with lavatories is the Bower trap shown in Fig.
96. In this trap the water comes down the pipe _B_ and pushing aside
the hollow rubber ball _A_, enters the space surrounding it and is
discharged at _C_. The ball, being light, is held against the end of
the pipe by the water and acts as a stopper to prevent evaporation from
taking place. Open traps, such as Fig. 95, if left standing for a long
time, may lose sufficient water by evaporation to destroy the water
seal and allow the sewer gas to escape. In the use of the Bower trap
such occurrence is much less likely to take place.

Fig. 97 is another trap much used on sinks; it is known under the
trade name of the Clean Sweep trap. The part _C_ is much larger than
the common trap and the water seal is less likely to be broken. The
clean-out is larger and the interior is easy of access in case of

The simplest and most commonly used trap in cheap plumbing is that of
Fig. 98. It is a lead pipe bent in the form of an _S_. It is the same
in shape as Fig. 95 and performs its work as well but does not have the
means of detachment shown in the latter. Traps of many other forms are
in use but all have the same function to perform and the mechanical
make-up is much the same as those described.

[Illustration: FIG. 99.--A method of bath-room plumbing using the drum

The plan of attachment of the various bathroom fixtures of the soil
pipe must always depend on local conditions. The object is to conduct
the waste water to the sewer in such a way as to give the least
opportunity for stoppage and to prevent sewer gas from escaping into
the house. To accomplish this purpose the pipes and traps are arranged
according to a plan proposed by the architect, plumber or other person
familiar with the principles of plumbing. Since these pipes are
placed in the walls and under the floors, where they are not readily
accessible, it is necessary that their arrangement be made with care
and that the workmanship be such as to assure correct installation.

In Fig. 99 is shown a common method of connecting bathroom fixtures
with the sewer. The drawing shows a bathroom with the floor broken away
to show the pipe connections with the bath tub, wash basin and closet.
The overflow pipes _O_ and _V_ and the drain pipes _D_ and _R_ from
the wash basin and bath tub empty into a large lead drum-trap _T_, set
under the floor. This trap takes its name from its shape. It is set
in position as dictated by the conditions under which it is used. The
nickeled plate _P_, screwed into the top of the trap, comes just above
the bathroom floor. This plate is easily removed in case of stoppage.
It is made air-tight by a rubber ring placed under the cover and which
makes a joint with the top edge of the drum.

It will be noticed that the waste pipes from the bath tub and wash
basin enter the trap near the bottom and discharge at the opposite side
near the top. The water will stand in the trap and pipes level with
the bottom of the discharge pipe and thus form a seal that prevents
the escape of sewer gas. This is a common form of non-siphoning trap.
It is non-siphoning because it cannot lose its seal by reason of the
siphoning effect of the water as it passes through the waste pipes
on its way to the sewer. Another form of non-siphoning trap is the
clean sweep trap shown in Fig. 97. Such traps as Figs. 95 and 98 are
siphoning traps, since it is possible, in this form of trap, for the
water to be so completely siphoned that not enough remains to form
a seal. The small drawing, marked _Detail L_, is another method of
connecting the same arrangement of fixtures. The waste pipe enters the
trap as before but discharges immediately opposite. The level of the
water stands in the pipes as indicated by the dotted line.

=Back-venting.=--To prevent the possibility of loss of seal by
siphoning and the escape of sewer gas, traps are back-vented to the
main stack or to a separate vent stack. The venting is accomplished by
joining a pipe to the top of the trap or to some point in its immediate
neighborhood, and connecting this with the main stack or the vent
stack. The water in a trap so vented will be open to the air from both
sides and consequently can never be subject to siphonic action.

In the average-sized dwelling where non-siphoning traps are used,
back-venting is not necessary, but in large houses and in plumbing
where siphon traps are used, vent pipes must be attached to the traps
to assure a satisfactory system.

Fig. 100 furnishes an example of back-venting, applied to the bathroom
shown in Fig. 99. In the former figure the bath tub and wash basin
are connected with the waste pipe by siphon traps. A siphon trap may
lose its seal in two ways: by self-siphonage, or by aspiration caused
by the discharge of the water from other fixtures. In the discharge
of the siphon trap, such as _B_, in Fig. 100, the long leg of the
siphon, formed by the discharge pipe, may carry away the water so
completely that not enough remains in the trap to form a seal. Again,
the discharge of the water from the bath tub through the waste pipe
tends to form a vacuum above it and in some cases the seal in _B_
is destroyed by the water being drawn into the vertical pipe. The
possibility of either of these occurrences is prevented by back-venting.

[Illustration: FIG. 100.--An example of back-vented plumbing as applied
to the bathroom.]

In Fig. 100, a pipe from the main stack is connected with the bend of
the trap at _B_ and also to the waste pipe outside the trap at _T_. A
vent is also taken from the drain _C_, at a point just below the trap
in the closet seat. The object of all of the vents is to prevent the
tendency of the formation of a vacuum from any cause that will carry
away the water seal of the trap and allow sewer gas to enter the house.

The closet seat also contains a trap which will be described later. It
connects with soil pipe _S_, leading to the sewer by a large lead pipe

All of the pipes under the floor, leading to the soil pipe, should
be of lead. The pipes above the floor are generally of iron or
nickel-plated brass. All of the connections in the lead pipes are made
with _wiped joints_; that is, the connections are made by wiping hot
solder about the joint, in a manner peculiar to this kind of work, in
such a way as to solder the pipes together. The joints made in this
manner are perfectly and permanently tight. Lead pipes are used under
such conditions, because lead is the least affected by corrosion of any
of the metals that could be used for such work.

=Soil Pipe.=--The soil pipe, of which the waste stack or house drain is
composed, is made of cast iron and comes from the factory covered with
asphaltum paint. It may be obtained in two grades, the standard and
extra heavy. The only difference is in the thickness of the pipe. The
former is commonly used in the average dwelling. One end passes through
the roof and the other end joins to the vitrified sewer tile under the
basement floor. The joints must be perfectly tight, because a leak in
this pipe would allow sewer gas to escape into the house. One end of
each section is enlarged sufficiently to receive the small end of the
next section. The joints are made with soft lead. The pipes are set in
place and a roll of oakum is packed into the bottom of the joint, after
which molten lead is poured into the joint, filling it completely. The
oakum is used only to keep the lead in the joint until it cools. After
the lead has cooled it is packed solidly into the joint with a hammer
and calking tool. The calking is necessary because the lead shrinks
on cooling and makes a joint that is not tight. Well-calked joints
of this kind are air-tight and permanent. _Detail N_ (Fig. 99) shows
the arrangement of the parts of the joint as indicated at _A_. The
blackened portion represents the lead as it appears in the joint.

_Detail M_ (Fig. 99) shows the methods of attaching the closet seat
to the lead waste pipe _C_. The end of the lead pipe is flanged at
the level of the floor, as shown at _C_ in the detail drawing. The
depression _D_, around the connection, is then filled with glazier’s
putty and the seat is forced down tightly in place and fastened with
lag screws.

The pipe _C_, from the closet, and that from the trap _T_, being of
lead, a special joint is necessary in connecting them with the soil
pipe, because a wiped joint cannot be made with cast iron. To make such
a connection the end of the lead pipe is “wiped” onto a brass thimble,
heavy enough to allow it to be joined to the soil pipe by a calked lead
joint. The brass thimble is then joined to the cast-iron pipe by a
calked lead joint.

[Illustration: FIG. 101.--The wash-out closet.]

[Illustration: FIG. 102.--The wash-down closet.]

=Water Closets.=--Water closets are made in a great number of styles to
suit the architectural surroundings and the various conditions under
which they are to be used. Many forms of water closets are manufactured
to conform to special conditions, but those commonly used in the
bathrooms of dwellings are of three general types. The mechanical
construction of each is shown in the following drawings, Figs. 101,
102 and 103 showing respectively in cross-section the principle of
operation of the _washout_ closet, the _washdown_ closet and the
_siphon-jet_ closet.

_Washout Closets._--This type of closet has in the past been used to
a very great extent. It does not perform the work it has to do, so
perfectly as the others, because the shallowness of the water in the
bowl allows it to give off odors, and because it is difficult to keep
clean. The action of the closet is as follows: When the closet is
flushed the water enters the rim at _A_, and the greater portion of
it is washed downward at _B_ to dislodge the contents of the bowl. A
lighter flush is sent through the openings in the side, which serves
to wash the entire surface. The direction of discharge is forward,
where it dashes against the front of the bowl and then falls into
the trap. The only force received to carry the water to the trap is
from falling through the distance from the point where it strikes the
front. The flushing action is obtained from the use of a large volume
of water. As the discharged matter is dashed against the front of the
bowl, the flushing action of the water is not sufficient to remove all
the stains; the result is an accumulation of filth. This part of the
bowl is out of sight; hence, it is seldom kept clean. The name washout
comes from the action of the water to wash out the contents of the bowl.

[Illustration: FIG. 103.--The siphon-jet closet.]

[Illustration: FIG. 104.--A poor design of wash-down closet.]

=Washdown Closets.=--As shown in Fig. 102, the action of this closet is
to wash the contents of the bowl directly down the soil pipe. The depth
of the water at _A_ is much greater than at the corresponding point in
the washout closets; as a consequence fecal matter is almost submerged.
The main objection to this closet is that it is noisy. Fig. 104 shows
another form of washdown closets. This closet is open to objection
because of faulty design; the part _A_ is difficult to keep clean
because of its shape.

=Siphon-jet Closet.=--What is considered by many to be the most
satisfactory closet yet designed, is that of the siphon-jet type shown
in Fig. 103. The flushing action of this closet is entirely different
from that of the others described. The flushing water enters at _A_
and fills the rim _B_. Part of the water washes the sides of the bowl,
while the remainder flows through the jet _C_, and is discharged
directly into the outlet. The ejected water enters the outlet _D_,
which, as soon as it fills, acts as a siphon to draw the water into
the soil pipe. This closet is most positive in its action, since
the discharge is made by the siphon and also receives the additional
momentum due to the water flowing through the jet. Its action is
attended with but little noise.

[Illustration: FIG. 105.--Siphon-jet closet with the high flush tank.]

[Illustration: FIG. 106.--Form of closet not now used in good practice.]

=Flush Tanks.=--The water closet depends for its action on one of two
general types of flush tanks, the high and the low forms. The tank
is automatically filled with water and when wanted, a large volume
of water is suddenly discharged into the sewer, carrying with it the
contents of the seat. The tank again fills and is ready for use when

As illustrations of high flush tanks, those shown in Figs. 105 and 106
furnish examples of a simple and efficient form. The details of the
mechanism of this type of tank are shown in Fig. 107. The pipe from the
water supply is attached at _G_ to the automatic valve _F_, which keeps
the tank filled with water. The piece _F_ of the valve is held against
the opening by the pressure exerted through the float _E_. The float is
a hollow copper ball. As the ball is lifted it exerts a pressure in
proportion to the amount it is submerged. When the water reaches the
level _A-A_, the valve is tightly closed. As the water is discharged
from the tank the ball follows the level of the water and opens the
valve, allowing the water to enter and again fill the tank.

[Illustration: FIG. 107.--Details of construction of a simple type of
siphon flush tank.]

The siphon is made of cast iron, and in the figure is shown cut through
the center. The lower end fits loosely in the piece _K_, and makes a
water-tight joint around its outer edge, by resting on a rubber ring
_C-C_. The right-hand side of the siphon is open at _H_, and when the
tank is full, the level of the water is at _A-A_, which is almost
at the top of the division plate. To discharge the tank, the chain
_L_, attached to the lever _B_, is pulled down; this action raises
the siphon from its seat. As soon as the siphon is lifted, the water
rushes through the opening around _C-C_, into the pipe _K_; this causes
a partial vacuum to form in _D_, and the water is lifted over the
division plate _K_, and flows out at _D_, forming the siphon. As soon
as the siphonic action begins the siphon may be dropped back on the
seat and the water will continue to discharge until the tank is empty.

=Low-down Flush Tank.=--The low-down flush tank for water closets has
met with so much favor that it has to a great extent displaced the high
tank. The reason for this is because of its advantages over the other
style. The low tank is more accessible, more easily kept clean, and
better adapted to low ceilings. It is used successfully as a siphon
tank, but other forms are in use with satisfactory results.

Fig. 108 gives a perspective view of one style of this type of tank
attached to a siphon-jet closet. Figs. 109 and 110 give the details of
the construction of two forms of this type of tank, both of which have
given efficient service. The drawing shows the tanks with the front
broken away to give a view of the working parts. The water enters the
tank and is discharged at the points indicated. The float and supply
valve works exactly as described in the high tank. The drawing in Fig.
109 shows the tank in the act of discharging. The discharge valve is
raised as shown at _E_. When the water is completely discharged, the
float occupies the position shown dotted. When the float reaches this
dotted position, its weight pulls down the piece _A_. This releases
the lever _B_, and the attached stopper _E_, which falls and closes
the discharge orifice. While the tank is filling with water, a stream
flows through the small pipe _D_, to replenish the water in the closet
that has been discharged in siphoning. When the tank is full of water,
the pieces _A_ and _B_ occupy the positions shown dotted. To discharge
the tank the _trip_ is pushed down. This action raises the lever to
the position _B_, and with it the attached stopper _E_. The piece _C_
falls and the opposite end _A_ holds _B_ suspended until the tank is
completely discharged.

[Illustration: FIG. 108.--Siphon-jet closet with low-down tank.]

[Illustration: FIG. 109.--Details of construction of low-down flush

The action of the tank shown in Fig. 110 is the same as the others
except that of the discharge mechanism. In the drawing, the tank is
full of water ready to be discharged when required. A hollow rubber
ball _E_ serves as a stopper for the discharge pipe. The ball is kept
in place, when the tank is filling, by the pressure of the water above
it. The discharge is started by pressing down the trip on the front of
the tank. This raises the ball from its seat, and being lighter than
water, it floats, thus leaving the discharge pipe open until the tank
is empty, when the ball is again back on its seat. As the tank fills
the pressure of the water above prevents the ball from again floating,
until lifted from its seat. The supply valve and refilling pipe _D_ is
the same in action as in the other tank.

[Illustration: FIG. 110.--Details of construction of the float-valve,
low-down flush tank.]

[Illustration: FIG. 111.--Method of using the plumber’s friend, in
removing obstructions.]

=Opening Stopped Pipes.=--It occasionally happens that pipes
leading from the various toilet fixtures become stopped because of
accumulations or by articles that accidentally pass the entrance.
In case the pipe has a trap connection the stoppage is most likely
to occur at that point. Usually the obstruction may be removed by
detaching the screw-plug of the trap and removing the accumulation with
a wire.

Closet seats furnish an inviting receptacle for waste material of
almost every kind. Stoppages are not uncommon and are generally found
in the trap. One method of removing obstruction is by use of the
plumbers’ friend. This device is shown at _P-R_, in Fig. 111. It
consists of a wooden handle _P_ attached to a cup-shaped rubber piece

The plumbers’ friend is shown in the figure, placed to remove an
obstruction _S_ that is lodged in the trap. A sudden downward thrust
causes the rubber cap _R_ to entirely fill the closet outlet and the
resulting pressure to the water is generally sufficient to force the
obstruction through the trap to the soil pipe.

[Illustration: FIG. 112.--Method of removing obstructions from a
stopped drain-pipe.]

The kitchen sink is another place that affords opportunity for
accumulation that stops the waste pipe. Accumulation of grease in the
trap is a common cause of trouble. This may be remedied to some extent
by the use of potash or caustic soda. When the pipe is stopped and the
trouble cannot be reached from the trap, a common method of removing
the stoppage is that suggested in Fig. 112. A piece of heavy rubber
tubing is forced over the water tap and the other end tightly wedged
into the drain pipe; the water is then turned on and generally the
pressure is sufficient to force the accumulation down the pipe.

=Sewer Gas.=--The prevalent fear of the deleterious effect of escaping
sewer gas is one that has been magnified to an unwarrantable degree.
Among bacteriologists it is very generally recognized that none of the
dreaded diseases to which the human kind is susceptible are transmitted
by gases. The one possible harmful effect recognized in sewer gas
by scientists is that produced by carbon monoxide. Sewer gas often
contains, from escaping illuminating gas, sufficient carbon monoxide
to produce the poisoning effect characteristic of that gas but the
possibility of danger is quite remote. The leakage of sewer gas is
detected by the sense of smell sooner than in almost any other way.
While leaks in sewer pipes are unhygienic in that they are conducive to
undesirable atmospheric conditions, they should not be looked upon as
the agents through which transmissible diseases are carried.

To the average person the term sewer gas conveys the impression of
a particularly loathsome form of vaporous contagion, capable of
distributing every form of communicable disease. To the scientific
mind it means no more than a bad odor. Sewer gas is really nothing but
ill-smelling air.


The hot-water supply to the household is of so much importance, that
the installation of the range boiler should be made with great care,
and an understanding of the principle on which it works should be fully
appreciated by all who have to do with its management. The ability of
the boiler to supply the demands put upon it depends in a great measure
on its size and the arrangement of its parts, but proper management is
necessary to assure a supply of hot water when required.

Range boilers are used for storing hot water heated by the _water-back_
of the kitchen range or other water heater, during a period when water
is not drawn. It serves as a reserve supply where the heater is not of
sufficient size to heat water as fast as is demanded.

As commonly used, range boilers are galvanized-steel tanks made
expressly for household use. They are standard in form and may be
bought of any dealer in plumbing or household supplies. In capacity
they range from 20 to 200 gallons and are made for either high-or
low-pressure service. They are said to be tested at the factory to a
pressure of 200 pounds to the square inch and are rated to stand a
working pressure of 150 pounds. Range boilers are galvanized after they
are made and coated both inside and out. The coating of zinc received
in the galvanizing process helps to make their seams tight and at the
same time renders the surface free from rust.

There is no definite means of determining the size of tank to be used
in any given case, because of the varying demands of a household but a
common practice is to allow 5 gallons in capacity to each person the
house is able to accommodate.

=The Water-back.=--The most common method of heating water for the
range boiler is by use of the _water-back_ or _water-front_ of the
kitchen range. The _water-back_ is a hollow cast-iron piece that is
made to take the place of the back fire-box lining of the range. In
some ranges the heater occupies the front of the fire-box instead of
the back, in which case the heater becomes the _water-front_.

The arrangement of pipes connecting the source of water supply with
the boiler is such that cold water is constantly supplied to the tank
as the hot water is drawn. If no water is drawn from the tank, it will
continue to circulate through the tank and heater, the water becoming
constantly hotter.

The connecting pipes are usually of iron but sometimes pipes of copper
or brass are used. The joints should be reamed to remove the burr that
is formed in cutting. The angles should be 45-degree bends or better
still 90-degree bends in connecting the heater with the tank so as to
cut down the amount of friction as much as possible.

[Illustration: FIG. 113.--A common method of connecting the range
boiler to the water-back.]

In Fig. 113 is shown a standard range boiler connected to the range.
The water is brought into the top of the tank through the pipe _a-a_,
and passing through it enters the water-back by means of the pipe
_b_. After passing through the water-back the water again enters the
tank through the pipes _c_ and _d_, as indicated by the arrow. The
_flow pipe_ (carrying the out-going water) from the water-back may
be connected with the tank at _e_, as shown dotted or in some cases
the connections are made at both places. The velocity of circulation
depends on the vertical height of the column of hot water and the
greater height will, therefore, improve the circulation and thus
increase the efficiency of the heater. The circulation of the water
through the tank and heater is produced by its change in weight as the
water is heated. As the hot water comes from the water-back it rises
in the pipe because it is lighter in weight than the cooler water of
the tank. In the case of the pipe shown dotted in Fig. 113 the longer
vertical rise will give a greater upward velocity of the hot water and
consequently a better circulation through the entire circuit.

The construction of the water-back is shown in the small drawing. The
connections are made at _b_ and _c_ as before. A division plate in the
water-back causes the water flowing in at _b_ to follow the length of
the heater at the bottom and return at the top as indicated by the
arrow, when it is discharged at _C_.

The hottest water is always at the top of the tank and the temperature
grades uniformly from the hottest at the top to the coolest at the
bottom. The reason for extending the pipe _a_ so far down into the tank
is that the cold water may not mingle with the hot water and reduce
its temperature on entering the tank. Near the top of the pipe _a_
is a small hole _f_ that is intended to prevent the water from being
siphoned from the tank in case a vacuum is formed in the cold-water
pipe. In this arrangement the water enters and leaves at the top of
the tank. In case the supply is shut off at any time the tank is left
almost full of water, because the siphoning effect cannot extend below
the small hole _f_.

=Excessive Pressure.=--Accidents due to the explosion of hot-water
backs are not at all rare and it should be borne in mind that there
is danger of excessive pressure being formed should the pipes _b_ and
_c_ become stopped. Under normal conditions the pressure generated by
the heated water is relieved by the water in the tank being forced
back into the supply pipe. The pressure in the tank, therefore, cannot
become greater than that of the source of supply, but if _b_ and _c_
should become stopped with the water-back full of water a dangerous
pressure might result. The greatest danger from this cause is that
of freezing. It frequently happens that houses are closed during
cold weather and the water-back is left undrained. The water freezes
and when a fire is started in the range, the ice in the water-back
is the first to melt. In a short time steam will be generated that
will soon produce a sufficient pressure to burst the water-back.
This has happened many times with disastrous results. Such dangers
may be avoided by the exercise of a reasonable amount of care in the
management of the range. To drain the water-back, the water is first
shut off at the point where the supply pipe enters the house. The
water in the range boiler is then drawn off by means of the cock _h_.

[Illustration: FIG. 114.--Blow-off for removing sediment.]

=Blow-off Cock.=--When a considerable amount of sediment is carried
in the water the range boiler acts as a settling tank and the deposit
accumulated at the bottom will in time amount to a source of trouble.
The accumulation is shown in Fig. 114. The part _W_, which connects
with _B_, is sometimes provided with a blow-off cock that will admit
of a discharge of the sediment. More commonly the piping is arranged
as shown in Fig. 113, when sediment is removed by occasionally drawing
water from the cock _h_.

[Illustration: FIG. 115.--Method of connecting the range boiler when
placed on the floor below the heater.]

=Location of Range Boiler.=--It is sometimes desired to place the
range boiler on a different floor, either above or below the range.
While such arrangements are entirely possible the circulation of the
water is not so good as that described above. The weight of the two
columns of water in the connecting pipes are so nearly balanced that
good circulation is not always possible. In Fig. 115 the connections
are shown, where the tank is located in the basement. In connecting the
water-back to the tank under such conditions the piping is relatively
the same as is shown in the dotted connections of Fig. 113, but the
connections are longer. The circulating pipe comes from the bottom of
the tank and leads to the bottom of the water-back. The flow pipe from
the top of the water-back is extended up to a distance equal or greater
than the distance from the water-back to the bottom of the tank. The
hot water is taken from the top of the flow pipe at any place above the

=Double Heater Connections.=--Two heaters are sometimes connected to
one range boiler, each circuit being independent of the other. Under
such conditions one or both heaters may be used. When the tank is
connected as shown in Fig. 116 the pipe _a_, from the bottom of the
tank, branches and leads to _b_ and _b´_, at the bottom of each of the
heaters. The flow pipes from the top of the heaters enter the tank at
separate places, the lower heater sending its water into the side of
the tank at _c_, and the upper heater flowing into the pipe _d_, at
the top of the tank. It would be perfectly possible to reverse the
connections for the flow pipes in the arrangement of Fig. 116 and
attain the same results. In such combinations the heaters are sometimes
piped tandem, the water flowing through each of the heaters in turn.
This, however, is not the best method to employ, for if only one of the
heaters is used the second acts to cool the water.

[Illustration: FIG. 116.--Double connections for the range boiler where
a heater is placed in the basement for occasional use.]

=Horizontal Range Boilers.=--It occasionally happens that in a small
kitchen there is no convenient floor space for the range boiler and
it becomes necessary to suspend it from the ceiling. It is perfectly
possible to station the ordinary range boiler in such a position and
have it work fairly well but from the location of the cold-water
inlet, only that part of the range boiler above the cold water pipe is
actually used for storage. The water in the lower half constantly mixes
with the entering cold water before it is heated by passing through the
water-back. When hot water is drawn from the top of the range boiler,
cold water enters by the cold-water pipe and reduces the temperature
of most of the lower half. Fig. 117 illustrates such an arrangement.
In this case the pipes connected with the water-back are those that
correspond to the circulating pipes _a_ and _e_ in Fig. 113.

Suppose the range boiler is full of water, and that it is being heated.
The lower pipe at the left-hand end is conducting the water to the
water-back and it is being returned to the range boiler by the upper
pipe at the same end. When the hot water is drawn from the top of the
range boiler by the _hot-water_ pipe, the entering cold water mixes
with hot water in most of the lower half of the range boiler before it
has been heated by passing through the water-back and so reduces the
temperature of most of the lower half of the tank.

[Illustration: FIG. 117.--Method of connecting the vertical
range-boiler in a horizontal position.]

[Illustration: FIG. 118.--Horizontal range-boiler suspended from the

A much better tank for the purpose is that indicated in Fig. 118. This
is a tank made particularly for such a location. The cold water enters
at the bottom of the tank and also leaves the bottom on its way to the
water-back. Circulation takes place through the water-back as before
but when hot water is drawn from the top of the tank, the entering cold
water at the bottom mixes with only that at the lower part of the tank
and so cools but a small amount of the hot water in storage. Hot-water
tanks of this kind are tapped for pipe connections in two places on
both the top and bottom sides and also at the ends as shown in the

=Tank Heaters.=--When the demand for hot water is sufficient to warrant
a separate hot-water heater the apparatus similar to Fig. 119 is used.
With such a heater, the conditions of overheated water--to be described
later--may be almost entirely avoided. In this case the connections are
arranged similarly to those of the range boiler but a separate furnace
takes the place of the water-back. The heater is simply a small furnace
made expressly for heating water. Connected with the discharge pipe _p_
is a draft-regulating valve which controls the drafts of the heater.
The draft-regulator is set to so control the furnace that water at the
desired temperature will always be in the tank. The mechanism of this
regulator is the same as the draft-regulator described under hot-water
heating plants.

=Overheated Water.=--Under ordinary conditions the water contained in
the range boiler is below the atmospheric boiling point (212°F.) but
at times when a hot fire is kept up in the range for a considerable
period, the temperature will rise to a degree much above that amount.
The temperature to which the water will rise will depend on the
pressure of the water supply. As an example--suppose the gage pressure
of the water supply is 25 pounds. The temperature corresponding to that
pressure is 258°F. The temperature of the water in the tank will rise
to that amount but not further because any additional temperature will
produce a higher pressure, but a higher pressure would be greater than
the pressure of the water supply and hence will back the water into the
supply pipe. This condition of things, then, acts as a safety valve to
the tank to prevent excessive pressures.

[Illustration: FIG. 119.--Independent hot-water heater with temperature

When the water at a high temperature is drawn from the tap a
considerable part of it will instantly vaporize, because of the
reduced pressure. If water at a pressure of 25 pounds is drawn from
the faucet, the temperature, 258°F., is sufficient to send all of the
water instantly into steam. This high temperature will scald at the
slightest touch. The water drawn from the faucet will continue to
vaporize as it comes into the air until the water in the tank is cooled
by the incoming cold water. The only means of relieving the overheated
condition is to open the faucet a slight amount and allow a portion of
the heated water to be drawn off.

It is evident from what has been said of the range boiler that it
operates under a variety of conditions. It is first a storage tank in
which is accumulated the water, heated from a greater or less period of
use of the range. Should the range fire be maintained through the day
or night the supply of hot water will be excessive and superheating is
the result. If the heater is to be used during short periods of time,
the piping should be arranged to produce the best circulation; on the
contrary, should the heater be used continuously--as in the case of a
furnace coil--a slow circulation through the tank is most to be desired
and the piping should be arranged for that purpose.

In the use of furnace heaters, superheating is likely to occur during
cold weather when a hot fire must be used over a long period of time.
In order to conserve the heat accumulated under such conditions a
hot-water radiator is frequently connected with the range boiler
through which to dispose of the excess heat. This radiator may be
placed in any desired position and so connected by a valve as to
discontinue its use at any time.

[Illustration: FIG. 120.--The range boiler connections when a furnace
coil is used for hot-water heating.]

=Furnace Hot-water Heaters.=--It is sometimes more convenient to use
the furnace as a means of heating water than the kitchen range. Such an
arrangement is shown in Fig. 120, where a loop of pipe in the fire-box
of the furnace takes the place of the water-back. The arrangement of
the pipes in the range boiler are as before, the water entering the
tank through the pipe _A_, circulates through the pipes _B_ and _C_,
receiving its heat while passing through the loop in the furnace, in
exactly the same way as in the water-back. It would be quite possible
to also connect the kitchen range with the tank as shown by the dotted
lines indicating the water-back. Such an arrangement would virtually be
that shown in Fig. 116, where the two heaters on different floors are
connected with the boiler.

=Instantaneous Heaters.=--In isolated bathrooms where no constant
supply of hot water is available, instantaneous hot-water heaters are
much used. In many houses where a range fire is used intermittently,
particularly during the summer months, a like method is used for the
hot-water supply. These heaters are made in many forms to suit any
condition. Some are very simple, being made of a gas heater, the heat
from which is held against a long coil of pipe or a large amount of
heating surface in other form, through which the water circulates on
its way to the tap. Others are quite elaborate, being made entirely
automatic in their action. The Ruud heater, for example, is so
constructed that when the hot-water faucet is opened the reduced water
pressure starts a gas heater in contact with a series of pipe coils
through which the water circulates. As soon as the water faucet is
closed the water pressure automatically closes the gas valve, cutting
off the supply of gas. A little gas jet used for igniting the burner is
left constantly burning, ready to light the gas whenever hot water is

Fig. 121 illustrates a simple form of instantaneous heater that is
relatively inexpensive and has met with a great deal of favor. A
sheet-iron casing encloses a sinuous, multiple coil of pipes through
which the water passes. The heat furnished by a Bunsen burner of a
large number of small jets is evenly distributed over the bottom of the
heater. The heating coils are arranged to interrupt the heat passing
through the casing and absorb as much as possible. To do good work such
a heater must be connected by a pipe to a chimney flue which furnishes
a good draught.

Instantaneous water heaters should not be used in bathrooms unless the
products of combustion from the heater are carried away by a chimney.
The combustion of the required amount of gas produces a large volume of
carbonic acid gas which if allowed to remain in the room is not only
deleterious but may be a positive danger to life. Cases of asphyxiation
from this cause are not at all rare.

[Illustration: FIG. 121.--Gas heater for hot-water supply.]

[Illustration: FIG. 122.--Hot-water supply with gas heater, connected
to the range boiler.]

Fig. 122 shows the heater connected with a range boiler. In this case
the heater may be considered as taking the place of the water-back. It
may, however, be used as an auxiliary heater. In the picture of the
kitchen shown in Fig. 80, an instantaneous heater is shown attached to
the range boiler. It is located in this case between the kitchen range
and the boiler.



The use of water enters into each detail of the affairs of everyday
life and forms a part of every article of food; its quality has much to
do with the health of the family, and its convenience of distribution
lends greatly to the contentment of its members. The family water
supply should be as carefully guarded as means will permit, and
judicious care should be exercised to prevent the possibility of its
pollution. Where the source of the water is known, it should be the
subject of unremitting attention.

Water comes originally from rain or snow and as it falls, it is pure.
Water, however, in falling through the air absorbs the contained vapors
and washes the air free from suspended organic matter in the form
of dust, so that when it reaches the earth rain water contains some

As the water is absorbed by the earth, it comes into contact with the
mineral matter and organic materials of animal and vegetable origin
contained in the soil; and as water is a most wonderful solvent, it
soon contains mineral salts and possibly the leachings from the organic
substances through which it passes. The impurities usually found in
well water are in the form of mineral salts that have been taken up
from the earth, but other contaminating materials may come from the
surface and be carried into the well by accidental drainage.

Water that is colorless and odorless is usually considered good for
drinking and in the absence of more accurate means of determination
may be used as a test of excellence; but it often happens that water
possessing these qualities is so heavily freighted with mineral salts
as to be the direct cause of impaired health. Again, water that appears
pure may be polluted with disease-producing bacteria to such an extent
as to endanger the lives of all who use it. The fact that a source of
drinking water bears a local reputation for purity, because of long
usage, cannot be taken as a test of its actual purity until it has been
subjected to chemical and bacterial examination.

It must not be inferred that all water is likely to be unsuitable for
drinking; there is, however, a possibility of the water being polluted
from natural sources and from accidental causes, that are sometimes
preventable; and the only means of determining the purity of water is
by chemical and bacterial examining.

=Water Analysis.=--In order to be assured as to the quality of drinking
water, it should be subjected to analysis and the result of the
analysis inspected by a physician of good standing. Such analysis may
usually be obtained free of charge from the State Board of Health and
if asked, the Chief Chemist will usually give his opinion regarding the
quality as drinking water.

In chemical water analysis, the total amount of solids, regardless of
their nature is taken as indicative of its excellence for drinking
purposes. These solids may be either in suspension and give the water a
color or produce a turbidity, or they may be entirely in solution and
the water appear colorless. English authorities on the subject place
the allowable proportion of solids at 500 parts to the million. Any
water that contains more than 500 parts to the million is condemned for
drinking purposes. Water containing 500 parts or less to the million is
considered good. The Standard of the American Board of Health permits
the use of water for city supply that contains 1000 parts of solid
matter to the million.

The amount of solids contained in water is not at all a definite
indication of its quality for drinking purposes, as may be inferred
from the widely varying amounts permitted by the different authorities,
but it gives an indication of its character because of the known
physiological action of the contained solids.

Chemical analysis alone cannot be taken as a complete indication of the
character of water, because such analysis shows nothing of the bacteria
that may be present. The organic matter may indicate the possible
presence of bacteria, but microscopic examination will be required to
determine its harmful properties.

As examples of the chemical constituents of potable waters, the
following furnish illustrations of different types of water in general

=Pokegama Water.=--The water from Pokegama Spring at Detroit, Minn. is
used widely through the Northwest as a table water. It is considered to
be a very excellent drinking water because of the low amount of solids
and the absence of any deleterious constituents. The complete chemical
analysis as reported by the North Dakota Pure Food Laboratory is as

                                                 Grains per gallon
    Sodium chloride                                    0.0200
    Sodium sulphate                                    0.0357
    Sodium carbonate                                   3.9288
    Calcium carbonate                                 11.3997
    Lime carbonate                                     0.0016
    Magnesium carbonate                                3.8896
    Sodium phosphate                                    trace
    Potassium sulphate                                 0.4435
    Silica                                             0.4416
    Organic matter                                     0.1006
      Total                                           20.2611

The total solids, 20.2611 grains per gallon, equivalent to 346.85 parts
per million, is very low and composed of carbonates of sodium, calcium
and magnesium, none of which are in any way harmful even in much larger
quantities. The amount of organic matter is practically nothing.

=River Water.=--The water supply of the city of Fargo, N. D., is taken
from the Red River of the North, which after being filtered through
a mechanical filtration plant is supplied to the water system of the
city. The river water in its raw state is considered unfit for drinking
because of the amount of organic matter present at different times of
the year.

Analysis of raw water from intake pipe, April 14, 1913:

                                               Parts per million
    Chlorine                                                  10
    Equivalent as sodium chloride, salt                       16
    Volatile and organic matter                       80
    Mineral solids                                   180
      Total solids                                   260

In this water neither the solids nor the organic matter are at all
high but during a part of each year there are many pathogenic germs
present, the contained typhoid bacillus being the most feared. The
following is an analysis after the water has been filtered, April 14,

                                              Parts per million
    Chlorine                                                 12
    Equivalent as sodium chloride, salt                      18
    Volatile and organic matter                      45
    Mineral solids                                  140
      Total solids                                  185

It will be noticed that in the process of filtration there has been
removed from the water 35 parts to the million of organic matter and
with probably 99 per cent. of the pathogenic bacteria. In addition
there has been removed 40 parts to the million of mineral solids, the
removal of which has changed a _very hard_ water to that which is
reasonably soft. The process of filtration has changed water that is
generally condemned for drinking to one that is considered remarkably

=Artesian Water.=--The analysis of the sample of artesian water given
below is an example of the water analysis made by the North Dakota Pure
Food Laboratory. It furnishes an illustration of the type of reports
that are returned from samples of water submitted for examination. This
report was in the form of a letter which was taken at random from the
files of the laboratory.

Sample of artesian water No. 1936 from Moorhead, Minn.:

                                                Parts per million
    Chlorine                                                   70
    Equivalent as sodium chloride, salt                       116
    Volatile and organic matter                        90
    Mineral solids                                    455
      Total solids                                    545

     “The solids in this water are made up of sodium chloride, salt,
     116 parts; volatile and organic matter, 90 parts; lime sulphate,
     a trace; lime carbonate, a slight amount; magnesium carbonate, a
     slight amount; and the balance of the solids are all wholly made
     up of sodium bicarbonate. This water is low in solids and of good

=Medical Water.=--The solids that occur most commonly in spring and
well water appear in the form of mineral salts. It frequently happens
that salts giving a cathartic action are present in sufficient quantity
to render the water objectionable when used for drinking. Sodium
chloride or common salt frequently occurs in quantity sufficient to
be distinctly noticeable. Magnesium sulphate (Epsom salts) and sodium
sulphate (Glauber salts), both of which are well-known laxative
salts, very commonly occur in well water. The carbonates of calcium
and sulphur also frequently found in well water are inert in physical
action when taken in drinking water. The presence of laxative salts in
spring water has given great celebrity to many springs both in Europe
and America that are famous as cures for all manner of human ills. Such
curative value as these springs possess is derived from the cathartic
salts contained by the water.

The table of contents of the Saratoga Congress Water as given by Dr.
Woods Hutchinson shows the solids of one of the most celebrated of
America’s medicinal waters.

                                                 Grains per gallon
    Sodium chloride                                  385
    Magnesium carbonate                               56
    Calcium carbonate and sulphate                   116
    Sodium bicarbonate                                 9
    Sodium iodide                                      4
    Bromide, iron, silica                           trace
      Total solids                                    570

When reduced to ordinary measure and given their common names the
mineral solids in a gallon of this water will be approximately:

    Common salt                                   8 teaspoonfuls
    Magnesium                                     1 teaspoonful
    Lime and plaster of Paris                     2 teaspoonfuls
    Baking soda                                 1/6 teaspoonful
    Bromides and iodides                       1/12 teaspoonful

The total solids, 570 grains per gallon, contained in Saratoga water,
gives the remarkably high content in total solids, of 9758 parts per
million; this is almost ten times the limit of the American standard.
While such water would not do for constant consumption, it is taken for
considerable periods of time with beneficial results and is recommended
by many authorities as a water of great medicinal potency.

While most medical authorities condemn the use of water high in
solids, the ideal drinking water is neither soft water nor distilled
water--that is, water that is perfectly free from any saltiness--but
one that contains a moderate amount of the ordinary constituents of
the earth. It is reasonably safe to assume that any unpolluted water
containing as high percentage of solids as 1000 parts of total solids
to the million, and that is agreeable to the taste, would be safe for

     “Chemical analysis in general indicates the possible pollution
     of water. A relatively high content of organic substances,
     nitrate, chlorides and sulphates, might indicate contamination,
     particularly when ammonia is also present. On the other hand, a
     high content of just one of the above-mentioned substances, be it
     organic, chloride, nitrate or sulphate, may originate from the
     natural soil strata.”

=Organic Matter.=--Organic matter may come from peat swamps, decaying
leaves and grasses; or it may come from decayed animal matter which
finds its way into the soil; or worst of all it may come from cesspools
or other sewage. While the presence of organic matter does not
necessarily indicate the presence of disease-producing bacteria, it is
a medium in which such germs live and multiply; for that reason it is
an indicator of possible harm.

     “Waters containing a high percentage of organic substances and
     among them products of putrefaction are frequently used without
     damage but they are capable of producing gastro-intestinal
     catarrh, phenomena of excitement and paralysis as well as death.
     Of the many pathogenic bacteria that sooner or later may get into
     the water, those of cholera and typhoid are of special importance.

     “Pathogenic bacteria occur but rarely and when once they find
     their way into a water, they generally do not multiply but remain
     for a greater or lesser period viable.

     “Bacteria enter wells by three different modes: first, from
     surface water that is washed from the soil by rain; second, from
     faulty construction of the curbing; and third, from bacteria
     entering the soil from vaults, etc.” (Van Es).

=Ammonia.=--In the analysis of water the presence of ammonia is an
indicator of organic matter. Ammonia is not of itself injurious but it
indicates the presence of matter in which bacteria find conditions
suited to their growth. Free ammonia is usually considered an indicator
of recent pollution, while albuminoid ammonia indicates the presence of
nitrogenous matter that has not undergone sufficient decomposition to
form ammonia compounds.

=Hardness in Water.=--Water that holds no mineral matter in solution
is “soft water” and when soap is added will readily form a lather. The
presence of lime or magnesia is commonly the cause of “hardness” in
water. Either of these minerals, when present form an insoluble curd
when the soap is added to the water and the soap will not form a lather
until enough soap has been added to unite with the mineral matter
present. The hardening agents are usually in the form of bicarbonates
and sulphates. All soap used in neutralizing the hardening agents is
wasted, because a lather will not form until all of the hardening
materials are neutralized. It is evident that the softening of water
for domestic purposes is beneficial, both because of the less amount of
soap required and because of the absence of the curd.

Hardness in water may occur in two forms--as temporary hardness or as
permanent hardness. When bicarbonate predominates as the hardening
agent, the water is said to be temporarily hard because, when heated
to boiling, the bicarbonate is precipitated and the water is thus
softened. When softening of such water is to be done on a large scale,
chemical treatment is more satisfactory. Water containing bicarbonate
of lime may be softened by adding a pound of lime to 1000 gallons or 1
pound of lime to 165 cubic feet of the water. This quantity of lime is
sufficient to remove 10 grains of the bicarbonate to the gallon.

When the mineral matter is in the form of sulphates, mainly sulphate
of lime or magnesia, the water is said to be permanently hard, because
boiling will not soften it. Such water may be softened by adding soda
ash or impure carbonate of soda. One pound to 1-1/4 pounds of “washing
soda” to each 1000 gallons of water will render such water soft; by
its action the sulphate of lime is precipitated and settles to the
bottom of the container; the water may then be siphoned off leaving the
precipitate in the bottom.

=Iron in Water.=--Water containing iron is found in many wells and
springs. While iron is not harmful, it is objectionable to taste
and stains most things with which it is long in contact. It may
be precipitated with lime and removed as the sulphate of magnesia
described in the preceding paragraph.

=Water Softening with Hydrated Silicates.=--By W. L. Stockham,
assistant chemist, North Dakota Experiment Station.

     “The use of chemicals in softening water requires the mechanical
     removal of the separated materials by skimming, settling or
     filtering and it is difficult to determine just how much chemical
     to add. A new process for softening water, and one that has
     awakened great interest because of its efficiency, employs
     hydrated silicates of aluminum or iron combined with soluble
     bases. This process softens water from practically any condition
     or hardness.

     “The form of apparatus in use varies from a portable jar, with an
     inlet at the top and an outlet at the bottom, to the more complex
     tanks for industrial and domestic purposes. A plant for domestic
     use might consist of a 20-gallon tank for containing the softening
     material and a second tank in which is prepared the salt solution
     for reactivating the softener. The two tanks with their valves
     and connections constitute the apparatus. The softener, supported
     by a porous plate, sieve, or layer of gravel, completely fills
     the first tank and the water to be treated passes through the
     interspaces between the granules. In some plants the water passes
     through a layer of marble chips before coming into contact with
     the softener. The apparatus may be attached temporarily to the
     faucet or connected permanently with the water system. A gravity
     system may be employed where the water pressure is lacking.

     “The softener is put on the market in granular form and may be
     purchased and used with apparatus other than that furnished by
     manufacturers. The granules are about 1/4 inch in diameter and
     permit a ready passage of the water through the interspaces. The
     material lasts indefinitely.

     “As the water passes through the apparatus, the large exposed
     surface of the granules entirely absorbs the calcium and
     magnesium, which produce hardness, making it soft and ready for
     immediate use. The water does not require being in contact with
     the softener any longer than the time taken to pass through and
     it emerges almost as fast as from the faucet. The softener must
     be reactivated after it has softened a certain amount of water.
     This is accomplished by filling the tank with a common salt
     solution which is contained in the second tank. The water supply
     is temporarily shut off and the salt solution allowed to fill the
     softening tank. After remaining in contact with the granules
     for a time the chemical action of the salt releases the calcium
     and magnesium, which are flushed out with the excess of salt
     solution, into the sewer. The softener thus renewed is ready for
     softening another supply of water. Since this renewal is a simple
     application of the law of mass action, an excess of the salt must
     be used. The renewal may be repeated indefinitely.

     “The amount of any particular sample of water which can be
     softened before renewal depends on the amount of material in the
     apparatus and the hardness of the water. Five gallons of the water
     per pound of softener would not be far from the average capacity.
     Where a large amount of soft water is required at one time, it may
     be prepared in advance and accumulated in a tank or cistern.

     “The cost of softening, aside from the original cost of the plant,
     is nominal, as the value of the salt solution is the only expense.

     “The water produced by this process is absolutely soft and
     suitable for drinking, domestic and industrial purposes. In the
     case of very hard water the saving in soap for washing is more
     than equal to the cost of operation. There are at least three
     firms manufacturing softening plants of the kind at the present
     time: The Permutite Co. of New York; the Cartright Co. of Chicago,
     whose product is called Borromite; and the Des Moines Refining
     Co., manufacturers of Refinite.

     “A comparative test of various forms of water-softening materials
     may be obtained from the Regulatory Department, North Dakota
     Agricultural College.”

=Chlorine.=--The presence of chlorine in water may indicate the
presence of polluting matter in the form of sewage but only when the
amount is considerably above the normal amount of chlorine that is
contained in the soil in the community from which the water is taken.
An increase of the chlorine in the water would indicate a probable
pollution from sewage.

=Polluted Water.=--Well water that is roily or that possesses
objectionable taste or odor may be suspected of containing polluting
matter and should be boiled before being used for drinking purposes
until such time as may be required to have it examined. Sickness due
to the use of polluted water does not necessarily develop as specific
diseases, unless the water contains disease-producing bacteria. Typhoid
fever, one of the commonest and most dreaded of diseases, is usually
transmitted by water. Typhoid is a disease of human origin, the germ
of which develops in the alimentary tract of the human kind alone. The
germs may be spread by the waste from the typhoid patient by being
thrown on the ground where it is taken up by the water and passes into
streams or it may enter wells from privies or cesspools. A single case
of typhoid has been known to so pollute the water of a stream, as to
produce an epidemic of the disease throughout the entire length of
the stream, among the people who drank its water; while water from a
polluted well often transmits disease to a neighborhood.

[Illustration: FIG. 123.--Some of the common causes of pollution of
wells, and the means of transmitting disease, such as typhoid, etc.]

=Pollution of Wells.=--The water from wells is often polluted by
seepage through the earth from sources that might be prevented. Fig.
123 illustrates some of the commonest sources of contamination that
through carelessness or ignorance are located in the neighborhood of
the family water supply. The drainage from such sources of pollution is
often directed toward the well and many cases of ill-health, disease
or death are the direct consequences of drinking its water. It may be
readily observed, in the case of the well illustrated, that the more
water that is pumped from the well, the greater will be the tendency of
the water from each of the sources of pollution to reach the well.

Another common cause of contamination of well water is that of
imperfect well curbs that allow the waste water or surface water to
flow into the well. The area about the well should be graded to allow
no standing water, and the waste should be conducted away without
permitting it to collect in standing pools.

Drainage from manured fields or other places where disintegrating
animal or vegetable matter may be absorbed by water is often the cause
of temporary pollution, where the water is carried to low-lying wells.
Wells located in low areas that receive the drainage from such places
may be suspected of pollution during the spring or early summer, when
during the remainder of the year the water is pure.

In connection with any water suspected of pollution, it is well to
remember that by boiling the water used for drinking, its harmful
properties are entirely destroyed.

=Safe Distance in the Location of Wells.=--In the location of a well,
the distance of safety from sources of pollution will depend, in a
considerable measure, on the character of the soil and the quantity
and concentration of the pollution material entering the ground water.
When coming from the surface, the danger is usually neither great nor
difficult to avoid; but when cesspools and privies in the neighborhood
are sunk to a considerable depth in porous earth, from which the supply
of water is drawn, the polluting material may reach the well undiluted.
No absolute radius of safety can be given, but certain generalizations
as to conditions may be made as to character of soil and the different
topographical conditions which surround a safe location.

In ordinary clay, or in clay mixed with pebbles and in soils of the
same general nature, through which the water circulates by seepage, the
pollution is not likely to be carried to a distance of 100 feet. Clay
offers marked resistance to the passage of water, which in beds of 3 to
5 feet thick will act as protection from pollution from above. In sandy
soils the movement of water is faster than in clayey soils, but 150
feet may be taken as a safe distance, unless the downward slope of the
land carries the polluting material directly to the well.

=Surface Pollution of Wells.=--In dug wells, pollution from the surface
is due most commonly to careless construction and lack of care. In Fig.
124 is indicated the most common cause of surface pollution. The figure
represents a well that has been curbed with planks. Through lack of
care the earth has sunken at the top, permitting the surface water to
flow into the well. The top of the well is on a level with the surface
and covered with loosely laid boards which allow the waste water to
drip through the joints. Such a well, even though the source of supply
is good, will likely yield water of inferior quality.

In bored wells, polluting water may enter through the uncemented joints
of the tiling or through the joints in the staves of wooden tubing; in
drilled or driven wells, through leaky joints or holes eaten in the
iron casing by corrosive waters. By cementing the interior surface of
stone-or brick-curbed wells, by replacing wood with cement or other
impervious curbs and by substituting new pipes for leaky iron casings,
the entrance of polluting water may be prevented.

In the average home the water supply is most commonly taken from
a well, the water from which comes through the earth from unknown
sources, and the character of chemical salts or organic matter the
water contains will depend on the kind of soil through which it passes
before reaching the well.

The water from wells, whether deep or shallow, is generally of
relatively local origin, it being absorbed by the soil and carried to
the water stratum by percolation. If the soil contains soluble mineral
salts the water will contain these materials in quantities depending
on the amount of the salts present in the earth. If the earth contains
organic matter as pathogenic bacteria the water is likely to contain
these bacteria in like numbers as they are present in the soil through
which the water filters.

[Illustration: FIG. 124.--Undesirable form of well curbing.]

As usually encountered, the water-bearing earth occurs in sheets rather
than in veins or streams. The movement of the water in such areas
follows the contour of the earth and is influenced by the varying
amount of rain or snowfall and the atmospheric pressure. The lateral
movement is often only a few inches a day and in some places no lateral
movement occurs at all. Underground streams of any kind are not usually
found except in limestone regions.

As a rule, a well is formed by digging or boring into the earth until
a stratum of water-bearing soil is encountered, the type of the well
being determined by the character of the earth and the location of
the water-bearing soil. The water from the surrounding area fills the
opening to the height of the saturated soil. As the water is pumped
from the well it is replenished by the flow from the surrounding earth.
If the soil is porous, as in the case of gravel, the water will refill
the well almost as fast as it is taken away by the pump. If the soil is
dense and the inward flow is slow, the well when once exhausted may be
a long time in refilling.

=Water Table.=--The upper level of the saturated portion of the soil
is known as the water table. It has a definite surface that conforms
to the broader surface irregularities. While a definite, determinable
water table appears only in porous soil, it exists even in dense rocks.
It rises and falls in wet seasons and in drought. In exceptionally
wet seasons the water table may be at or above the surface. Under
such conditions the opportunities for the pollution of wells is much
increased. In particularly dry seasons the water table may sink below
the bottom of the well, when it is said to “go dry.” The water table
follows the surface contour in a manner depending on the character of
the soil. It is flattest in sand or gravel areas but in clay it follows
the contour of deep slopes with but slight variation.

=The Devining Rod.=--The use of the devining rod, for the purpose of
locating suitable sites for wells, has been supposed by many to be a
gift possessed by a chosen few. The devining rod is a forked branch
of witch hazel, peach or other wood, which when held in the hands and
carried over the ground, is supposed to indicate the presence of water
by bending toward it.

In most cases the operators are entirely honest in their belief and
in a large proportion of trial their efforts have been successful
in locating desirable wells; but it has many times been proven that
the movement of the rod is due to an unconscious muscular movement
of the arms and hands, in places where the operator has previously
suspected the presence of water. The operator of the devining rods is
most successful in regions where water occurs in sheets, such as often
occur in gravel or pebbly clay. The successful use of the devining rod
cannot be explained by any scientific reasons. There have been invented
a number of devining rods, claimed by their inventors to be based on
scientific laws; but the government has not yet granted patents to
appliances of the kind.

=Selection of a Type of Well.=--The chief factor which controls the
selection of a type of well is the nature of the water-bearing earth,
the amount of water required, the cost of construction and the care of
the resulting supply.

If a large amount of water is to be demanded of a well, to be dug in
soil through which the water percolates slowly, the well must be large
in diameter, in order that the necessary supply may be accumulated. If
the earth is porous and yields its water readily, a small iron pipe
driven into the ground may supply the desired amount.

The character of the water-bearing material is of the greatest
importance in determining the yield of the well. In quicksand, water
is usually present in ample quantities, yet owing to the extremely
fine particles of which the quicksand is composed, its presence as a
water-bearing soil is highly undesirable.

=Flowing Wells.=--Flowing wells are obtained in places where water is
confined in the earth, under sufficient pressure to lift it to the
surface, through an opening made to the water-bearing stratum. These
are known as artesian wells, from the fact that they were first used
in Artois (anciently called Artesium) in France. In order that water
may have sufficient head to lift it to the surface, it must be confined
under impervious clay or other bed of earth, and with its source at a
level considerably higher than its point of exit. The source of supply
for flowing wells is often at a great distance. Because of the fact
that flowing wells are shut off from the surface by an impervious layer
of earth, the possibility of pollution from the surface is effectively
prevented. Any contamination of the water must come from a distance
and enter the water at its source. As pollution rarely extends through
the ground to any great lateral distance, artesian waters are seldom
polluted. The water from artesian wells often is heavy with mineral
matter and in many cases is unfit for drinking on that account.


Wells are constructed by different methods, depending on the character
of the soil in which they are sunk. Their excavation is usually
accomplished by one of three general methods: by digging; by driving a
pipe into the earth until it penetrates the water-bearing stratum; or
by boring a hole with an enlarged earth auger, into the water-bearing
soil. Artesian wells are made by drilling with a device suitable for
making a small and very deep hole.

=Dug Wells.=--In shallow wells the water seeps through the soil from
local precipitation. Deep wells are those from which the water is
brought to the surface through an impervious geologic formation, as
a bed of clay or rock, and from a depth greater than that from which
water may be lifted by atmospheric pressure. The fact that a deep
well originates from a source that entirely differs from that of the
shallow well accounts for the difference in chemical composition which
frequently exists in the water from the two types of wells in the same

The form of the dug well is generally that of a cylindrical shaft 4
feet or more in diameter and of depth depending on the location of
the water-bearing stratum. Where the character of the soil is such
that the seepage is slow and the water does not flow into the well as
fast as the pump will remove it, the well must contain a considerable
volume to supply the period of greatest demand. Wells of this kind are
commonly walled with brick or stone to keep the sides in place and to
prevent the entrance of surface waters. The top of this curb should be
brought above the surface of the ground and should be made water-tight
to prevent the entrance of surface waters. The space around the curb,
at the surface, should be graded to drain the water away from the well.
There should be no chance for the water to collect in pools about the
well; it should be conducted away in a gutter to the place of final
disposal. The well should be covered with a platform of concrete or
planking which will allow no water to enter from the surface.

Wells of this order are sometimes dug to great depth before the
water-bearing stratum is encountered; this may sometimes be reached
only after a great amount of expense and labor. The historic Joseph
Well, near Cairo, Egypt, is an open shaft, 18 by 24 feet in area, sunk
through solid rock 160 feet.

=Open Wells.=--Open wells have long been condemned as insanitary. The
familiar open well of the “Old Oaken Bucket” type is an inviting
receptacle for the deposit of all manner of refuse, which once inside
remains until it is disintegrated. These wells become the final resting
place of many small animals and all manner of creeping things, in
search of water. The open top receives wind-blown matter in the form of
leaves and dust, much of which is in the nature of polluting material.

[Illustration: FIG. 125.--Ideal form of well curbing with cover and
drain made of concrete.]

=The Ideal Well.=--In the case of a well which yields pure water, every
precaution should be taken to prevent its pollution. The ideal form
of construction is that shown in Fig. 125. In this well, the curbing
_C_ is of heavy concrete that extends above the natural surface of
the ground, to prevent the entrance of surface water, and that from
seepage through the upper stratum of the soil. The reinforced-concrete
top forms a close joint with the curb to prevent the entrance of
waste water and all animal life. The pump is of iron, secured to the
well cover by bolts, set in the concrete. The trough of concrete _G_
conducts the waste water from the well to a safe distance. The earth
about the well is so graded as to permit no water to stand in pools.

=Coverings of Concrete.=--The use of concrete for the coverings of
wells, cisterns and springs has become a recognized form of the best
construction. It is not more expensive than other good materials and
when properly executed it forms an imperishable protection and gives a
neat appearance. The spring cover in Fig. 126, and the cistern top in
Fig. 127 are illustrations of its application.

=Artesian Wells.=--Artesian wells are made by boring into the earth
until the drill reaches the artesian stratum, the internal pressure
forces the water through the opening to the surface. They are usually
small in diameter and often of great depth. In some areas the artesian
flow is found a few feet below the surface, but generally it is much
deeper and 3000 feet is not an unusual depth.

The pressure and amount of flow from these wells is sometimes
sufficient to permit the water being used for the generation of power.
Small waterwheels are not uncommonly driven in this way and the power
used for the generation of electricity for lighting and running small
household appliances.

=Driven Wells.=--In localities where the nature of the soil gives
opportunity, wells are made by driving a pipe to the required
depth. Wells of this character are usually made in places where the
water-bearing soil is of sand or gravel. The pipe terminates in a
sand-point such as that of Fig. 128. This sand-point is a perforated
pipe with a pointed end, that facilitates driving. The perforations, as
shown in the point _P_, form a strainer which allows the water to enter
the pipe but prevents the sand from filling the opening.

[Illustration: FIG. 126.--Concrete cover for a spring.]

[Illustration: FIG. 127.--Concrete cistern top.]

In the use of driven wells, the water-bearing soil must be sufficiently
open to allow the water to flow into the pipe as fast as the pump takes
it away.

=Bored Wells.=--In many localities the water-bearing stratum is of
such nature as to give a ready flow of water but yet not sufficient
to permit of the use of a sand-strainer; if, however, the opening is
somewhat enlarged, the water will enter with sufficient rapidity to
supply a pump. In such cases bored wells are quite generally used. They
are made by boring a hole of the required size with an earth auger.
These wells are made of any size up to 2 feet in diameter. They are
often called tubular wells because they are lined with iron tubing or
tile, to prevent the earth from refilling the hole.

[Illustration: FIG. 128.--Driven well with a sand-point strainer.]

=Cleaning of Wells.=--Very few dug wells are so constructed as to
exclude dust and washings from the ground. It is, therefore, necessary
that they be occasionally cleaned. Accumulations from these causes may
be sufficient to hinder the entrance of the water to the well and thus
lessen its capacity.

=Gases in Wells.=--One of the commonest gases found in wells is carbon
dioxide (carbonic acid gas). It may be detected by lowering a lighted
candle or lantern to the bottom. If the gas is present in dangerous
quantity, the flame will be extinguished. Death from asphyxiation
due to this gas is not an uncommon occurrence, to persons descending
into wells. Before entering a well, the test described above should
be applied, as a precaution against accident. Carbon dioxide is a
colorless, odorless gas in which a person will drown as readily as in

=Peculiarities of Wells.=--Owing to the formation of the water-bearing
earths, from which they receive their water, many wells possess marked
peculiarities of behavior that often give rise to local reputation
because of their vagaries. These characteristics have been classified
into breathing wells, blowing wells, sucking wells, etc. These effects
are in almost every case due to variation of barometric pressure. The
ordinary level of the water in a well is governed by the variation of
rainfall, melting of snow or the release of water by the thawing of
frozen ground. It often occurs, however, that the head of water is
markedly influenced by storms, when a rise of the level of the water
occurs at the time of low barometric pressure during the storm period.
This effect is often noticed in flowing wells. Many wells, at the
approach of storms, yield roily water to such an extent that where the
water is normally clear it may become for a period entirely unfit to
drink, because of the matter held in suspension. All of these effects
are accounted for by the varying atmospheric pressure. At the time of
high barometer, a well that ordinarily flows freely will have to be
pumped, the additional pressure of the air holding back the water to an
extent representing several feet of head. The change of an inch in the
barometric pressure will produce slightly more than a foot in head of
water. At the time of storms, the barometer is sometimes abnormally low
which will produce a corresponding rise of water in the well. At such
time the free flow of water into a dug well, from the usual source of
supply, will cause such a rapid flow of water through the passages in
the earth as to carry with the water the sediment that produces roily
water in the well. This sediment will settle after a while and the
water will again be clear.

=Breathing Well.=--Wells of this kind are most common in areas where
the water-bearing earth is of rock formation; particularly in limestone
areas, where caves and cavities are common. It sometimes happens that
in the neighborhood of a well there is a cavity in the earth of
considerable volume, the only entrance to which is through the well and
that being under usual conditions covered by water, a foot or more in
depth. With such a formation the conditions are right for a breathing
well. At times of high barometer the water is depressed and the air
will flow into the cavity through the well, when the well is said to
inhale. This inward flow of air will continue until the air pressure
in the cavity is equal to that of the outer air; and if the cavity is
large and the opening small, the inward flow of air may continue for
hours, even for days. With a fall of barometric pressure, the air in
the cavity, being at a higher pressure than the external air, the air
will flow outward and the well is said to exhale.

=Freezing Wells.=--In cold climates, particularly in territory
possessing cavernous limestone deposits, breathing wells often freeze
in winter. When large volumes of frigid air are drawn into a well, the
amount of heat taken from the water is sufficient to freeze it, and
stop the supply of water. This effect is sometimes remedied by plugging
the well at the top, so that the influx of cold air is prevented and
the water does not freeze.


Pumps for lifting and elevating water are made of both wood and iron
in almost endless variety; but for domestic purposes they are of
two general types--the lift pump and the force pump--which include
features that are common to all. The lift pump is intended for use in
lifting water from low-head cisterns and wells, the depth of which
is not beyond the head furnished by atmospheric pressure. The force
pump performs the work of a lift pump and in addition forces the water
from the outlet at a pressure to suit any domestic application. These
pumps are made by manufacturers in a great variety of forms, but
the essential parts are the same in all pumps intended for a single
purpose. The principle of operation is the same in all pumps of any
type. The difference in mechanism of pumps intended for the same
purpose is only in the form and arrangement of the parts.

=The Lift Pump.=--The kitchen pump is an example of the lift pump. It
is universally used for household purposes where water is to be raised
from cisterns, etc., and is most commonly made throughout of cast
iron. Fig. 129 illustrates one form, sometimes called the pitcher pump,
because of the slight resemblance to the article. It frequently carries
the name cistern pump from the fact that it very generally is used to
lift water from cisterns.

Although water may be raised 34 feet with a theoretically perfect pump
and with a barometric pressure of 30 inches the actual limit is much
lower. In use, 20 feet is probably about the limit and 10 feet or
less is that of common practice. A pump that requires “priming” would
raise water 15 feet with considerable difficulty for reasons that will
appear later. In Fig. 129 is shown a sectional view of the working
parts of the kitchen pump, the action and general form of which apply
to any lift pump. The body of the pump contains a cylinder, in which
closely fits a piston _P_, containing a valve _A_. At the bottom of
the cylinder is an additional valve _B_. The piston and two valves
constitute the working parts of the pump. The water is lifted through
the pipe _S_, and is discharged at _D_.

[Illustration: FIG. 129.--Sectional drawing of the kitchen pump showing
its working parts.]

The action of the pump is as follows: With the piston at the bottom
of the cylinders and with no water in the pump, the handle is forced
down, which action raised the piston. In so doing the air below it is
rarefied. The reduction of pressure due to the rarefication of the
air allows the water to rise in the pipe _S_ correspondingly. After
repeated strokes of the piston, the water reaches the valve _B_, which
raises to let it pass, but immediately closes at the end of the upward
stroke. When the space between the piston and the valve _B_ is filled
with water, each descent of the piston forces the water through the
valve _A_; and when the piston is raised, the water is lifted out
through the spout.

The valve _A_ is a loose piece of cast iron, surfaced on the lower side
to make good contact with the piston. The valve _B_ is of cast iron
fastened to a piece of leather by a screw. The leather makes a joint
with the valve-seat and furnishes an excellent valve for its use. In
order to keep the plunger _P_ tight in the cylinder, it is surrounded
with a leather gasket. Should this gasket become worn, as it will in
time, the plunger fits loosely in the cylinder and the pump will lift
the water with difficulty, because of the leakage around the gasket.
Should the valve _B_ leak, the water will gradually run back into the
pipe _S_, and the pump when left idle will lose its “priming.” The
plunger and the valve _B_ are the parts most likely to get out of
order. If the gasket around the piston _P_ is very much worn, and there
is no water in cylinder, the pump will require priming before the water
can be raised. If the pump contains no water and is left standing for a
considerable time, the leather parts of the valve dry out and shrink;
when the pump is again put into use, the valves will fail to work
properly, until the leathers are again water-soaked. Water is poured
into the top of the pump until the cylinder is filled, and as soon as
the leather becomes water-soaked and fills the cylinder, the piston
will again perform its function.

[Illustration: FIG. 130.--Method of attaching the house pump to kitchen

[Illustration: FIG. 131.--Sectional drawing of the force pump showing
its working parts.]

=The Force Pump.=--The house force pump is often used in place of the
ordinary lift pump, when no other means is at hand for providing water
under pressure. It furnishes a limited means for lawn sprinkling and
gives some degree of fire protection in isolated places. It may be
made a part of the kitchen sink as shown in Fig. 130, by use of the
attachment that appears in detail under the sink. This type of pump may
be used in small water-supply plants, such as that of Fig. 143; or in
connection with small pressure tanks for the same purpose. It differs
somewhat in construction from the lift pump, in that it has no valve in
the piston and is provided with a check valve and an air chamber for
generating pressure to the discharged water.

Fig. 131 shows the essential parts of the force pump and furnishes a
means of describing its operation. All force pumps possess the same
parts and the operation described applies with equal force to all. A
valve _A_ is located in the bottom of the cylinder and the check valve
_B_ prevents the return of the water to the cylinder after it has been
forced out of the pump. The action of the pump in raising the water
is the same as in the lift pump but when the water fills the cylinder
and the piston descends, the water is forced through the valve _B_ and
out at _D_. If the outlet pipe is slightly smaller than the opening in
the valve _B_, some of the water will enter the air chamber _C_ and
compress the air. The pressure thus generated will immediately tend to
force the water out and in course of ordinary pumping will send out
a steady stream instead of the intermittent flow of the lift pump.
Without the air chamber, the flow from this pump will be a series of
pulsations that attain maximum force with each descent of the piston.

[Illustration: FIG. 132.--Tank pump, commonly used in small domestic
water supply plants.]

=Tank Pump.=--The type of pump used with a water-supply plant will
depend entirely on the amount of water that is used. If the supply of
water to be provided is for only one or two people the house force pump
such as that of Fig. 130 will suffice; but when a greater number of
people are to be supplied, a force pump of the type shown in Fig. 132
is quite generally used. These pumps are made in a variety of patterns
and are commonly termed tank pumps. The one shown in the Fig. 132 is a
double-acting force pump in that the cylinder receives and discharges
water at each stroke of the piston. The air chamber is located at
_A_. Directly beneath the air chamber is the valve chest in which are
located the valves which regulate the entrance and discharge of the
water. As used in the average domestic plant the cylinders are 3 or 4
inches in diameter.


The pumps intended for raising water from wells are practically the
same in construction as the house pump, except that they are intended
to deliver a greater volume of water and sometimes to work under a
different condition, as that of the deep well pump. Well pumps have,
therefore, assumed certain standard forms that differ only in the
styles of mechanism employed by different manufacturers.

The one shown in Fig. 133 furnishes a good example of a general-purpose
iron pump which may be used either as a force pump or a lift pump. It
represents also the general construction of a deep-well pump, where the
water must be lifted from a level, below that at which a lift pump will

The piston and valves are enclosed in the cylinder _C_, placed below
the surface of the water in the well. This cylinder also appears in
section in the small drawing, showing the details of the valve. The
operation of this pump is identical to that of the lift pump already
described, but the addition of an air chamber gives it the necessary
facility to produce a continuous flow of water. In order to prevent
the air in the air chamber from escaping, the pump rod is surrounded
with the necessary stuffing-box which is usually packed with candle
wicking to assure a good joint. In deep wells the tube is elongated
sufficiently to place the cylinder _C_ below the surface of the water
in the well. Such pumps are operated either by hand or by power.

=Wooden Pump.=--The wooden pump of Fig. 134 furnishes a good
illustration of a type that was formerly used in great numbers. It is
an inexpensive and efficient pump made almost entirely of wood except
the cylinder which is quite generally made of iron, lined with enamel.
The valve and the piston with its valves are made of wood, but faced
with leather to insure tight joints. The piston is also provided with
leather packing to make it tight in the cylinder. The action of the
pump is the same as that already described. The wooden tube is made in
sections joined together by taper joints that are driven into place.

[Illustration: FIG. 133.--Sectional view of a well with an iron
cylinder pump, placed for deep-well pumping.]

[Illustration: FIG. 134.--Sectional view of a well and wooden pump for
shallow pumping.]

The piece at the side of the pump is provided to drain the water from
above the piston, as a precaution against freezing during extremely
cold weather. The rod, when raised, opens an orifice that leads to the
inside of the pump and permits the water to drain into the well.

=Pumps for Driven Wells.=--The method of constructing driven
wells--that of driving a pipe into the earth to the water-bearing
stratum of sand or gravel--requires a special end to prevent the pump
tube from becoming stopped. In order that the fine material may not
enter and fill the lower end of the tube, a sand-point is used, such
as that shown in Fig. 128. It is made of perforated brass tubing and
provided with a sharpened end to facilitate driving. The perforations
act as a strainer that keeps out all but the fine particles which will
pass the pump valves. Sand-points are made with strainers of various
degrees of fineness to suit the different conditions of soils. These
strainers may in the course of time become filled with particles of the
soil that lodge in the perforations and the outside become so encrusted
as to prevent the entrance of the water. In such case, the pipe must be
pulled out of the ground and the point replaced by a new one. In Fig.
128 is shown a driven well with the sand-point in the water-bearing
stratum. If the small particles of earth clog the strainer the pump
will “work hard” and yield only a portion of the water the soil is
capable of giving when the strainer is clear.

=Deep-well Pumps.=--The principle of operation as described in the
lift pump takes advantage of the atmospheric pressure to lift the
water above the first valve. The limiting distance to which water can
be lifted by the atmospheric pressure will depend on the altitude and
the atmospheric pressure. With the normal atmospheric pressure at sea
level, water can be lifted, theoretically, 34 feet, but in practice
the limiting value is never even approximated. The pump is usually
placed within 10 of 12 feet of the water and 20 feet is about the limit
of distance. The reason for this is because of the impossibility of
keeping the joints tight in the valve and tubing.

Where water is to be raised from a deep well, the cylinder with its
piston is placed near the water and the tube and rod, as that of Fig.
133, connects the cylinder with the pump stock. After the water has
passed the valve in the piston, it may be readily lifted to the pump
stock. In this way water is raised from wells of great depth.

=Tubular-well Cylinders.=--Tubular wells that are cased with iron
pipe are provided with a special type of pump cylinder that admits
of deep-well operation. The casing of the well being in place, the
cylinder shown in Fig. 135 is forced down the casing to its proper
place, the spring _S_ holding it in place until it is firmly secured. A
special seating tool is now lowered into the casing and attaches at _T_
to the coupling; as the tool is turned, rubber packing _R_ is expanded,
locking the cylinder firmly to the casing. This makes a complete pump
cylinder, which with the piston _P_ in place is operated as any other

[Illustration: FIG. 135.]

=Chain Pumps.=--In shallow wells and other sources of supply, where
water is to be lifted only a short distance, chain pumps have been used
to a great extent, because of their quick action. This pump, as shown
in Fig. 136, elevates the water by an endless chain being drawn through
the tube, the lower end of which is below the surface of the water.
The chain is provided at intervals with discs or rubber or iron, that
fit the bore of the tube and form pistons which elevate the water as
they ascend. The chain passes around a wheel in the upper part of the
box and is worked by the crank. Chain pumps are not usually employed
to elevate water a greater height than 20 feet. They are not efficient
pumps and are not sanitary because of the opportunity they give for
admitting polluting material to the well. Their one advantage is that
of quick action in elevating water short distances.

[Illustration: FIG. 136.--Chain pump often used in shallow wells.]


Cisterns for the storage of rain water have been used from the time
immemorial and are constructed in a great variety of forms. For
household use they are often made in the form of wooden or metal tanks,
either elevated or placed in the basement; the greater number, however,
are of the underground variety made of brick or concrete.

Wooden cisterns are made by manufacturers in different sizes and
shipped to the user “knocked down;” that is, they are taken apart and
the staves, bottom and hoops are shipped, packed in small space to save
space in transportation. Under some conditions they give good service
but are apt to leak at times and require attention on that account. In
damp basements they give out the disagreeable odor of damp wood.

Tanks made of galvanized iron are much used as cisterns for temporary
use. They are inexpensive and give good service but are short-lived.
Possibility of leakage is their greatest disadvantage. Underground
cisterns are built either in the basement or outside the house. They
are quite generally made jug-shaped, but are often constructed of
concrete in square and rectangular form. When built of brick the walls
are often made of a single course, but walls made of two courses of
brick are considered better practice. The walls and floor are made
water-tight by plastering with an inch or more of cement mortar.

When cisterns are made of concrete, the floor should be put in 6 inches
in depth and as soon after as possible the walls are put up. In good
construction the walls are 8 inches in thickness of concrete, made of
1 part good Portland cement, 2 parts clean sand and 4 parts crushed
stone. If the cistern is square or rectangular in form the walls should
be reinforced with woven wire or steel rods, to prevent cracking.

The curb of the cistern should extend above the surface of the ground
sufficiently to prevent surface water from entering, and the top should
be covered with a wood-lined sheet-metal cover to prevent freezing.

=Filters.=--Unfiltered cistern water is not, as a rule, fit for
drinking purposes because of pollution from dust and impurities washed
from the roof, but for bathing and laundry work filtered rain water is
greatly to be desired.

As rain water comes from the roofs of buildings, there is washed into
the cistern a considerable quantity of dust, leaves, bird droppings and
other polluting materials which contaminate and discolor the water.
This foreign matter is not injurious for the purposes intended, but to
render the water clear it should be filtered before using.

Filters for cisterns are quite generally made of soft brick laid in
cement mortar, the face of the brick being left uncovered. Fig. 137
illustrates a simple and efficient form of filter made of a single
course of brick. A space one-fourth to one-third of the volume of the
cistern is left for the filtered water. The opening at the top of
the wall must be large enough to admit a man, for some sediment will
collect even in the filtered water and the filter must be occasionally

[Illustration: FIG. 137.--Cross-section of a brick curbed cistern with
a brick filter wall.]

[Illustration: FIG. 138.--Cross-section of a concrete cistern with a
brick dome filter.]

The filter shown in Fig. 138 is dome-shaped and built of brick. The
water is pumped from inside the filter and the suction of pumping
filters the water as it is used. In this case the filtering action is
accelerated by reason of the reduced pressure inside the filter as the
water is pumped. The chief disadvantage in this form of filter is the
small area exposed for the filtering action and the relatively greater
amount of work required for pumping the water, due to the partial
vacuum formed as the water is pumped.

The cistern in Fig. 139 is provided with a catch basin which acts as
a strainer for removing leaves, etc., that would stain the water. It
is made in the form of a concrete basin and partly filled with gravel.
The filter in this case is formed by a depression in the cistern floor.
A section of tile is placed on the floor, and around it is filled
the filtering material of gravel and sand. Filters of this kind are
often filled with charcoal or other materials that are expected to
purify the water. They are usually inefficient because their value as
absorbers of polluting agents is short-lived and unless the materials
are frequently renewed they are valueless and sometimes a detriment to
rapid filtration.

[Illustration: FIG. 139.--Cross-section of a concrete cistern,
containing a sand filter.]


In places where its use is possible, the hydraulic ram is a most
convenient and inexpensive means of mechanical water supply. It is
simple in construction, requires very little attention and its cost of
operation is only the labor necessary to keep it in repair. Whenever
a sufficient supply of water will admit of a fall of a few feet, the
hydraulic ram may be used as a pump for forcing the water to a distant
elevated point, where it may be utilized for all domestic purposes.
The water may be used directly from the ram or stored in an elevated
tank as a reserve supply; or accumulated in a pressure tank, where
additional pressure is required.

The hydraulic ram has been used since 1796, when it was invented by
Joseph de Montgolfier. The principle of its operation is that of the
utilization of the energy of flowing water. The running water is made
to give up a portion of its momentum to elevate a part of the water,
and transport it to a considerable distance. If the source of supply
and the fall is sufficient, almost any amount may be elevated and
carried to a great distance. Large rams are sometimes used as a means
of water supply for small towns. In the use of the double-acting ram,
one source of water may be used to operate the ram and water from an
entirely different source may be delivered. It sometimes happens that a
muddy stream and a clear spring are so located, that the water of the
stream can be utilized to furnish the energy for conveying the spring
water to a point where it is desired for use. This is accomplished by
the double-acting ram in a most efficient manner.

=Single-acting Hydraulic Ram.=--Fig. 140 represents the installation of
a single-acting hydraulic ram, placed to take water from a spring _E_,
and deliver it to an elevated tank at the house on the hill.

[Illustration: FIG. 140.--Hydraulic ram driven by the water from a

In case the ram must be located at a considerable distance from the
spring in order to attain the required fall, a standpipe _D_--slightly
larger than the supply pipe--is used to take advantage of the full
force of the water. In long pipes, the friction of the flowing water
absorbs a considerable amount of the energy of flow and a standpipe,
located as indicated at _D_, in the picture, will assure the full force
of the flowing water in the ram.

The ram is commonly placed in an underground pit as protection from
freezing during cold weather, and a drain from the bottom of the pit
conducts the waste water away. The supply pipe or drive pipe _B_ and
delivery pipe _C_ are buried underground below the frost line as a
protection from freezing.

In Fig. 141 a sectional view of the ram shows all of the working parts.
The air chamber _G_ is shown partly filled with water; the impetus
valve _D_ is that part of the ram which checks the flow of the running
water and forces a part of it through the valve _E_, at the bottom of
the air chamber.

[Illustration: FIG. 141.--Cross-section of a single-acting hydraulic

When inactive the valve _D_ stands open and as the water enters from
the pipe _A_, it flows through the valve to the waste pipe but as soon
as the full force of the water bears on the valve it will suddenly
close. This sudden stop of the flowing water will lift the valve
_E_, and the energy of flow, due to its sudden stopping, will force
some of the water into the chamber _G_. As this action occurs the
upward pressure against the valve _D_ is released and it reopens but
immediately closes again as the water begins to flow. This process is
kept up, each closure of the valve sending a little water into the air
chamber. As the water gradually fills the air chamber, it is subjected
to the same action as was described in the pressure tank, the air above
the surface being compressed and the pressure developed in the space
_G_ forces the water out through the delivery pipe where it attains a
force that is a factor of the height of the original fall.

The air in the chamber _G_, is subject to the same conditions of loss
as that of the pressure tank, and to be assured of a supply to give
pressure to the water, some air must be carried into the chamber with
the water. For this purpose the valve _F_ provided. After the chamber
is partially filled, there occurs a reaction in the flow of water at
each closure of the valve, which causes a little air to be drawn in
through the valve _F_ with each impulse. This air bubbles up through
the water and enters the chamber where it assures an elastic cushion
for closing the valve _E_.

The flow of water from the supply pipe is regulated at _H_ by a nut on
the stem of the impetus valve which permits its regulation. Closing the
valve slightly causes a less supply of water to be delivered; opening
the valve wider gives a greater supply.

[Illustration: FIG. 142.--Sectional view of a double-acting hydraulic

=The Double-acting Hydraulic Ram.=--The diagram of Fig. 142 illustrates
the working principle of the double-acting hydraulic ram mentioned
above; where the water from a muddy stream is used to drive the ram and
that from a separate source, as a spring is delivered.

The construction of the double-acting ram is similar to the
single-acting ram, but a separate pipe _S_ discharges spring water
directly below the valve which acts just as though it had entered at
the drive pipe. The ram in this case is receiving water from the drive
pipe _D_, which operates the valve and furnishes power for elevating
the spring water. The spring water enters the ram through the pipe _S_,
to keep the space _T_ filled, directly under the valve. The water which
enters the air chamber is, therefore, only that from the spring.

A standpipe is arranged as shown in the figure, with a check valve to
prevent the water in the ram from being forced back into the spring
water pipe after entering the ram.


Until recent years, no thought was given to private water-supply
plants, in any except the more pretentious residences. It was formerly
supposed that the cost of machinery and installation of such plants
prohibited the use of a water system in the average home. As an item
of expense in building, a satisfactory water-supply system may be
installed at a lower cost than is paid for plumbing and bathroom

In recent years much attention has been given to the design of small
water-supply plants for isolated homes, such as are required for
suburban and rural dwellings, with the result that the necessary
apparatus to suit any conditions may be obtained of any enterprising

The degree of completeness with which the plant is to be arranged will
depend on the funds to be expended, but in the most modest dwelling
some form of water-supply plant is possible. Where opportunity is given
to make the plant complete, its appointments of construction may be
elaborated to almost any extent. A suburban or country residence may be
made as perfect in point of toilet, kitchen and laundry conveniences,
as where city water and sewer service are available. The water-supply
plant may be operated by hand or by power, and if so desired may be
made completely automatic in action.

=Gravity Water-supply Plant.=--In point of simplicity, the plant shown
in Fig. 143 represents a water system that answers every purpose of a
cottage and yet is only an elevated tank for storage of water, combined
with a house force pump. The tank in this case may be made of wood or
metal and is open at the top. The water is sent into the tank by the
pump, and gravity furnishes the force for carrying it to the fixtures
in the kitchen and bathroom.

In using a tank of the kind shown in the drawing, provision should be
made for the possibility of leakage. This is arranged for by having the
tank set in a shallow pan, so constructed that in case of accident the
water may be carried away without doing damage. This type of plant is
not usually employed in cold climates, unless some provision is made
to prevent the water in the tank from freezing. Tanks of this kind are
sometimes used in cold climates but a much more desirable plant for the
purpose is described below. In Fig. 143 the water from the cistern _W_
is raised by the pump _P_, which also forces it into the tank above
the kitchen. The gravitational force given the water, because of its
elevated position is all that is necessary to carry the water to the
fixtures in the bathroom and kitchen sink. As shown in the drawing,
it furnishes a complete water system that will perform all of the
requirements of water distribution for a small family.

[Illustration: FIG. 143.--Sectional view of a cottage containing a
simple gravity water-supply plant.]

The pipes from the range boiler are attached to the water heater, which
forms a part of the kitchen range as explained on pages 116 to 120. It
receives the supply of cold water directly from the tank through the
pipe marked _C_, and the hot water from the range boiler is supplied
through the pipe _H_. Cold water is also taken from the tank directly
to each of the cold-water taps.

The pump _P_ is a house pump, such as is shown in Fig. 130. It is a
small force pump, designed to suit the conditions of domestic use and
is made to send water into the sink or into the supply tank as desired.

=Pressure-tank System of Water Supply.=--The water-supply plant shown
in Fig. 144 is another simple construction, somewhat more elaborate
than the last, so arranged that the danger of freezing is practically
eliminated. This is a simple pressure-tank system in which a tightly
built metal water tank takes the place of the elevated tank of the
previous figure, and a tank pump is used for lifting and giving
pressure to the water. It is a more complete plant than the first and
intended to accommodate a larger dwelling. The drawing shows all of the
fixtures and connecting pipes that are required in the average home. It
shows all of the appliances for connecting the pressure tank and range
boiler with the wash trays in the basement, with all of the fixtures
in the bathroom and with the fixtures in the kitchen sink. The range
boiler is the same as those previously described and connected to the
heater in an identical manner.

The original source of supply in this case is a cistern, sunk below the
basement floor. The water is lifted from the cistern by the pump and
forced into the pressure tank through a pipe near the bottom where it
furnishes the supply for the house.

The pressure tank may be of any size to suit the requirements of the
house and may be placed in either a vertical or horizontal position.
It is sometimes galvanized, as a precaution against rust, but this is
not a necessary requirement. The pipe which conveys the water from the
pump connects with the tank near the bottom. As the water enters, the
contained air above its surface is compressed into smaller and smaller
space. The pressure that is developed by the compressed air furnishes
the force by which the water is driven out of the tank and through the
distributing pipes to the various parts of the system.

If the air in the tank when empty is compressed to one-half its
original volume, then the gage pressure will be about 15 pounds to the
square inch; if the air is compressed to one-third its original volume,
that is, when the tank is two-thirds full of water, the gage pressure
will be about 30 pounds to the square inch, which is enough to supply
water at any point of a two-story building with ample force. By pumping
more water into the tank, a pressure of 50 or 60 pounds may be obtained
without difficulty; but 40 pounds is generally sufficient for all the
demands of a house plant. This is an application of the Boyle’s law
which as stated in text books of physics is: “The temperature remaining
the same, the pressure on confined gas varies inversely as its volume.”
As the volume of such a confined body of gas is made smaller, the
pressure increases in like ratio. The desired pressures are easily
attained with a hand force pump such as is shown in the drawing.

[Illustration: FIG. 144.--The pressure-tank system of water supply as
it appears in a dwelling.]

The gage-glass _G_ on the side of the tank is intended to show the
height of the water in the tank at any time, and the pressure gage
attached to the supply pipe shows the amount of pressure sustained by
the water.

=The Pressure Tank.=--The water leaves the tank by a pipe attached near
the bottom and branches to supply each fixture, to which the water is
to be conducted. In the drawing, the pipe may be traced from the point
where it leaves the tank to the various fixtures. The cold-water pipe
terminates at the range boiler, for at that point the hot-water system
begins. The range boiler is connected by two pipes to the water heater
in the kitchen range. The water heater is a part of the fire-box of the
kitchen range and so long as the fire is kept burning, water is heated
and stored in the range boiler. Where the house is furnace-heated,
the furnace fire is sometimes utilized for heating the water by use
of a coil of pipe above the fire and which may take the place of the
range heater. Various other means are also employed for heating the
water as described under range boilers. In Fig. 145 is shown a nearer
view of a pressure tank with the pump attached. The pump is in this
case identical in its action to the one shown in Fig. 132, but differs
slightly in mechanical design. The drawing shows the gage-glass _G_,
for indicating the height of water; the pressure gage _P_, which
indicates the pressure to which the water is subjected; the attachment
of the supply pipe _S_, and the delivery pipe _D_. The water tap _T_ is
provided to draw off the water when the tank is to be emptied.

[Illustration: FIG. 145.--The pressure tank complete, with the pump and
gages as used for domestic water supply.]

In operation, the air in the pressure tank furnishes the force which
sends the water through the pipes to the various points, and forces
it through the taps at the desired rate. If for any reason the air in
the tank escapes, the propelling force is destroyed. This may occur by
reason of absorption of the air by the water, due to the pressure to
which it is subjected; or to small air leaks that may develop in the
joints, which allow the air to escape. To overcome the possibility of
these occurrences, arrangement is made whereby air may be pumped into
the tank by the same pump as that which supplies the water. In this
way, the air is introduced with the water, which bubbles up through it
to the surface. If at any time the pressure in the tank is lost, it may
be replaced by pumping air alone into the tank.

=Power Water-supply Plants.=--Where the pump is expected to furnish
water to any considerable amount beyond that for household use, it
is desirable that the plant be power-driven. If the work of watering
stock, lawn sprinkling, etc., is intended, the tank and pump must be
enlarged to suit the desired amount of water, and a gasoline engine,
windmill or electric motor will be used for power. Where local
conditions will permit, a hydraulic ram may be substituted for the pump
and the pressure tank used for additional pressure and storage.

[Illustration: FIG. 146.--Tank pump operated by a small gasoline

Fig. 146 shows a plant in which the pump is driven by a gasoline
engine. In the figure, the engine _E_ is shown connected by a belt to a
speed-reducing device or “jack,” marked _J_. The object of this machine
is to reduce the speed of rotation and charge it to the required motion
for operating the pump. The jack is connected to the pump by a rod
attached to a large gear, so as to produce the desired crank motion;
and the opposite end of the rod is attached to the pump handle. The rod
may be detached at any time and the pump worked by hand.

=Electric Power Water Supply.=--Fig. 147 shows another type of power
plant in which an electric motor operates the pump. In this style of
plant, the pulley on the electric motor _M_ is connected by a belt to
the large wheel _W_, from which the crank motion is secured for driving
the pump _P_. This machine is provided with an automatic starting and
stopping device, which automatically controls the supply of water in
the system. Whenever the pressure in the tank falls to a certain point,
the change of pressure produced on the diaphram valve _A_ starts the
motor, and the pump sends water into the tank until the pressure in the
tank again reaches the amount for which the valve is set, at which time
the valve disconnects the electric contact to the motor and the pump
stops working.

[Illustration: FIG. 147.--Pressure tank supplied by an electrically
driven pump.]

=Wind-power Water Supply.=--In Fig. 148 is shown a larger and more
complete plant than the former, in which a windmill furnishes the power
for pumping and a large underground tank is utilized for the main
supply of water. The tank marked, Well Water Pressure Tank, in this
case is so placed that the end is exposed in the well curb, where the
height of the water may be observed at any time. The pump is operated
as any other of its kind, but is provided with an automatic pressure
cylinder, which controls the operation of the mill through the rise
and fall of the water in the tank. At any time the water in the tank
falls to a certain point, the pump is thrown into gear by the pressure
cylinder, and the water is pumped into the tank until a definite height
is reached; at this point the pump is automatically thrown out of gear
and remains inactive until an additional supply of water is required.
The plant is therefore automatic in its action and requires only that
the mill be kept oiled and in running order.

As shown in the drawing, the large tank receives its supply of water
from the well and aside from providing a reserve supply furnishes power
for pumping cistern water. The water from the large tank is piped
into the house for use as required, and from the same pipe is taken a
hydrant for lawn sprinkling; in addition, this water is piped to the
barn where it is used for watering stock. A branch of the same pipe is
intended to operate a water lift, which in turn furnishes the house
with soft water from the rain-water cistern for bathing, laundry, and
kitchen purposes.

[Illustration: FIG. 148.--This diagram shows the arrangement of
domestic water-supply apparatus, in which a windmill furnishes the
pressure necessary for operating the entire plant.]

=The Water Lift.=--The water lift is a combined water engine and pump,
the motive power for which is the pressure from the well-water tank.
The soft water, pumped by the water lift, is stored in the smaller
pressure tank marked Soft Water Pressure Tank in the drawing, and
furnishes a supply for the purposes mentioned. The water lift is so
constructed that when the pressure in the soft-water tank equals the
pressure in the well-water tank, the lift will stop working and will
not start again until water has been drawn from the taps. Whenever
water is drawn from any part of the system, the pressure will be
reduced and the lift will immediately begin pumping more water and will
continue until the pressure of the two tanks are the same. The system
is entirely automatic, each part depending on the power originally
supplied by the windmill. The plant could be just as successfully
operated by substituting a gasoline engine or other source of power for
the windmill. The machinery for such a plant is not at all complicated
neither is it difficult to manage, yet it is complete in every
particular and furnishes an almost ideal arrangement for a country or
suburban home.

[Illustration: FIG. 149.--The water lift.]

In order to be assured of a supply of water over periods of atmospheric
quiet, the well-water tank must be sufficiently large to supply water
for 3 or 4 days; but in case of emergency water may be pumped by hand.

A nearer view of the water lift is shown in Fig. 149. In the figure,
the right-hand cylinder with its valve _V_ is the water engine which
furnishes the power for operating the pump, enclosed in the left-hand
cylinder. The water pressure of the main supply furnishes the energy
which drives the engine, the piston rod of which is attached to the
pump piston. The engine receives its supply of water through the pipe
marked Inlet and the waste water is discharged to the sewer by the
waste pipe on the opposite side of the cylinder. The operation of the
lift is governed by an automatic regulator which so controls the engine
that it starts pumping whenever the pressure in the system falls to a
certain point. The regulator marked Adjustable Regulator in the drawing
may be adjusted to suit the water pressure desired in the distributing


    1 Air Chamber Nut
    2 Brass Tube for Air Chamber
    3 Air Chamber
    4 Brass Cock
    5 Cap Screw
    6 Leather Washer
    7 Handle Pin
    8 Pitman
    9 Handle
    10 Brass Covered Piston Rod
    11 Fulcrum
    12 Fulcrum Pin
    13 Brass Stuffing Nut
    14 Cap
    15 Fulcrum Ring
    16 Fulcrum Ring Pin
    17 Plunger
    18 Cylinder
    19 Cap Screw
    20 Lower Valve
    21 Brass Valve Seat
    22 Base
    23 Bottom Brass Ferrule
    24 Bottom Nut

FIG. 150.--The terms by which the parts of a force pump are



The disposal of sewage, in a convenient and sanitary manner is a
problem of serious importance in the equipment of isolated dwellings
with modern household conveniences. The manner of heating, lighting
and of water supply are questions of selection among a number of
established systems, but the problem of sewage disposal must in a
great measure be determined by local conditions. Unless the natural
surroundings are such as will permit sewage to be emptied directly
into a stream of considerable volume, the problem of its safe disposal
becomes one of serious importance.

Sewage is understood to mean the fluid waste from the kitchen, toilet
and laundry and has nothing whatever to do with garbage. Sewage
disposal has to do with conducting away the house waste and disposing
of it in a sanitary manner. Sewage disposal does not necessarily have
anything to do with sewage purification; although a sewage disposal
plant may be so constructed as to discharge a purified effluent, it
usually is understood to have to do alone with its disposal in a manner
that does not offend the aesthetic sense. A simple sewage plant is
anything that will take the sewage away from the house in such a way
as to produce no unsightly accumulations that will decay and produce
offensive odors.

A sewage purification plant is one in which the raw sewage from the
house drain is first liquefied, after which the liquid is passed into
a filter where it undergoes a process of bacterial disintegration and
the organic matter reduced to the inorganic state, where no further
change is possible. The water which flows from such a filter is clear
and sparkling, and is often taken for spring water. The degree of
purification given to the sewage will depend on the style of filter and
the length of time necessary for the water to pass through it.

Sewage is composed of organic matter in a fluid or part fluid
condition, contained in a large volume of water. It is not usually
the dark, heavy, foul-smelling fluid that is imagined by many, but a
turbid liquid possessing only a few of the qualities usually ascribed
to sewage. Under favorable conditions practically all of the organic
matter will be readily dissolved and the sewage will become entirely

As a liquid, the raw sewage is in the most favorable condition for
rapid decay and if left standing in the air it soon develops properties
that render it highly objectionable.

The decay of all organic matter is a process of disintegration that
ultimately ends in the elements from which it came. In the disposal of
sewage, the aim is to permit this disintegration to take place under
conditions that will be least offensive to the aesthetic sensibilities,
and in some cases to render it free from harmful properties should
there be present the bacteria of communicable disease.

The successful disposal of sewage from cities is accomplished under a
great variety of conditions. It is much easier to arrange for sewage
purification on a large scale than in a small way. The reason for this
is that in the care of a city the sewage-disposal plant is under the
supervision of a competent person, whose business it is to see that
the conditions are kept at the highest efficiency. Private plants are
left almost entirely without care, until they fail from causes that
are usually preventable. Sewage may be successfully purified under a
great many conditions, but no type of plant has as yet proven itself
successful that does not receive intelligent attention.

The most successful of small sewage disposal plant is the septic tank
system alone or in connection with an adequate form of bacterial
filter. Cesspools are not to be countenanced by people of intelligence.
The cesspool has been so universally condemned by authorities on
sanitation, that all intelligent people look upon it as a thing filthy
beyond description. Although the septic tank is little more than an
improved cesspool, the condition under which it acts is entirely
different from that which takes place in the latter and with care
and watchfulness, it may be made to work to a degree of perfection
that is surprising. The one great cause of the failure of small
sewage-disposal plants is the lack of proper care.

The process of sewage purification as now practised in the most
successful plants is largely mechanical, but bacterial action plays a
part of great importance in the completion of the process. It consists
of two stages: the tank treatment, in which the sewage is liquefied;
and the process of filtration where the liquefied sewage--commonly
called the effluent--from the septic tank undergoes a process of
filtration and bacterial purification.

=The Septic Tank.=--The septic tank alone, as used for sewage disposal,
is often termed a sewage purifying plant, when in reality it is only
intended to change the sewage into a form in which it can be readily
carried away. The word septic means putrifying, and when applied to
sewage disposal it furnishes a convenient term but has nothing to do
with purification. The septic tank furnishes only the first stage of
the purifying process, and although its effluent may be clear and
possess little odor, it is nevertheless unpurified. The septic tank
discharges an effluent of more or less completely digested sewage,
instead, as in the cesspool, of permitting it to remain a constantly
festering mass, to be slowly absorbed by the earth.

The sewage is first collected in a tank of sufficient size to contain
the discharge from the house for 24 hours. In the process of digestion
which the sewage undergoes while in the tank, it is rendered almost
entirely liquid; at the same time it is acted upon by the bacteria that
are developed, and that tend to reduce the sewage to its elemental
form. The effluent liquid which passes out of the tank is almost
colorless and possesses relatively little odor.

The tendency of the change which takes place in the tank is to nitrify
the organic matter but under ordinary conditions the action is not
fully complete. The effluent sometimes undergoes but little change
except to be reduced to a liquid. If the effluent is now allowed to
flow into a ditch where it will stand in pools, further putrification
will take place with its resulting annoyance. In case the septic tank
is to be used alone, the effluent should be conducted to a stream for
final disposal. A septic tank must be built to accommodate a certain
number of people and of sufficient size to take care of the entering
sewage. The action which goes on in the tank will render the contents
almost entirely fluid, and under good conditions the sewage will be
completely digested. When working properly, a thick scum will form on
the surface, through which filters the gases that are liberated in the
process of disintegration. The formation of the scum is an indication
that the filter is doing its best work. Should the tank be required
to take care of more sewage than it can conveniently handle, the scum
will not form and the effluent will be turbid because of the undigested

The change that takes place in the sewage while it remains in the tank
is first that of being liquefied and then disintegrated by bacterial
action. That such a change does take place is evidenced by the residue
that is found in the tank in the process of cleaning. This is a black
granular substance, composed mostly of humus and commonly known as
sludge. The amount of accumulated sludge is relatively small, and the
operation of cleaning is not necessary more than twice a year and is
not the disagreeable task one might suppose.

=The Septic Tank With a Sand-bed Filter.=--In places where the use
of the septic tank alone is not possible, it sometimes happens that
the natural conditions are such as will permit the effluent to be
drained directly into the soil. With such a condition, the effluent
goes into a filter bed composed of gravel or other loose material,
where it undergoes still further bacterial action and if the process
is complete, the water which comes from the filter bed is clear and
odorless. Under good conditions it is clear sparkling water and
contains but a small amount of impurities.

Septic tanks are made in many forms but that illustrated in Figs. 151
and 152 is commonly used. In Fig. 151 the tank is shown in position to
receive the sewage from the house drain, where it is to undergo the
first treatment and then to be conducted to a filter bed made of porous
tile, set in loose soil. The tank is shown in detail in Fig. 152. It is
a cemented brick cistern with an opening to the surface that contains
a double cover as a protection during cold weather. A brick partition
divides the tank into spaces _G_ and _H_, that contain volumes that
are to each other as 1 to 2. The tank is of such size as will hold
a volume of sewage equal to 24 hours’ use; that is, it is expected
that any portion of sewage will remain in the tank for that length of
time. The sewage enters at _A_, in such a way as will give the least
disturbance of the liquid of the tank. An opening _C_ allows the liquid
to pass from _H_ into _G_, where any additional sewage entering _H_
will displace an equal amount in _G_, which will pass out at _B_ to
the filter bed. The partition _D_ is high enough so that the scum
that forms on the surface will not pass directly into the space _G_.
The entrance and exit pipes are made of vitrified sewer tile with the
openings below the surface.

[Illustration: FIG. 151.--Sectional view of a septic tank, connected
with a sand-bed filter; for the disposal of sewage from a residence.]

As the sewage enters the tank _A_, a considerable portion will sink to
the bottom, while some will float to the top where a thick scum will
gather. By far the greatest portion of solids will be readily dissolved
in the water and the remainder will be still further reduced to liquid
form by bacterial solution. The process of disintegration that goes
on evolves a considerable amount of carbon dioxide and ammonia which
filters through the scum. The process that now goes on in the tank is
that of liquefying the organic matter and changing it from organic to
the inorganic state.

The bacteriologist recognizes in the process of sewage disintegration
the work of two classes of bacteria, the aerobic or those bacteria
that work by reason of air and do their work only in its presence and
the anaerobic or those that work in the absence of air. In the action
of the sewage-disposal plant both kinds of bacteria are at work. If,
in the final stage where the sewage passes into the filter, air can be
carried into the earth the action will be hastened.

[Illustration: FIG. 152.--Section of the septic tank in Fig. 151
showing details of construction.]

It is evident that, since the sewage entering the tank is almost
entirely dissolved, under ideal action this system would give very
little trouble, but actually as the sewage enters the tank the
disturbance caused by the incoming water forces some of the undigested
matter into the outlet and being carried into the filter bed it will be
deposited at the first opportunity. This will cause the filter bed to
fill up with undigested sewage at the point nearest the entrance, and
in course of time it will stop the pipe because of this accumulation.

To avoid such an occurrence, tanks have been built in which an
automatic siphon discharges the effluent whenever a certain quantity
has collected. Such a tank is shown in Fig. 153. With this arrangement,
the sewage enters the first tank at _A_, and passes into the second
tank at _B_. At _S_ is shown an automatic siphon, so made that when
the effluent has collected to the height of the water line, the siphon
automatically discharges the contents of the tank. This is known as a
dosage tank because periodically a dose of the effluent is discharged
into the filter bed. The volume discharged is sufficient to fill the
greater portion of the bed, and force out the air in the loose soil. As
the water filters from the bed the air is drawn in to take its place
and gives the bacteria which work in the presence of air an opportunity
to do their work. The work done by this filter bed is first to filter
out any suspended matter carried in the effluent which will lodge on
the surface of the filter material and then to undergo the slow process
of integration, and to permit the oxidation of the dissolved sewage. If
this matter is deposited faster than it disintegrates then the filter
will fill up and finally refuse to work.

[Illustration: FIG. 153.--Sectional view of a two-chamber septic tank
with a dosage siphon.]

=The Septic Tank and Anaerobic Filter.=--In places where the use of the
simple septic tank is not possible and where the character of the soil
will not permit of a natural sand-bed filter, an anaerobic filter may
be constructed through which to pass the effluent from the septic tank.

The anaerobic filter is one in which anaerobic bacterial action is
given opportunity to reduce the organic matter in the sewage to its
elemental condition. The filter may be constructed in any form that
will permit the process of filtration to be carried out in a way
that will afford good anaerobic action. The extent to which the
purification is to be carried will determine the form and size of the

In Fig. 154 is shown such a plant, where a combined septic tank and
anaerobic filter discharges its effluent into a filter ditch in which
the purifying process is continued through a bed of gravel of any
desired length. The figure illustrates a plant that was designed for
a country residence. The septic tank and anaerobic filter are located
relatively as shown in the drawing, the filter ditch following the
course of a roadway. The water is finally discharged into a little
stream, where it mingles with the water from a spring, and flows
through a meadow.

[Illustration: FIG. 154.--Sectional view of a septic tank combined with
an anærobic filter; together with the details of construction and plan
of arrangement.]

The septic tank in Fig. 154 is quite similar in construction to the
others described except that a section of sewer tile takes the place
of the brick wall between the two parts of the tank. The opening _O_,
through which the effluent is discharged, is located a little above the
center of the tank.

The anaerobic filter is a tank, rectangular in cross-section, made
with brick walls and cemented on the inside. The effluent from the
septic tank enters the anaerobic filter in a chamber, that is separated
from the main tank by a wooden grating against which rests the filter
material. As indicated in the drawing, the bottom is filled with coarse
material; stones or broken tiles about 4 inches in diameter. Above
this is a layer of material about 2 inches in diameter and above that
another layer of 1-inch material; the top is made of gravel. This forms
the anaerobic filter, in which takes place the bacterial action away
from the presence of air. The interspaces in the filter material allows
the effluent from the septic tank to seep through and deposit the
particles of matter held in suspension. The arrangement is such as is
best suited to the anaerobic action. Here, shut away from the light and
air, the organic matter in the effluent undergoes disintegration just
as would happen in the earth.

It is evident that some of the matter that should remain in the septic
tank and be removed as sludge will be carried into the anaerobic
filter. This will, of course, form an insoluble deposit that will
accumulate and in the course of time the filter will become clogged. It
should be expected that such a filter will ultimately need renewing,
for this reason the top is made of a slab of reinforced concrete that
may be raised to allow the removal and refilling of the filter material.

The automatic siphon discharges the water from the chamber _S_,
whenever it fills. The discharged water from the siphon is conducted
into a drain tile, placed in a ditch filled with gravel or other
loose material, which serves as an additional filter and in which the
water undergoes a still further purification. This filter ditch is
constructed as indicated in longitudinal section. The water from the
siphon enters the tile _C_ and seeping through the filling is drained
away in the tile shown at _D_.

The tiles are not set close together, but the joints are left open and
covered by pieces of broken tile as shown in _H_. This is to prevent
the filter material from entering the tile and thus stopping the ready
flow of the water.

The filter ditch of the plant will be constructed according to the
contour of the ground and will follow the natural drainage. The course
of the ditch--if it is desired to use one--will accommodate itself to
the character of the ground. The final discharge of the water will be
determined by the natural drainage.

That a plant of this kind will work perfectly when new is is beyond
a doubt but that it will continue indefinitely to give perfect
satisfaction is not reasonable to expect. The septic tank will require
cleaning, probably once a year. The anaerobic filter will require
renewing at intervals, depending on the amount of sewage the filter is
required to take care of and the rate at which the plant is worked,
probably once in 4 or 5 years. If the septic tank is of insufficient
size to readily digest the sewage, the accumulation of sludge in the
anaerobic filter will be greater than should occur.

It would be only reasonable to suppose that the siphon will sometimes
refuse to discharge. Even though it is an automatic siphon,
circumstances may cause it at times to fail to act. For this reason the
manhole is placed so that the siphon may be inspected and repaired,
should it be necessary. It must not be supposed that once such a
plant is in place that all of the work is over. The success of a good
sewage-disposal plant of this kind demands eternal vigilance.

[Illustration: FIG. 155.--Septic tank with a settling basin and
windmill pump.]

In the level areas where the possibilities of natural drainage is
not good, it sometimes occurs that plants such as those described
are not permissible. To overcome such conditions the plant in Fig.
155 represents an installation where the effluent is carried several
hundred feet through a drain tile before it is finally discharged into
an outlet. This plant is made up of two separate tanks, the first
acting as a septic tank, while the second tank is a settling chamber.
The water from the second chamber is pumped by windmill power and
discharged into a drain tile at the required height through which it is
carried to the place of final deposit.

=Limit of Efficiency.=--Much that has been written on the subject
conveys the impression that the septic tank alone, used under various
conditions, will eliminate disease germs and all offending features
of sewage and render it a pure water with a small amount of residue
remaining in the tank. That such is not the case is all too evident to
many who have constructed plants expecting perfect results and have
attained only partial success.

It is not reasonable that a plant giving satisfaction under the usual
conditions could accomplish its purpose under stress of work. It is
quite evident that the amount of sewage from any source cannot be
constant. It is equally evident that the effluent from the plant cannot
always be the same; but with reasonable limits of variation, a suitably
designed tank ought to take care of the sewage from a house at all
times and discharge an effluent that is reasonably clear and without
offending odor.

It should be kept in mind that, as commonly used, the chief office of
the septic tank is to do away with the things that offend the senses,
and not to make an effluent that might serve as drinking water. It must
also be kept in mind that if the disease germs enter the plant because
of sickness in the house that there is every possibility that the germs
will be in the discharged water.

The plant must be located as is directed by the natural surroundings
but the drainage must be away from buildings and particularly from

Small sewage plants are reasonably efficient and add immensely to the
comfort and healthful conditions of the home. They are not perfect in
their action but there is excellent reason to believe that the plant of
ideal construction will yet be attained.

In a flat country where drainage is difficult, the form of plant must
be modified to suit the prevailing conditions but some form of working
plant can always be devised. Small plants do not give so efficient
results as those of large size but they do very acceptable work. To do
good service they must receive attention but the actual amount of labor
they demand is small. Small sewage-disposal plants are not expensive
nor difficult to construct, and for the amount of labor and money
expended they give returns that cannot be estimated.

In determining the character of plant to be constructed, in any
particular place, local conditions will in a great measure decide the
type to be used. The degree of purity to which it will be necessary
to reduce the effluent will depend on the location of the plant and
the means of final disposal. If the effluent can be run into a stream
of sufficient volume, the septic tank alone will probably answer the

The septic tank reduces sewage to a liquid form which has some odor.
It may be carried away in an open ditch which has good flow, but if
allowed to collect in pools it will undergo further putrescence and be

It may be possible to use a small creek for final disposal but one in
which the effluent from a septic tank alone would be objectionable.
In such a case the use of the septic tank combined with an anaerobic
filter would probably give a permissible degree of purity.

With a plant composed of a septic tank and anaerobic filter, sewage
is rendered almost free from odor and the effluent will not undergo
further putrescence when collected in pools.

In many cases it is desired to purify the effluent still further,
either because of lack of means for final disposal or because the
effluent would contaminate the water into which it is discharged. In
such cases the plant will consist of the septic tank, an anaerobic
filter and a filter ditch or sand-bed filter. The effluent from such a
plant will be clear sparkling water that might be mistaken for spring

The design and construction of sewage-disposal plants has been
made a subject of investigation in a number of State engineering
experiment stations. In addition, manufacturers of cement have prepared
descriptive literature that is sent gratis on application. These
bulletins contain detailed information as to the working properties
and construction of private plants to suit the various conditions
of disposal. The following is taken by permission of the Universal
Portland Cement Co. from their bulletin on “Concrete Septic Tanks.”

[Illustration: FIG. 156.--Septic tank. This shows the construction as
if cut away along a center line following its length, also a section of
the siphon chamber and a plan of the whole construction.]

[Illustration: FIG. 156_a_.--Photographic reproduction of a concrete
septic tank, similar to that of Fig. 153. The tank requires only the
cover to make it complete.]

     “The design in Fig. 156 shows a septic tank as it would appear
     if partly cut away to expose the interior to view, and as if cut
     in half along a center line following its length. This type
     will be found to operate effectively where final disposal is
     accomplished by sub-surface irrigation. This system once started
     is self-operating due to the siphon shown in the second, or
     right-hand compartment, which at regular intervals empties the
     contents and discharges them into the line of tile from which
     the liquids leach out through joints into the soil. In a tank
     constructed as shown in the design mentioned, it is very important
     to use a siphon to empty the second compartment at intervals
     instead of allowing a continuous outward flow of contents, because
     of the tendency for drains to become clogged when liquids are
     constantly trickling through.

     “The size of tank required for residence use depends upon the
     quantity of sewage to be handled in the first chamber during a day
     of 24 hours; therefore, this compartment should be large enough
     to contain an entire day’s flow. This frequently amounts to from
     30 to 50 gallons per person per day, so the required capacity
     can readily be computed from these figures, although it must be
     remembered that the required depth for the tank should be figured
     from the top of the concrete baffle wall or partition which
     separates the first and second compartments. Another point to bear
     in mind is that the width of the first compartment should be about
     one-half its length.”



Coal is of prehistoric origin, formed from accumulation of vegetable
matter, supposed to be the remains of immense forests. In past ages the
deposits underwent destructive distillation from great heat and was
subjected to pressure, sufficient to compress it into varying degrees
of hardness. Coal is composed of carbon, hydrogen and oxygen, with
small quantities of nitrogen and varying amounts of sulphur and ash.

The coals from different geological formations vary in quality from the
hard dry anthracites to the soft wet lignites, with the intermediate
bituminous coals; all of which furnish fuels that when burned will
produce amounts of heat, depending on their composition, the quantity
of moisture contained and the conditions of their combustion.

Carbon, of which coal is principally composed, exists in different
combinations, depending on the condition of its formation. Part of the
carbon is combined with hydrogen to form hydrocarbon that may be driven
off when heated, and which forms the volatile portion of the coal. The
remainder of the carbon appears in the form of coke--when the volatile
matter is driven off--and is said to be fixed. The fixed carbon and
volatile constituents together make up the combustible.

Other ingredients of coal that require attention are the moisture, and
the incombustible matter that forms ash. Moisture varies in quantity
from as low as 0.75 per cent. in hard coal to 50 per cent. in lignite.
The amounts of ash in different coals vary from 3 to 30 per cent. of
the weights of the fuel.

The heating value of coals differs in amount by reason of the variable
quantities of fixed and combined carbons, moisture and ash. Different
coals are compared in value by the number of B.t.u. per pound of dry
coal that can possibly be developed when burned, and with these factors
are given the percentages of moisture and ash.

There are no distinct demarkations between different grades of coal.
The classifications are made because of their chief characteristics
and they commonly are graded as anthracites, semi-anthracites,
semi-bituminous and bituminous coals. These classes comprehend the
most common commercial coals of the United States. Aside from those
named are forms of coal that are occasionally found, such as graphitic
anthracite, cannel coal, etc., and the various lignites.

The value of coal as a heat-producing agent is represented by the
B.t.u. it is capable of turning to useful account. The price of coal
should be based on the amount of heat it is capable of generating
when burned. In considering the value of coal for any particular
purpose, thought must be taken as to its characteristic properties,
for coals that produce excellent results for one purpose may be very
unsatisfactory in others. Soft coal containing a large percentage of
volatile matter usually produces a great amount of smoke and unless
carefully fired this will condense and form accumulations of soot that
are objectionable. For reasons of this kind bituminous coals are often
sold at a lower price than their rated heating value might indicate.

=Anthracite or hard coal= possesses bright lustrous surfaces when newly
fractured, that when handled do not soil the hands. It contains a high
percentage of carbon, a small amount of volatile matter and little
moisture. It is greatly in demand as a domestic fuel because it burns
slowly with an intense heat, practically without flame and produces
no smoke. It invariably commands a higher price than soft coal, but
in heating value is not superior to the better grades of soft coal.
In furnaces for house heating the use of soft coal often gives better
satisfaction than hard coal.

The grades of hard coal found in the market will vary with the demand
in any locality but those recognized by the trade are:

    Egg              Coal will pass through 2¾-inch mesh screen.
    Stove            Coal will pass through  2-inch mesh screen.
    Chestnut         Coal will pass through 1⅜-inch mesh screen.
    Pea              Coal will pass through  ¾-inch mesh screen.
    No. 1 Buckwheat  Coal will pass through  ½-inch mesh screen.
    No. 2 Buckwheat  Coal will pass through  ¼-inch mesh screen.
    No. 3 Buckwheat  Coal will pass through  ⅛-inch mesh screen.

Hard coal of stove and chestnut sizes are those most commonly used
for domestic heating, because they are well suited for furnaces and
heating stoves. Of the two sizes chestnut coal is most largely used
and on account of the greater demand, the price for this size is
usually somewhat in advance of the others; at the same time the smaller
sizes--pea and buckwheat coals--are less in price for the same grade of
coal. Under conditions that will permit their use the latter coals are
an economical form of fuel.

=Bituminous or soft coal= represents the chief fuel of commerce. The
market prices of these coals are determined largely by reason of
their reputation as desirable fuel. The variations in price depend
on the physical qualities, rather than on the amount of heat evolved
in combustion. The compositions of coals vary markedly in different
localities and often in the same locality several grades are produced.
It sometimes happens that from different parts of a mine the coal will
differ very much in heat value.

Bituminous coals are roughly classified as coking and free-burning. The
former is valuable for gas manufacture and for production of coke. The
coking coals fuse on being heated, allowing the volatile portion to
escape; and when the gas has been all distilled, the residue is coke.
When used for gas making, the volatile portion forms the illuminating
gas. When burned in a furnace, the gases from soft coal burn with a
yellow flame and usually with considerable smoke. The classification
of bituminous coals differ somewhat in the East from that of the West.
Eastern bituminous coals are commonly graded:

     A. Run-of-mine coal = unscreened coal as taken from the mine.

     B. Lump coal = that which passes over a bar screen with 1-1/4-inch

     C. Nut coal = that which passes through a bar screen with
     1-1/4-inch openings and over one with 3/4-inch openings.

     D. Slack = all that which passes through a 3/4-inch bar screen.

     Western bituminous coal:

     E. Run-of-mine coal = the unscreened coal as taken from the mine.

     F. Lump coal--divides as 6-inch, 3-inch and 1-1/4-inch according
     to the diameter of the mesh through which the pieces pass the

     G. Nut coal--varying from 1-1/4-inch size to 3/4-inch in diameter.

     H. Screening = all coal which passes a 1-1/4-inch screen including
     the dust.

Heat derived from coal--or any other fuel--in the process of combustion
is due to oxidation. Combustion or burning is caused by rapid
oxidation. When oxygen combines with carbon in sufficient quantities,
carbon dioxide is formed and at the same time heat is liberated. In
burning fuel, if the carbon is completely oxidized and changed into
carbon dioxide, the greatest amount of heat is produced. The required
oxygen is furnished by the air, which through the dampers of the
furnace regulates the rate of combustion.

=Oxidation of Hydrocarbons.=--In the oxidation of hydrocarbons, as
that of burning coal gas, the combination of the elements forms carbon
dioxide and water. The presence of the water, formed in combustion,
is often shown in the formation of moisture on the bottom of a cold
vessel when placed over a gas flame. The same effect is observed in a
newly lighted kerosene lamp, when the film of moisture forms inside the
cold lamp chimney. As soon as the surfaces become heated the moisture
is evaporated. Occasionally, the accumulation of moisture in chimneys,
from this cause, is sufficient during extremely cold weather to form
ice in the part of the chimney exposed to the outside air. Chimneys
have been known to become so stopped by accumulation of ice from this
cause as to materially interfere with the draft.

The fixed carbon of the coal, when oxidized, has a constant heating
value of 14,000 B.t.u. per pound. The volatile hydrocarbons develop
amounts of heat when burned, depending on their composition, and differ
in coals from different localities. The heat obtained from the volatile
part of coal depends on its chemical composition and differs very
materially; it may be as high as 21,000 B.t.u. per pound, or as low as
12,000 B.t.u. per pound.

A high percentage of volatile matter usually indicates a fuel that
will produce a large volume of smoke, which--unless the combustion is
complete in the furnace--will deposit soot as soon as it is condensed,
either in the chimney or in the outside air. The ash has no heating
value, and the contained moisture has a negative heating effect,
because considerable heat is required to evaporate and raise it to the
temperature of the gases of the furnace. In burning fuel the moisture
uses up the heat of combustion in proportion as it appears in the coal.
The moisture is bought as coal but requires heat to get rid of it; so
the percentage of water in coal should be considered very carefully.

It is customary in comparing the heating values of coals, to state
the proportionate parts of fixed carbon, volatile matter, moisture
and ash as well as the B.t.u. per pound of dry coal. The heat value
in B.t.u. per pound of fuel is usually obtained by burning samples in
a calorimeter from which the heat per pound is calculated. The heat
value of fuels used in power plants are often determined by careful
tests of the amount of power derived for each pound of fuel burned in
the furnace. This is done by weighing the fuel burned and measuring
the water evaporated. The ashes are weighed and this weight together
with the weight of moisture present is subtracted from that of the coal
to determine the amount of combustible of the fuel. The final results
are expressed by the number of pounds of water evaporated per pound of
combustible and also the weight to water evaporated per pound of coal

=Semi-bituminous coal= represents a class between the hard and soft
grades. It contains less carbon and more volatile matter than hard
coal. It burns with a short flame with very little smoke and is
valuable as a furnace fuel. The Pocahontas coal of West Virginia is an
example of this class. Semi-bituminous coal is often called smokeless
coal, because in burning it produces relatively little smoke. It will
be noted in the table of heat values on page 192 that coal of this
variety has high heat-producing properties. It is a very friable coal
and for that reason is apt to contain considerable dust. As a furnace
fuel it produces--when carefully fired--very satisfactory results.

=Graphitic Anthracite.=--This is a type of coal found in Rhode Island
and Massachusetts which resembles both graphite and anthracite coal. It
is gray in color, very hard and burns with extreme difficulty.

=Cannel Coal.=--This is a variety of bituminous coal, rich in
hydrocarbons. It burns with a bright flame without fusing and is often
used for open fires.

=Lignite.=--This is a type of fuel that in point of geological
formation represents the condition between true coal and peat. Lignite
occurs in immense deposits throughout the middle portion of the
western half of the United States, where beds 20 feet in depth are not
uncommon. It varies in color from black to brown and in many localities
is known as brown coal.

When newly mined, lignite contains a large percentage of water,
sometimes as high as 50 per cent. On account of this large moisture
content it has a relatively low calorific value, but when dry the
amount of heat evolved per pound compares very favorably with soft coal.

=Peat.=--As a fuel, peat has been used very little in the United States
on account of the abundance of the better grades of fuel, but in many
parts of the country it is used locally to a considerable extent. In
peat bogs from which the fuel is taken, the peat is formed from grasses
and sedges which in time produce a carbonaceous mass that becomes
sufficiently dense to be taken out in sections, with a long narrow
spade. The peat is then built into piles where after drying it is ready
to be burned.

=Wood.=--On account of its relative scarcity and correspondingly high
price, wood is no longer a commercial fuel of any consequence. The low
heating value of wood as compared with coal makes it a prohibitive fuel
except in forest localities. Wood is commonly sold by the cord and no
attention is given by dealers to its value in heat-producing capacity.

The desirability of wood as a fuel is chiefly that of reputation. It
is usually considered that hickory is the ideal fire wood, dry maple a
close second and that oak is next in desirability as fuel; following
which are ash, elm, beech, etc., depending on the density of the wood.
The price of wood per cord depends on the nearness and abundance of

The actual heating values of different woods as determined by Gottlieb
show that per pound of dry wood there is little difference in heat
value between different kinds of hard woods, and that pine gives per
pound the highest value of all. The table given below was taken from
“Steam” published by the Babcock-Wilcox Co.

                     Per cent. of    B.t.u. per
    Kinds of wood        ash           pound

        Oak             0.37           8,316
        Ash             0.57           8,480
        Elm             0.50           8,510
        Beech           0.57           8,591
        Birch           0.29           8,586
        Fir             0.28           9,063
        Pine            0.37           9,153
        Poplar          1.86           7,834
        Willow          3.37           7,926

In considering this table it must be kept in mind that the values are
for dry wood per pound.

As given in Kent’s “Engineer’s Pocket Book” the weights of different
fuel woods per cord (thoroughly air-dried) are about as follows:

  1 cord hickory or
    hard maple          4,500 pounds equal to 1,800 pounds coal
  1 cord white oak      3,850 pounds equal to 1,540 pounds coal
  1 cord beech, red
    and black oak       3,250 pounds equal to 1,300 pounds coal
  1 cord poplar,
    chestnut and elm    2,350 pounds equal to   940 pounds coal
  1 cord average pine   2,000 pounds equal to   800 pounds coal

The above values in pounds of coal may be taken to represent average
bituminous coals. As given by Suplee’s “Mechanical Engineers’ Reference
Book,” eight samples of coals representing bituminous coals from mines
east of the Mississippi River give an average heating value of 13,755
B.t.u. per pound.

=Charcoal.=--This is made from wood by driving off the volatile
constituents; the residual carbon, which forms the charcoal is a fuel
that burns without smoke or flame. Charcoal is made by piling wood in
a heap, which is covered with earth. In the bottom of the heap a fire
generates the necessary heat for distilling off the volatile matter.
Charcoal holds to wood the same relation that coke bears to coal.

=Coke.=--This is the residue from the distillation of coal. It
comprises from 60 to 70 per cent. of the original coal and contains
most of the carbon and all of the ash of the coal. Coke is gray in
color and has a slightly metallic luster; it is porous, brittle and in
handling gives out something of a metallic ring. It is often sold for
fuel as a byproduct by gas factories. In heating value gas-coke gives
about 14,000 B.t.u. per pound when dry and as a consequence is rated
as an excellent fuel. Clean coke burns without flame and is capable of
producing an intense heat. On account of its porous nature it occupies
a relatively large volume per ton. It is most successfully burned in
stoves and furnaces with large fire-boxes.

=Gas-coke=, which is the residue from the gas retorts, is somewhat
inferior in heating value to coke made in ovens but it is an excellent
fuel where furnaces are adapted to its use. Gas-coke is often stored,
by piling it in heaps, in the open and on account of its porous nature
it absorbs considerable moisture. Where exposed to the weather the
amount of contained moisture depends on the amount of rain or snow the
coke has absorbed. This amount is easily determined by weighing a fair
sample and driving off the moisture in an oven. The sample should be
weighed several times until the weight remains constant.

=Briquettes.=--Briquetted coal and other fuels are produced by
compressing coal dust or other powdered fuel, mixed with coal tars or
other bituminous binder in sufficient quantity to cause the adhesion of
the particles when pressed into form under great pressure. Owing to the
relative cheapness of fuel, briquettes have been used but very little
in the United States. With the advance in the price of coal of the past
few years, they have found a place on the market and have become a
common form of fuel.

The heat value of briquettes will depend on the kind and quality of
material that enters into their composition. Quite generally, they
produce heat equal to the average grade of soft coal. In the Northwest
briquettes made of West Virginia semi-bituminous coal sell at the same
price as run-of-mine coal of the same quality. Their use has proven
satisfactory as a furnace fuel and they will very likely be sold in
increasing quantities.

=Comparative Value of Coal to Other Fuels.=--Until a comparatively
recent time, coal has been sold by weight and reputation alone; but
conditions are rapidly approaching, which will require it to be sold
according to its composition and heating value. Among manufacturers and
others using large quantities of fuel, the practice of contracting for
coal by specification is becoming increasingly common. The determining
factors are the amounts of moisture, ash, sulphur, carbon, and volatile
matter the coal contains, as well as the size of the pieces and freedom
from dust. In a few of the most progressive cities, coal dealers are
required to supply coal for schools and other municipal uses, which
has been subject to the approval of the City Engineer. The time is
not far distant when dealers will be required to submit samples of
all fuel, for sale to the public, to the examination of the municipal

The following table of the heating values of various fuels is taken
from Benson’s “Industrial Chemistry.”


    Acetylene, from carbide at 10 cents per pound            600
    Denatured alcohol, at 40 cents per gallon              2,000
    Air gas (from gasoline, 80°Bé at 25 cents per gallon)  3,000
    Water gas, at $1 per 1000 cubic feet                   3,000
    Coal gas, at $1 per 1000 cubic feet                    6,500
    Gasoline, at 20 cents per gallon                       7,500
    Kerosene, at 15 cents per gallon                      11,000
    Natural gas, at 50 cents per 1000 cubic feet          18,000
    Charcoal, at 10 cents per bushel (15 pounds)          20,000
    Petroleum at 5 cents per gallon                       30,000
    Producer gas, from anthracite, $7 per ton             30,000
    Producer gas, from coke, $5 per ton                   36,000
    Anthracite, at $7 per ton                             46,000
    Producer gas, from soft coal, at $3 per ton           50,000
    Coke, at $5 per ton                                   54,000
    Mond producer gas from soft coal, at $3 per ton       65,000
    Soft coal, at $3 per ton                              80,000

=Price of Coal.=--The value of coal as a fuel will depend on the
amount of heat it is capable of producing when burned; its price
should therefore be determined by the heating value per pound of fuel
as purchased. Secondary determining factors in price are those of
convenience of handling and the difficulty in burning the fuel such
as the size and uniformity of the pieces, the formation of clinkers,
smoke and accumulation of soot. Soft coals, containing a large amount
of volatile matter, usually produce much soot and smoke and as a
consequence sell for a lower price than coals that produce little smoke.

The selection of fuels will depend on the type of heating plant in
use, whether by stoves or by furnaces. If by stoves, whether it is
possible to use soft coal as a fuel. The automatically fed stove, of
the base-burner type, are usually designed for the use of hard coal and
in such stoves the use of soft coal would not be possible. Other stoves
and furnaces are usually capable of burning soft coal with varying
degrees of satisfaction, depending on the design and surrounding

The following prices, from the local market, show the usual ratings of
various fuels in common use. These prices vary with the locality and
somewhat with the season. It is usually possible to purchase coal at
some reduction in price during the summer months when the demand for
coal is light.

    Hard coal--stove size                             $10.25 per ton
    Hard coal--nut size                                10.50 per ton
    Semi-bituminous--run-of-the-mine                    9.00 per ton
    Pennsylvania bituminous--run-of-the-mine            7.50 per ton
    Soft coal--Ohio--run-of-the-mine                    7.50 per ton
    Soft coal--Illinois--bituminous--run-of-the-mine    7.50 per ton
    Soft coal--Iowa--bituminous--run-of-the-mine        7.50 per ton
    Briquettes-mixture semi-bituminous coal dust        9.00 per ton
    Wood (oak), sawed, stove length and split           8.50 per cord

The price of coal is determined in many localities by the distance from
the sources of supply and the means of transportation. The fact that
coals from all of the principal mining areas from Pennsylvania, west to
Iowa, are sold at points in the Northwest for the same price, is due in
greatest measure to transportation rates on the Great Lakes. The prices
of Eastern coals at Duluth are such that in competition with Western
coals they are sold at the same price as is shown by the table.

It is usually impossible for the average householder, or even the
dealer, to determine definitely the exact locality from which his
fuel is mined. Even when such information is obtainable, the quality
is still in doubt, unless analysis is obtainable by sample. The data
given in the following tables is such as will furnish a fair knowledge
of the relative heating values of coals from the principal mining
areas of the United States. The data was obtained from a considerable
number of authorities but chiefly from the reports of the United States
Geological Survey. The different items are not intended to be exact,
they merely represent reliable average conditions.

The varying conditions of available heat and percentage of moisture
given in the following table are such as to be of little use to those
unaccustomed to problems of this kind, unless a systematic method of
comparison is made of the different fuels.


          |          |   3    |        |        |      |    7    |
          |    2     |Number, |        |   5    |  6   | B.t.u.  |
     1    | Kind of  |  of    |Moisture|Volatile|Fixed |pound per|  8
  Locality|  coal    |samples |        | matter |carbon| dry coal| Ash
          |          |examined|        |        |      |         |
  Pa.     |Anthracite|   12   |   5.05 |   5.52 | 82.54|  12,682 |11.53
  Md.     |Semi-     |    5   |   2.39 |  17.73 | 75.44|  14,530 | 7.40
          |bituminous|        |        |        |      |         |
  Pa.     |Semi-     |   15   |   3.60 |  19.26 | 74.46|  14,211 | 8.32
          |bituminous|        |        |        |      |         |
  W. Va.  |Semi-     |   12   |   2.50 |  19.00 | 75.70|  14,758 | 5.24
          |bituminous|        |        |        |      |         |
  Ala.    |Bituminous|    6   |   3.55 |  29.99 | 59.24|  13,522 |10.73
  Ark.    |Bituminous|    2   |   1.42 |  16.58 | 73.37|  14,205 |10.05
  Colo.   |Bituminous|    6   |   9.89 |  37.34 | 52.53|  12,325 |10.32
  Ill.    |Bituminous|   22   |  10.31 |  36.73 | 50.52|  11,504 |12.73
  Ia.     |Bituminous|    8   |   7.72 |  39.15 | 50.54|  12,656 |10.33
  Kan.    |Bituminous|    3   |   4.25 |  32.20 | 51.17|  12,031 |13.75
  Ky.     |Bituminous|    9   |   5.99 |  34.58 | 56.56|  13,341 | 8.86
  Mo.     |Bituminous|    9   |  11.52 |  37.85 | 48.11|  12,398 |14.04
  Ohio.   |Bituminous|   14   |   5.65 |  38.51 | 50.59|  12,839 |10.65
  Okla.   |Bituminous|    3   |   5.72 |  34.83 | 52.76|  12,648 |12.41
  N.M.    |Bituminous|    1   |  12.17 |  36.31 | 51.17|  12,126 |12.52
  Pa.     |Bituminous|   15   |   2.44 |  33.41 | 58.31|  13,732 | 8.40
  Tenn.   |Bituminous|    4   |   2.53 |  36.58 | 58.21|  14,098 | 5.47
  Tex.    |Bituminous|    3   |   3.84 |  35.05 | 48.99|  12,302 |15.96
  Va.     |Bituminous|    5   |   2.71 |  31.32 | 62.47|  14,025 | 6.92
  W. Va.  |Bituminous|   10   |   2.61 |  33.92 | 58.80|  14,094 | 7.27
  Colo.   |Lignite   |    6   |  19.75 |  45.21 | 45.85|  10,799 | 8.93
  N. D.   |Lignite   |    5   |  35.93 |  44.33 | 43.21|  10,420 |12.45
  Tex.    |Lignite   |    6   |  30.86 |  44.06 | 39.21|  10,297 |16.76
  Wyo.    |Lignite   |    4   |  14.71 |  48.47 | 44.49|  11,608 | 7.035

The following table was prepared from the date of that preceding
combined with the prices of various coals to be obtained in the local
market. The table is intended to present a method of comparing the
values of fuels from different coal areas. The consumer is interested
to know the amount of heat purchased in the form of fuel. The table
shows in the column headed “Heat per $1,” the number of B.t.u.
purchased for $1 in coal; the number of available B.t.u. in the
different kinds of coal may be taken as a relative comparison of their
values as fuel.

The gas-coke in the table is that sold by the local gas company. The
amount of moisture in this case is relatively high because of the fact
that the coke is stored in a yard exposed to the weather, where it
absorbs all precipitated moisture. A less amount of moisture would give
a higher value for the same fuel.

              |     |      |          |         |B.t.u. per |
              |Price| Per  |          |B.t.u. to|100 ÷ cost |
              | per |cent.,|B.t.u. per|evaporate| per 100   |   Heat
  Kind of coal| ton |water |100 pounds|  water  |  pounds   |   per $1
  Bituminous   $7.50  2.44  1,340,000 -  3,439  = --------- = 3,564,000
  Pennsylvania                                      $0.375       B.t.u.
  Semi-                                           1,415,685
  bituminous   $9.00  3.06  1,420,000 -  4,315  = --------- = 3,145,000
  West Virginia                                     $0.45        B.t.u.
  Gas-coke     $7.00 10.00  1,117,900 - 16,888  = --------- = 3,145,000
                                                    $0.35        B.t.u.
  North                                            607,282
  Dakota       $4.50 35.90    668,000 - 50,728  =  -------  = 2,703,000
  lignite                                           $0.225       B.t.u.
  Bituminous   $7.50 10.31  1,032,000 - 14,398  = --------- = 2,980,000
  Illinois                                          $0.375       B.t.u.
  Bituminous   $7.50 13.10  1,012,000 - 18,471  =  -------  = 2,652,000
  Iowa                                              $0.375       B.t.u.
  Hard coal   $10.50  3.05  1,230,000 -  4,195  = --------- = 2,335,000
  Pennsylvania                                      $0.525       B.t.u.

Semi-bituminous coal commands considerable favor as a house-heating
fuel, because of the fact that it burns with much less smoke than
bituminous coal. In available heat it is considerably above the Western
bituminous coal and it sells at a price $1.50 higher per ton. The
reason for the difference in price is not so much on account of its
heating value, as because of relatively small amount of smoke produced
in combustion. Other coals capable of producing more heat are sold at
less price because of smoke and soot produced in burning.

Hard coal at $10.50 is the most expensive coal of all. The ratio of
available heat units per $1 for hard coal, as compared with the best
soft coal, is as 23 is to 35. This means that at the stated prices
those who burn hard coal pay the additional price, because of the
physical properties it possesses.

In constructing the above table, 100 pounds of coal was taken as a unit
of comparison. The price per ton is that given in the table of local
prices. The per cent. of moisture and the B.t.u. per pound of fuel was
taken from table on page 192.

In explaining the method by which the different items were obtained, it
will be necessary to discuss briefly the condition of combustion and
the heat losses that take place when fuel is burned.

The moisture in the fuel is the undesirable part, because it requires
a large amount of heat to dispose of it. It is looked upon as so much
water, that must be raised in temperature from that in which it is
taken from the coal bin to the temperature and condition of vapor in
which it passes into the chimney. When the fuel enters the furnace
the water is heated to the boiling point. In changing temperature
it absorbs 1 B.t.u. for each pound of water, through each degree of
change. Suppose that, as in the case of Pennsylvania bituminous coal
which contains 2.44 pounds of water to each 100 pounds of coal, the
coal entering the furnace was at 50°F. To raise its temperature to the
boiling point (212°F.) required a change of 162°. The 2.44 pounds of
water raised this amount

            162 × 2.44 = 395.28 B.t.u.

To change the 2.44 pounds of water, into steam at the atmospheric
pressure requires 969.7 B.t.u. (heat of vaporization), practically 970
B.t.u. per pound of water. The heat required to vaporize 2.44 pounds of
water is

            2.44 × 970 = 2366.80 B.t.u.

The vapor is now raised in temperature, to that of the furnace, which
we may assume is 1200°F. The furnace being at atmospheric pressure the
vapor merely expands in volume as a gas. The specific heat of steam at
atmospheric pressure is 0.464; that is, 1 pound of steam requires only
0.464 B.t.u. to raise it a degree, and 2.44 pounds of water will absorb

            0.464 × 2.44 × 1200 = 1356.00 B.t.u.

Of this last amount of heat, approximately 50 per cent. is recovered as
the gases pass through the furnace. The total loss of heat due to the
evaporation of the water is

    Raising temperature from normal to 212°             395 B.t.u.
    Evaporation                                       2,366 B.t.u.
    Changing temperature of vapor, less 50 per cent.    678 B.t.u.
    Total heat loss                                   3,439 B.t.u.

In the 100 pounds of coal under consideration, there is 100 pounds,
less 2.44 pounds of water, or 97.56 of dry coal, each pound of which
contains 13,732 B.t.u. as given by the table on page 193. This gives

    97.56 × 12,682 = 1,339,753 = practically 1,340,000 B.t.u.

From this quantity is subtracted the loss of heat, 3439.

    1,340,000 - 3439 = 1,336,561 B.t.u.

This represents the total available heat in 100 pounds of coal. If this
quantity is now divided by the cost of 100 pounds of coal at $7.25 per
ton, the result, 3,564,000 B.t.u., will be the available heat bought
for $1 as given in column 7 of the table.



The physical effect of atmospheric humidity has come to be recognized
by all who deal in problems of house heating, sanitation and hygiene.
The difference in effect of dry atmosphere, from that of air containing
a desirable degree of moisture, is very noticeable in all buildings
that are artificially heated. The effect of dry air is made apparent
in the average home during the winter months by the shrinking of
the woodwork and furniture. The absorption of the moisture from the
building which is usually termed “drying out,” causes the joints in the
floors and casements to open, doors to shrink until they fail to latch
and drawers that have opened with difficulty during the summer then
work freely.

Winter time is the season of prevalent colds, chaps and roughness of
the skin, not so much on account of cold weather as because of dry air.
The skin which is normally moist is kept dry by constant evaporation
with the attending discomfort of an irritated surface and the results
which follow.

The humidity of the air in which we live and on which we depend for
life has much to do with the bodily comfort we derive in existence, and
is suspected of being the cause of many physical ailments. Ventilation
engineers not only recognize this condition but have found means of
controlling it. It is possible to so control atmosphere temperature and
humidity of buildings as to produce any desired condition.

=Humidity of the Air.=--The amount of water vapor in the air is called
the humidity of the air. It may vary from a fraction of a grain per
cubic foot in extremely cold weather, to 20 grains per cubic foot
during the occasional hot weather of summer.

Since the amounts of moisture that air will hold depends on its
temperature, and as the air is ordinarily only partly saturated, the
varying amount of moisture are expressed either as _relative humidity_
and stated in per cent. saturation or in the actual weight of water in
grains per cubic foot and known as _absolute humidity_.

The relative humidity of the atmosphere is the amount of moisture
contained in a given space as compared with the amount the same air
could possibly hold at that temperature. Warm air will hold more
moisture than the same air when cold. Air absorbs water like a sponge
to a point of saturation. When the air is filled with moisture, any
change which takes place to reduce the temperature also reduces its
capacity to hold the water vapor and the excess is deposited as dew.
This supersaturation ordinarily takes place near things which lose
their heat faster than the surrounding air and the nearest colder
surface acts as a condenser to receive the drops of dew. Grass being in
convenient position is the commonest receptacle for dew formation. If
the dew forms in the air it falls as rain, but if the temperature of
the dew-point is below freezing, the dew immediately freezes and snow
is the result.

In the consideration of problems that involve atmospheric moisture,
both relative and absolute humidity are factors of common use, that are
capable of exact determination. The relative humidity of the air is
most readily determined and as it expresses the state of the atmosphere
in which plants and animals live and thrive, as opposed to other
conditions of humidity in which they sometimes sicken and die, it is
one of the indicators of the quality of atmospheric air.

In the subject of ventilation, which is undertaken later, it will be
found that a definite knowledge of atmospheric humidity has much to do
with the successful operation of ventilation apparatus. Most people
recognize the “balmy air of June” without realizing just why at the
same temperature other seasons are not so delightful. In reality it
is the condition of atmospheric humidity combined with an agreeable
temperature that gives the kind of air in which we find the greatest
degree of comfort.

The effect of moderately warm humid air is that of higher temperature
than the thermometer indicates. When the atmosphere is near the point
of saturation, the evaporation which usually goes on, from the surface
of the body, practically ceases. In summer time a temperature of 85°F.
with relative humidity of 90 per cent. saturation seems warmer than a
temperature of 100° at 40 per cent. saturation, because of the cooling
effect produced by the increased evaporation due to the drier air.

In winter, when most of the time is spent indoors, in an atmosphere
that is very dry, the sensation of discomfort produced by the lack of
humidity oftentimes leads to physical derangements that would never
appear under more desirable conditions. The cause of many ailments of
the nose, throat and lungs during the winter months is attributed by
physiologists to breathing almost constantly the dry vitiated indoor
air. The cause of dry air in buildings is not difficult to explain; it
is a great deal more difficult to realize that the lack of water breeds
so much discomfort.

In order to express the condition of humidity that may exist in the
average dwelling, office or school-room during the winter, it is most
convenient to refer to the results of varying atmospheric conditions
that are given in Table 1--Properties of Air--which appears below. In
the second column of the table, under the heading “Weight of vapor per
cubic foot of saturated air,” will be found the amount of moisture
in grains per cubic foot that will be required to humidify air at
different temperatures. It will be seen that at 10° the air will
contain, when fully saturated, only 1.11 grains of water, while at 70°
temperature the same air would hold 8 grains of water. These amounts
will be found in the column opposite the temperature readings. It is
at once evident that when saturated air at 10° is raised to normal
temperature 70°, the original amount of moisture is contained in an
atmosphere capable of holding 8 grains of water. Its relative humidity
will therefore be 1.11/8, practically 14 per cent. saturated. Unless
moisture is received by the air from some other source this condition
will produce a very dry atmosphere.

The normal atmospheric temperature of 70°F. with a relative humidity
of 50 to 60 per cent. saturation produces a condition that is one of
agreeable warmth to the average person in health and is recognized as
the atmosphere most desirable. To some, this state of temperature and
humidity is that of too much warmth and a temperature of 68°, with the
same humidity, is most agreeable. At the same temperature, a reduction
of the humidity to 20 per cent. saturation will produce a feeling of
discomfort and the sensation will be that of a lack of heat. The cause
for this latter feeling is due to excessive evaporation of moisture
from the body.


               |  Weight of  |
               |  vapor per  |Weight of
    Temperature|cubic foot of|cubic foot of
    of the air |saturated air|saturated air
    Fahrenheit |   Grains    |   Grains
        10°    |    1.11     |    589.4
        11     |    1.15     |    588.1
        12     |    1.19     |    586.8
        13     |    1.24     |    585.5
        14     |    1.28     |    584.2
        15     |    1.32     |    582.9
        16     |    1.37     |    581.6
        17     |    1.41     |    580.3
        18     |    1.47     |    579.1
        19     |    1.52     |    577.8
        20     |    1.58     |    576.5
        21     |    1.63     |    575.3
        22     |    1.69     |    574.0
        23     |    1.75     |    572.7
        24     |    1.81     |    571.5
        25     |    1.87     |    570.2
        26     |    1.93     |    569.0
        27     |    2.00     |    567.7
        28     |    2.07     |    566.5
        29     |    2.14     |    565.3
        30     |    2.21     |    564.1
        31     |    2.29     |    562.8
        32     |    2.37     |    561.6
        33     |    2.45     |    566.4
        34     |    2.53     |    559.2
        35     |    2.62     |    558.0
        36     |    2.71     |    556.8
        37     |    2.80     |    555.6
        38     |    2.89     |    554.4
        39     |    2.99     |    553.2
        40     |    3.09     |    552.0
        41     |    3.19     |    550.8
        42     |    3.30     |    549.6
        43     |    3.41     |    548.4
        44     |    3.52     |    547.2
        45     |    3.64     |    546.1
        46     |    3.76     |    544.9
        47     |    3.88     |    543.7
        48     |    4.01     |    541.3
        49     |    4.14     |    542.5
        50     |    4.28     |    540.2
        51     |    4.42     |    539.0
        52     |    4.56     |    537.9
        53     |    4.71     |    536.7
        54     |    4.86     |    535.5
        55     |    5.02     |    534.4
        56     |    5.18     |    533.2
        57     |    5.34     |    532.1
        58     |    5.51     |    534.9
        59     |    5.69     |    529.8
        60     |    5.87     |    528.6
        61     |    6.06     |    527.0
        62     |    6.25     |    526.3
        63     |    5.45     |    525.2
        64     |    6.65     |    524.0
        65     |    6.87     |    522.0
        66     |    7.08     |    521.7
        67     |    7.30     |    520.0
        68     |    7.53     |    519.4
        69     |    7.76     |    518.3
        70     |    8.00     |    517.2

The evaporation of moisture is always accompanied with the loss of heat
required to produce such change of condition. This is known as the heat
of vaporization and represents a definite amount of heat that is used
up whenever water is changed into vapor. No matter what its temperature
may be--whether hot or cold--when water is vaporized, a definite
amount of heat is required to change the water into vapor.

Water may be evaporated at any temperature; even ice evaporates. A
common instance of the latter is that of wet clothes which “freeze dry”
in winter weather when hung on the clothes line. The rate at which
evaporation takes place depends on the dryness of the surrounding air
and the rapidity of its motion. In dry windy weather evaporation is
most rapid.

As before stated, whenever water evaporates--at no matter what
temperature--a definite quantity of heat is necessary to change the
water into vapor. The exact amount of heat required to produce this
change varies somewhat with the temperature and atmospheric pressure
but it always represents a large loss of heat. At the boiling point of
water (212°F.) the heat of vaporization is 970 B.t.u. for each pound of
water evaporated, but at a lower temperature it is greater than that
amount. At the temperature of the body (98.6°) the heat necessary to
evaporate a pound of moisture from its surface is 1045 B.t.u.

It is the absorption of heat due to evaporation that cools the air of a
sprinkled street. The more rapid the evaporation the more pronounced is
the decline of temperature in the immediate vicinity. The same effect
is produced when moisture is evaporated from the surface of the body.
The acceleration of evaporation caused by a breeze or the blast of air
from an electric fan is that which produces the chilling sensation to
the body. During winter weather the effect of the cold wind is rendered
more severe by evaporation of moisture from the body. In health, the
body being in a slightly moist condition, the evaporation which goes
on from its surface is what keeps it cool in warm weather, but if on
account of excessive dryness of the surrounding air the evaporation is
very rapid, a sensation of cold is the result.

Not only does excessively dry air produce the sensation of chilliness
but the loss of heat from the body due to sudden or long exposure
effects the general health and is conducive to chills that are followed
by fever. In health the temperature of the body is constant and
normally 98.6°F.; any condition that reduces that temperature tends
toward a lowering of vitality and the consequent inability to withstand
the attack of disease. In a very dry atmosphere the skin, instead
of being slightly moist, is kept dry, the result of which is the
irritation that produces chaps and roughness of the surface.

Reports of the U. S. Weather Department show that the relative humidity
of Death Valley, which is the driest and hottest known country, during
the driest period of the year--between May and September--averages 15.5
per cent. saturation. In winter, many buildings, particularly offices
and school buildings are not far from that atmospheric condition,
constantly. Under the usual conditions of house heating, there is an
almost absolute lack of means to give moisture to the air. Almost
without exception steam-heating plants and hot-water heating plants in
office buildings and dwellings are without any provision for changing
the atmospheric humidity.

In school buildings that are not kept under a more desirable condition
of temperature and humidity, the general health is impaired and the
behavior of the pupils very markedly influenced. The tension of a
school-room full of fidgety nervous children can be very promptly and
greatly reduced by the introduction of water vapor into the air to 50
per cent. saturation.

All modern school buildings, auditoriums, etc., are provided--aside
from the heating plants--with means of ventilating in which the
entering air is washed and humidified to the desired degree, before
being sent into the rooms.

The popular conception of the hot-air furnace method of heating is that
it produces particularly dry air, when in reality it is the only type
of house-heating plant in which any provision is made for adding water
to the air. These furnaces are usually furnished with a water reservoir
by use of which the humidity may be raised to a desirable point.

Much of the water which enters the air of the average home, during
winter weather, comes from the evaporation that goes on in the kitchen.
Usually on wash days the humidity is raised to a marked degree and that
day is commonly followed by a short period of agreeable atmospheric
condition. The arrangement of many houses is such that a much-improved
condition of humidity might be obtained from the kitchen by continuous
evaporation of water from a tea-kettle.


         Depression of wet-bulb thermometer (_t_-_t'_)

  Air temp. _t_ | 1.0| 2.0| 3.0| 4.0| 5.0| 6.0| 7.0| 8.0| 9.0|10.0
        35      | 91 | 82 | 73 | 64 | 55 | 46 | 37 | 29 | 20 | 12
        36      | 91 | 82 | 73 | 65 | 56 | 48 | 39 | 31 | 23 | 14
        37      | 91 | 83 | 74 | 66 | 58 | 49 | 41 | 33 | 25 | 17
        38      | 91 | 83 | 75 | 67 | 59 | 51 | 43 | 35 | 27 | 19
        39      | 92 | 84 | 76 | 68 | 60 | 52 | 44 | 37 | 29 | 21

        40      | 92 | 84 | 76 | 68 | 61 | 53 | 46 | 38 | 31 | 23
        41      | 92 | 84 | 77 | 69 | 62 | 54 | 47 | 40 | 33 | 26
        42      | 92 | 85 | 77 | 70 | 62 | 55 | 48 | 41 | 34 | 28
        43      | 92 | 85 | 78 | 70 | 63 | 56 | 49 | 43 | 36 | 29
        44      | 93 | 85 | 78 | 71 | 64 | 57 | 51 | 44 | 37 | 31

        45      | 93 | 86 | 79 | 71 | 65 | 58 | 52 | 45 | 39 | 33
        46      | 93 | 86 | 79 | 72 | 65 | 59 | 53 | 46 | 40 | 34
        47      | 93 | 86 | 79 | 73 | 66 | 60 | 54 | 47 | 41 | 35
        48      | 93 | 87 | 80 | 73 | 67 | 60 | 54 | 48 | 42 | 36
        49      | 93 | 87 | 80 | 74 | 67 | 61 | 55 | 49 | 43 | 37

        50      | 93 | 87 | 81 | 74 | 68 | 62 | 56 | 50 | 44 | 39
        51      | 94 | 87 | 81 | 75 | 69 | 63 | 57 | 51 | 45 | 40
        52      | 94 | 88 | 81 | 75 | 69 | 63 | 58 | 52 | 46 | 41
        53      | 94 | 88 | 82 | 75 | 70 | 64 | 58 | 53 | 47 | 42
        54      | 94 | 88 | 82 | 76 | 70 | 65 | 59 | 54 | 48 | 43

        55      | 94 | 88 | 82 | 76 | 71 | 65 | 60 | 55 | 49 | 44
        56      | 94 | 88 | 82 | 77 | 71 | 66 | 61 | 55 | 50 | 45
        57      | 94 | 88 | 83 | 77 | 72 | 66 | 61 | 56 | 51 | 46
        58      | 94 | 89 | 83 | 77 | 72 | 67 | 62 | 57 | 52 | 47
        59      | 94 | 89 | 83 | 78 | 73 | 68 | 63 | 58 | 53 | 48

        60      | 94 | 89 | 84 | 78 | 73 | 68 | 63 | 58 | 53 | 49
        61      | 94 | 89 | 84 | 79 | 74 | 68 | 64 | 59 | 54 | 50
        62      | 94 | 89 | 84 | 79 | 74 | 69 | 64 | 60 | 55 | 50
        63      | 95 | 90 | 84 | 79 | 74 | 70 | 65 | 60 | 56 | 51
        64      | 95 | 90 | 85 | 79 | 75 | 70 | 66 | 61 | 56 | 52
  Air temp. _t_ |11.0|12.0|13.0|14.0|15.0|16.0|17.0|18.0|19.0|20.0
        35      |  4 |    |    |    |    |    |    |    |    |
        36      |  6 |    |    |    |    |    |    |    |    |
        37      |  9 |  1 |    |    |    |    |    |    |    |
        38      | 12 |  4 |    |    |    |    |    |    |    |
        39      | 14 |  7 |    |    |    |    |    |    |    |

        40      | 16 |  9 |  2 |    |    |    |    |    |    |
        41      | 18 | 11 |  5 |    |    |    |    |    |    |
        42      | 21 | 14 |  7 |  0 |    |    |    |    |    |
        43      | 23 | 16 |  9 |  3 |    |    |    |    |    |
        44      | 24 | 18 | 12 |  5 |    |    |    |    |    |

        45      | 26 | 20 | 14 |  8 |  2 |    |    |    |    |
        46      | 28 | 22 | 16 | 10 |  4 |    |    |    |    |
        47      | 29 | 23 | 17 | 12 |  6 |  1 |    |    |    |
        48      | 31 | 25 | 19 | 14 |  8 |  3 |    |    |    |
        49      | 32 | 26 | 21 | 15 | 10 |  5 |    |    |    |

        50      | 33 | 28 | 22 | 17 | 12 |  7 |  2 |    |    |
        51      | 35 | 29 | 24 | 19 | 14 |  9 |  4 |    |    |
        52      | 36 | 30 | 25 | 20 | 15 | 10 |  6 |  0 |    |
        53      | 37 | 32 | 27 | 22 | 17 | 12 |  7 |  3 |    |
        54      | 38 | 33 | 28 | 23 | 18 | 14 |  9 |  5 |  0 |

        55      | 39 | 34 | 29 | 25 | 20 | 15 | 11 |  6 |  2 |
        56      | 40 | 35 | 31 | 26 | 21 | 17 | 12 |  8 |  4 |
        57      | 41 | 36 | 32 | 27 | 23 | 18 | 14 | 10 |  5 |  1
        58      | 42 | 38 | 33 | 28 | 24 | 20 | 15 | 11 |  7 |  3
        59      | 43 | 39 | 34 | 30 | 25 | 21 | 17 | 13 |  9 |  5

        60      | 44 | 40 | 35 | 31 | 27 | 22 | 18 | 14 | 10 |  6
        61      | 45 | 40 | 36 | 32 | 28 | 24 | 20 | 16 | 12 |  8
        62      | 46 | 41 | 37 | 33 | 29 | 25 | 21 | 17 | 13 |  9
        63      | 47 | 42 | 38 | 34 | 30 | 26 | 22 | 18 | 14 | 11
        64      | 48 | 43 | 39 | 35 | 31 | 27 | 23 | 20 | 16 | 12


        Depression of wet-bulb thermometer (_t_-_t´_)

   Air |     |     |     |     |     |     |     |     |     |     |
  temp.| 1.0 | 2.0 | 3.0 | 4.0 | 5.0 | 6.0 | 7.0 | 8.0 | 9.0 |10.0 |11.0
   _t_ |     |     |     |     |     |     |     |     |     |     |
    65 |  95 |  90 |  85 |  80 |  75 |  70 |  66 |  62 |  57 | 53  | 48
    66 |  95 |  90 |  85 |  80 |  76 |  71 |  66 |  62 |  58 | 53  | 49
    67 |  95 |  90 |  85 |  80 |  76 |  71 |  67 |  62 |  58 | 54  | 50
    68 |  95 |  90 |  85 |  81 |  76 |  72 |  67 |  63 |  59 | 55  | 51
    69 |  95 |  90 |  86 |  81 |  77 |  72 |  68 |  64 |  59 | 55  | 51
       |     |     |     |     |     |     |     |     |     |     |
    70 |  95 |  90 |  86 |  81 |  77 |  72 |  68 |  64 |  60 | 56  | 52
    71 |  95 |  90 |  86 |  82 |  77 |  73 |  69 |  64 |  60 | 56  | 53
    72 |  95 |  91 |  86 |  82 |  78 |  73 |  69 |  65 |  61 | 57  | 53
    73 |  95 |  91 |  86 |  82 |  78 |  73 |  69 |  65 |  61 | 58  | 54
    74 |  95 |  91 |  86 |  82 |  78 |  74 |  70 |  66 |  62 | 58  | 54
       |     |     |     |     |     |     |     |     |     |     |
    75 |  96 |  91 |  87 |  82 |  78 |  74 |  70 |  66 |  63 | 59  | 55
    76 |  96 |  91 |  87 |  83 |  78 |  74 |  70 |  67 |  63 | 59  | 55
    77 |  96 |  91 |  87 |  83 |  79 |  75 |  71 |  67 |  63 | 59  | 56
    78 |  96 |  91 |  87 |  83 |  79 |  75 |  71 |  67 |  64 | 60  | 57
    79 |  96 |  91 |  87 |  83 |  79 |  75 |  71 |  68 |  64 | 60  | 57
       |     |     |     |     |     |     |     |     |     |     |
    80 |  96 |  91 |  87 |  83 |  79 |  76 |  72 |  68 |  64 | 61  | 57
    82 |  96 |  92 |  88 |  84 |  80 |  76 |  72 |  69 |  65 | 62  | 58
    84 |  96 |  92 |  88 |  84 |  80 |  77 |  73 |  70 |  66 | 63  | 59
    86 |  96 |  92 |  88 |  85 |  81 |  77 |  74 |  70 |  67 | 63  | 60
    88 |  96 |  92 |  88 |  85 |  81 |  78 |  74 |  71 |  67 | 64  | 61
       |     |     |     |     |     |     |     |     |     |     |
    90 |  96 |  92 |  89 |  85 |  81 |  78 |  75 |  71 |  68 | 65  | 62
    92 |  96 |  92 |  89 |  85 |  82 |  78 |  75 |  72 |  69 | 65  | 62
    94 |  96 |  93 |  89 |  86 |  82 |  79 |  75 |  72 |  69 | 66  | 63
    96 |  96 |  93 |  89 |  86 |  82 |  79 |  76 |  73 |  70 | 67  | 64
    98 |  96 |  93 |  89 |  86 |  83 |  79 |  76 |  73 |  70 | 67  | 64
       |     |     |     |     |     |     |     |     |     |     |
   100 |  96 |  93 |  90 |  86 |  83 |  80 |  77 |  74 |  71 | 68  | 65
   102 |  96 |  93 |  90 |  86 |  83 |  80 |  77 |  74 |  71 | 68  | 65
   104 |  97 |  93 |  90 |  87 |  84 |  80 |  77 |  74 |  72 | 69  | 66
   106 |  97 |  95 |  90 |  87 |  84 |  81 |  78 |  75 |  72 | 69  | 66
   108 |  97 |  93 |  90 |  87 |  84 |  81 |  78 |  75 |  72 | 70  | 67

   Air |      |      |      |      |      |      |      |      |
  temp.| 12.0 | 13.0 | 14.0 | 15.0 | 16.0 | 17.0 | 18.0 | 19.0 | 20.0
   _t_ |      |      |      |      |      |      |      |      |
   65  |  44  |  40  |  36  |  32  |  28  |  25  |  21  |  17  |  13
   66  |  45  |  41  |  37  |  33  |  29  |  26  |  22  |  18  |  15
   67  |  46  |  42  |  38  |  34  |  30  |  27  |  23  |  20  |  16
   68  |  47  |  43  |  39  |  35  |  31  |  28  |  24  |  21  |  17
   69  |  47  |  44  |  40  |  36  |  32  |  29  |  25  |  22  |  19
       |      |      |      |      |      |      |      |      |
   70  |  48  |  44  |  40  |  37  |  33  |  30  |  26  |  23  |  20
   71  |  49  |  45  |  41  |  38  |  34  |  31  |  27  |  24  |  21
   72  |  49  |  46  |  42  |  39  |  35  |  32  |  28  |  25  |  22
   73  |  50  |  46  |  43  |  40  |  36  |  33  |  29  |  26  |  23
   74  |  51  |  47  |  44  |  40  |  37  |  34  |  30  |  27  |  24
       |      |      |      |      |      |      |      |      |
   75  |  51  |  48  |  44  |  41  |  38  |  34  |  31  |  28  |  25
   76  |  52  |  48  |  45  |  42  |  38  |  35  |  32  |  29  |  26
   77  |  52  |  49  |  46  |  42  |  39  |  36  |  33  |  30  |  27
   78  |  53  |  50  |  46  |  43  |  40  |  37  |  34  |  31  |  28
   79  |  54  |  50  |  47  |  44  |  41  |  37  |  34  |  31  |  29
       |      |      |      |      |      |      |      |      |
   80  |  54  |  51  |  47  |  44  |  41  |  38  |  35  |  32  |  29
   82  |  55  |  52  |  49  |  46  |  43  |  40  |  37  |  34  |  31
   84  |  56  |  53  |  50  |  47  |  44  |  41  |  38  |  35  |  32
   86  |  57  |  54  |  51  |  48  |  45  |  42  |  39  |  37  |  34
   88  |  58  |  55  |  52  |  49  |  46  |  43  |  41  |  38  |  35
       |      |      |      |      |      |      |      |      |
   90  |  59  |  56  |  53  |  50  |  47  |  44  |  42  |  39  |  37
   92  |  59  |  57  |  54  |  51  |  48  |  45  |  43  |  40  |  38
   94  |  60  |  57  |  54  |  52  |  49  |  46  |  44  |  41  |  39
   96  |  61  |  58  |  55  |  53  |  50  |  47  |  45  |  42  |  40
   98  |  61  |  59  |  56  |  53  |  51  |  48  |  46  |  43  |  41
       |      |      |      |      |      |      |      |      |
  100  |  62  |  59  |  57  |  54  |  52  |  49  |  47  |  44  |  42
  102  |  63  |  60  |  57  |  55  |  52  |  50  |  47  |  45  |  43
  104  |  63  |  61  |  58  |  56  |  53  |  51  |  48  |  46  |  14
  106  |  64  |  61  |  59  |  56  |  54  |  51  |  49  |  47  |  45
  108  |  64  |  62  |  59  |  57  |  54  |  52  |  50  |  47  |  45

The prevailing impression seems to exist that when air is heated, it
loses its moisture. In reality, air that is heated only attains a
condition in which its capacity for containing moisture is increased.
If after being heated to a high degree--and is relatively very dry--the
air is reduced to its original temperature, the amount of moisture will
be the same as was originally contained. In heating houses with hot
air, the seemingly dry condition is usually due to temperature alone.
When a hot-air furnace is provided with the customary reservoir for
moistening the discharged air, it may be made to produce excellent
conditions of atmospheric humidity. The heated air readily absorbs the
water evaporated in the furnace from the water reservoir and enters
the rooms as relatively dry air but containing more moisture than the
outside air; when it has been reduced in temperature by mixing with the
cooler air of the house, its moisture content remains unaltered and at
the lower temperature its relative humidity is increased.

=Relative Humidity.=--Suppose that on a damp day the outside
temperature is 50° and that the atmosphere is 90 per cent. saturated.
The air that comes into the house at this temperature and humidity
is heated to 70°. The rise of temperature gives the air the property
of absorbing additional moisture so that the relative humidity which
was 90 per cent. is now much less. From the table relative humidity,
will be seen that at 50° temperature and 90 per cent. saturation the
air contains 3.67 grains of moisture. When the air is heated to 70°,
it still contains the original amount of moisture but its relative
humidity has decreased with the change of temperature. It is really
the amount of moisture present--3.67 grains--divided by the amount
necessary to saturate the air at 70°, which is 8 grains; this gives
approximately a relative humidity 40 per cent. saturation.

As the temperature goes lower, less and less moisture is required to
saturate the air. If saturated air at 0°F., which contains 0.48 grain
of water, is raised to 70°F.--where 8 grains of water is required for
saturation--the percentage of saturation would be 0.48/8 or 6 per cent.

=The Hygrometer.=--The instrument most commonly employed for
determining atmospheric humidity is the hygrometer. This appliance
is composed of two thermometers mounted in a frame with a vessel for
holding water. One of the thermometers is intended to register the
temperature of the air and is called the dry-bulb thermometer. The
bulb of the other--the wet-bulb thermometer--is covered with a piece
of cloth or other porous material which is kept saturated with water,
absorbed from the water holder. The dryness of the air is indicated
in the wet-bulb thermometer by the decline of temperature due to

The rate of evaporation from the wet-bulb covering will vary with
the humidity and if the air is very dry the wet-bulb thermometer
will register a temperature several degrees below that of the other
thermometer. If the air is saturated with moisture, no evaporation will
take place and the thermometers will read alike. The relative humidity
of the air as indicated by the readings of the thermometers is taken
directly from a humidity table. The table is made to suit any condition
of atmospheric humidity and the determinations require no calculation.

[Illustration: FIG. 157.--Hygrometer of U. S. Weather Bureau type; for
determining atmospheric humidity.]

Fig. 157 shows the U. S. Weather Bureau pattern hygrometer such as is
used at the weather stations. The wet-bulb thermometer has a muslin or
knitted silk covering which dips into a metal water cup as shown in the
figure. It is important that the covering of the wet bulb be kept in
good condition. The evaporation of the water from the covering leaves
in the meshes particles of solid matter that were held in solution in
the water. The accumulation of the solids ultimately prevent the water
from thoroughly wetting the wick.

An observation consists in reading the two thermometers and from the
difference between the wet-bulb reading and that of the dry-bulb, the
relative humidity is taken directly from the table. To illustrate,
suppose that the dry-bulb thermometer reads 60° and that the wet-bulb
reads 56°. The difference between the two readings is 4°. In the
table of relative humidity on page 202, 60° is found in the column
headed, Air temp. _t_, and opposite that number in the column headed
4 is 78, which indicates that under the observed conditions the air
is 78 per cent. saturated with moisture. This table is suited for
air temperatures from 35°F. to 80°F. and depressions of the wet-bulb
thermometer from 1°F. to 20°F. The table, therefore, has a range of
variations which will admit humidity determinations for all ordinary

[Illustration: FIG. 158.--The hygrodeik. A form of hygrometer in which
relative humidity is found directly from a diagram.]

=The Hygrodeik.=--In Fig. 158 is shown a form of hygrometer known as
a hygrodeik, by means of which atmospheric humidity may be determined
without the use of the tables. In the figure the wet-bulb and dry-bulb
thermometers are easily recognized. A glass water bottle _W_ is held
to the base of the instrument by spring clips which permit its removal
to be filled with water. Between the thermometers is a diagram chart
from which the atmospheric humidity is taken. An index arm, carrying a
movable pointer _P_, permits the instrument to be set for any observed
thermometer readings.

The index is really a graphical method of expressing the figures given
in the table on pages 202-203. In the picture the wet-bulb thermometer
reads 65°, the dry-bulb thermometer 77°. To determine the relative
humidity under these conditions the movable arm is swung to the left
and the pointer _P_ placed on the left-hand scale at the line 65°. The
arm is then swung to the right until the pointer touches the downward
curving line beginning at 77°, the dry-bulb reading. The lower end of
the arm _H_ now points to the relative humidity, where 52 per cent. is
indicated by the scale at the bottom of the index.

The same result is obtained from the table of Relative Humidity.
The readings of the thermometers in the figure give a difference in
temperature of 12°, the dry-bulb thermometer reads 77°. Referring this
data to the humidity table, the column marked 12, for the depression
of the wet-bulb thermometer and opposite 77° in the air temperature
column, is found 53 which indicates the per cent. of saturation. The
hygrodeik gives further the temperature of the dew-point, on the scale
to the right; and the absolute humidity may be found by following the
upward curving line nearest the pointer, at the end of which line is
given the value in grains of moisture per cubic foot. The hygrodeik
or other instrument of the kind is very largely used in places where
relative humidity is regularly observed by those of limited experience,
as in school-rooms, auditoriums, etc. Such records are not intended
to be perfectly accurate and the readings of the hygrodeik are very
well-suited for the purpose.

In using the hygrometer and the hygrodeik the instruments are
stationary; they are usually hung on the wall in a convenient location
for observation and are placed to avoid accidental drafts in order
that the conditions surrounding the observation may be the same at all
times. The evaporation which takes place from the wet bulb is due to
natural convection and does not always reach the maximum amount. The
evaporation is furthermore influenced by accidental variations and
consequently the results cannot be considered exact.

[Illustration: FIG. 159.--Psychrometer of U. S. Weather Bureau type;
for accurate determination of atmospheric humidity.]

Under conditions that demand more exact humidity records than are
obtainable with hygrometer, the psychrometer furnishes means of making
more accurate observation. The psychrometer shown in Fig. 159 is of
the form used by the U. S. Weather Department. Like the hygrometer, it
is composed of a wet-bulb and a dry-bulb thermometer but no water cup
is attached to the instrument for moistening the wick of the wet bulb.
When ready for use the wick is wet with water before each observation.

The greater accuracy to be attained by the use of this instrument is
on account of the maximum evaporation which is obtained from the wet
bulb for any atmospheric condition. The evaporation which takes place
from the wet-bulb thermometer in quiet air is not so great as that
which occurs if the same air is in motion. In moving air, however,
there is a certain maximum rate beyond which no further evaporation
will take place.

The motion of the air may be produced either by blowing on the bulb
with a fan or air blast, or by whirling the thermometer. With the
psychrometer the latter method is used. This instrument is provided
with a handle which is pivoted to the frame and about which it is swung
to produce a maximum evaporation from the wick. When a motion of the
air is attained sufficient to produce a saturated atmosphere about the
bulb, the temperature will remain constant.

A velocity of air or the motion of the wet-bulb thermometer 10 feet
per second is that usually taken as the rate for observation and the
swinging is kept up 3 or 4 minutes or until the temperature of the
wet-bulb thermometer remains stationary.

[Illustration: FIG. 160.--Dial hygrometer.]

Then the temperature of each thermometer is read and the humidity
found in the table. Relative humidity determinations may be made at
temperatures below the freezing point if sufficient precaution is taken
in the observations. When the instrument is not in use, it is kept in
the metallic case shown in the picture, to protect it from injury.

=Dial Hygrometers.=--Various forms of hygrometers are in use, in
which a pointer is intended to indicate on a dial the percentage of
atmospheric humidity. That shown in Fig. 160 is one of the common
forms. Instruments of this kind depend for their action on the
absorptive property of catgut or other materials that are sensitive to
the moisture changes of the air.

These instruments give fairly accurate readings in a small range for
a limited time, but they are apt to go out of adjustment from causes
that cannot be controlled. Unless they are occasionally compared with a
standard humidity determination, their readings cannot be relied upon
for definite amounts of atmospheric moisture.

=The Swiss Cottage “Barometer.”=--Fig. 161 is one of the instruments
of absorptive class that are sometimes used as weather indicators. The
images which occupy the openings in the cottage are so arranged that
with the approach of damp weather the man comes outside and at the same
time the woman moves back into the house. In fair weather the reverse
movement takes place. The figures are mounted on the opposite ends of a
light stick which is fastened to an upright pillar. The movement of the
images is caused by the change in length of a piece of catgut which is
secured to the pillar and also to the frame of the house. Any change in
atmospheric humidity causes a contraction or elongation of the catgut
which moves the pillar and with it the images.

Since stormy weather is accompanied by a high degree of humidity and
fair weather is attended with dry atmosphere, the movement of the
images indicates in some degree the weather changes; but the device is
not in any way influenced by atmospheric pressure and hence is not a

[Illustration: FIG. 161.--Swiss cottage “Barometer.” This device is
arranged to show the condition of atmospheric humidity by the movement
of the images. It is not really a barometer.]

=Dew-point.=--Dew is formed whenever falling temperature of the
air passes the point where saturation occurs. The reduction of the
temperature of air raises the relative humidity because of the
diminished capacity to contain moisture. As the temperature declines
there will come a point at which the air is saturated and any further
decrease of temperature will cause supersaturation. At this point the
moisture will be deposited on the cooler surfaces in the form of drops.
The temperature at which dew begins to form is known as the dew-point.
The sweating of cold water pipes, the dew that forms on a water glass
and other relatively cold surfaces is caused by a temperature below the
dew-point of the air.


  Dew-point in degrees Fahrenheit, barometer pressure 29 inches
    Air | Vapor |Depression of wet-bulb thermometer (_t_-_t´_)
   temp.| press.|-----+-----+-----+-----+-----+-----+-----+-----
    _t_ |  _e_  | 1.0 | 2.0 | 3.0 | 4.0 | 5.0 | 6.0 | 7.0 | 8.0
    30  | 0.164 | 27  | 25  | 22  | 18  | 14  |  9  | +3  | -5
    31  | 0.172 | 29  | 26  | 23  | 20  | 16  | 11  |  5  | -2
    32  | 0.180 | 30  | 27  | 24  | 21  | 17  | 13  |  8  | +1
    33  | 0.187 | 31  | 28  | 25  | 22  | 19  | 15  | 10  |  3
    34  | 0.195 | 32  | 29  | 27  | 24  | 20  | 16  | 12  |  6
        |       |     |     |     |     |     |     |     |
    35  | 0.203 | 33  | 30  | 28  | 25  | 22  | 18  | 14  |  8
    36  | 0.211 | 34  | 31  | 29  | 26  | 23  | 20  | 15  | 11
    37  | 0.219 | 35  | 32  | 30  | 27  | 24  | 21  | 17  | 13
    38  | 0.228 | 36  | 33  | 31  | 28  | 26  | 23  | 19  | 14
    39  | 0.237 | 37  | 34  | 32  | 29  | 27  | 24  | 21  | 16
        |       |     |     |     |     |     |     |     |
    40  | 0.247 | 38  | 35  | 33  | 31  | 28  | 25  | 22  | 18
    41  | 0.256 | 39  | 37  | 34  | 32  | 29  | 26  | 23  | 20
    42  | 0.266 | 40  | 38  | 35  | 33  | 30  | 28  | 25  | 21
    43  | 0.277 | 41  | 39  | 36  | 34  | 31  | 29  | 26  | 23
    44  | 0.287 | 42  | 40  | 38  | 35  | 32  | 30  | 27  | 24
        |       |     |     |     |     |     |     |     |
    45  | 0.298 | 43  | 41  | 39  | 36  | 34  | 31  | 29  | 26
    46  | 0.310 | 44  | 42  | 40  | 37  | 35  | 32  | 30  | 27
    47  | 0.322 | 45  | 43  | 41  | 39  | 36  | 34  | 31  | 28
    48  | 0.334 | 46  | 44  | 42  | 40  | 37  | 35  | 32  | 30
    49  | 0.347 | 47  | 45  | 43  | 41  | 39  | 36  | 34  | 31
        |       |     |     |     |     |     |     |     |
    50  | 0.360 | 48  | 46  | 44  | 42  | 40  | 37  | 35  | 32
    51  | 0.373 | 49  | 47  | 45  | 43  | 41  | 39  | 36  | 34
    52  | 0.387 | 50  | 48  | 46  | 44  | 42  | 40  | 37  | 35
    53  | 0.402 | 51  | 49  | 47  | 45  | 43  | 41  | 39  | 36
    54  | 0.417 | 52  | 50  | 49  | 47  | 44  | 42  | 40  | 38
    55  | 0.432 | 53  | 52  | 50  | 48  | 46  | 43  | 41  | 39
    56  | 0.448 | 54  | 53  | 51  | 49  | 47  | 45  | 43  | 40
    57  | 0.465 | 55  | 54  | 52  | 50  | 48  | 46  | 44  | 42
    58  | 0.482 | 56  | 55  | 53  | 51  | 49  | 47  | 45  | 43
    59  | 0.499 | 57  | 56  | 54  | 52  | 50  | 48  | 46  | 44
        |       |     |     |     |     |     |     |     |
    60  | 0.517 | 58  | 57  | 55  | 53  | 51  | 49  | 47  | 45
    61  | 0.536 | 59  | 58  | 56  | 54  | 52  | 51  | 49  | 46
    62  | 0.555 | 60  | 59  | 57  | 55  | 54  | 52  | 50  | 48
    63  | 0.575 | 61  | 60  | 58  | 56  | 55  | 53  | 51  | 49
    64  | 0.595 | 62  | 61  | 59  | 58  | 56  | 54  | 52  | 50
        |       |     |     |     |     |     |     |     |
    65  | 0.616 | 63  | 62  | 60  | 59  | 57  | 55  | 53  | 51
    66  | 0.638 | 64  | 63  | 61  | 60  | 58  | 56  | 54  | 53
    67  | 0.661 | 65  | 64  | 62  | 61  | 59  | 57  | 56  | 54
    68  | 0.684 | 67  | 65  | 63  | 62  | 60  | 58  | 57  | 55
    69  | 0.707 | 68  | 66  | 64  | 63  | 61  | 60  | 58  | 56
        |       |     |     |     |     |     |     |     |
    70  | 0.732 | 69  | 67  | 66  | 64  | 62  | 61  | 59  | 57
    71  | 0.757 | 70  | 68  | 67  | 65  | 63  | 62  | 60  | 58
    72  | 0.783 | 71  | 69  | 68  | 66  | 65  | 63  | 61  | 60
    73  | 0.810 | 72  | 70  | 69  | 67  | 66  | 64  | 62  | 61
    74  | 0.838 | 73  | 71  | 70  | 68  | 67  | 65  | 64  | 62
        |       |     |     |     |     |     |     |     |
    75  | 0.866 | 74  | 72  | 71  | 69  | 68  | 66  | 65  | 63
    76  | 0.896 | 75  | 73  | 72  | 70  | 69  | 67  | 66  | 64
    77  | 0.926 | 76  | 74  | 73  | 71  | 70  | 68  | 67  | 65
    78  | 0.957 | 77  | 75  | 74  | 72  | 71  | 69  | 68  | 66
    79  | 0.989 | 78  | 76  | 75  | 73  | 72  | 70  | 69  | 67
        |       |     |     |     |     |     |     |     |
    80  | 1.022 | 79  | 77  | 76  | 75  | 73  | 72  | 70  | 69

    Air | Vapor |Depression of wet-bulb thermometer (_t_-_t´_)
   temp.| press.|-----+-----+-----+-----+-----+-----+-----+-----
    _t_ |  _e_  | 9.0 |10.0 |11.0 |12.0 |13.0 |14.0 |15.0 |16.0
    30  | 0.164 | -20 |     |     |     |     |     |     |
    31  | 0.172 | -14 | -50 |     |     |     |     |     |
    32  | 0.180 |  -9 | -29 |     |     |     |     |     |
    33  | 0.187 |  -5 | -20 |     |     |     |     |     |
    34  | 0.195 |  -2 | -14 | -50 |     |     |     |     |
        |       |     |     |     |     |     |     |     |
    35  | 0.203 |  +1 |  -8 | -28 |     |     |     |     |
    36  | 0.211 |   4 |  -4 | -19 |     |     |     |     |
    37  | 0.219 |   7 |  -1 | -12 | -44 |     |     |     |
    38  | 0.228 |   9 |  +3 |  -7 | -25 |     |     |     |
    39  | 0.237 |  12 |   6 |  -3 | -16 |     |     |     |
        |       |     |     |     |     |     |     |     |
    40  | 0.247 |  14 |   8 |  +1 | -10 | -35 |     |     |
    41  | 0.256 |  16 |  11 |   4 |  -5 | -21 |     |     |
    42  | 0.266 |  17 |  13 |   7 |  -1 | -13 | -59 |     |
    43  | 0.277 |  19 |  15 |  10 |  +3 |  -7 | -28 |     |
    44  | 0.287 |  21 |  17 |  12 |   6 |  -2 | -17 |     |
        |       |     |     |     |     |     |     |     |
    45  | 0.298 |  22 |  19 |  14 |   8 |  +2 |  -9 | -37 |
    46  | 0.310 |  24 |  20 |  16 |  11 |   5 |  -4 | -20 |
    47  | 0.322 |  25 |  22 |  18 |  13 |   8 |  +0 | -12 |-53
    48  | 0.334 |  27 |  23 |  20 |  15 |  10 |  +4 |  -6 |-25
    49  | 0.347 |  28 |  25 |  21 |  17 |  13 |   7 |  -2 |-15
        |       |     |     |     |     |     |     |     |
    50  | 0.360 |  29 |  27 |  23 |  19 |  15 |   9 |  +2 | -8
    51  | 0.373 |  31 |  28 |  25 |  21 |  17 |  12 |   6 | -3
    52  | 0.387 |  32 |  29 |  26 |  23 |  19 |  14 |   9 | +1
    53  | 0.402 |  34 |  31 |  28 |  24 |  21 |  16 |  11 |  5
    54  | 0.417 |  35 |  32 |  29 |  26 |  23 |  19 |  14 |  8
    55  | 0.432 |  36 |  34 | 31  | 28  | 24  | 21  | 16  | 11
    56  | 0.448 |  38 |  35 | 32  | 29  | 26  | 23  | 19  | 14
    57  | 0.465 |  39 |  36 | 34  | 31  | 28  | 24  | 21  | 16
    58  | 0.482 |  40 |  38 | 35  | 32  | 29  | 26  | 22  | 18
    59  | 0.499 |  42 |  39 | 37  | 34  | 31  | 28  | 24  | 20
        |       |     |     |     |     |     |     |     |
    60  | 0.517 |  43 |  41 | 38  | 35  | 32  | 29  | 26  | 22
    61  | 0.536 |  44 |  42 | 39  | 37  | 34  | 31  | 28  | 24
    62  | 0.555 |  46 |  43 | 41  | 38  | 35  | 32  | 30  | 26
    63  | 0.575 |  47 |  45 | 42  | 40  | 37  | 34  | 31  | 28
    64  | 0.595 |  48 |  46 | 44  | 41  | 38  | 36  | 33  | 30
        |       |     |     |     |     |     |     |     |
    65  | 0.616 |  49 |  47 | 45  | 43  | 40  | 37  | 34  | 31
    66  | 0.638 |  51 |  48 | 46  | 44  | 42  | 39  | 36  | 33
    67  | 0.661 |  52 |  50 | 48  | 45  | 43  | 40  | 38  | 35
    68  | 0.684 |  53 |  51 | 49  | 47  | 44  | 42  | 39  | 36
    69  | 0.707 |  54 |  52 | 50  | 84  | 46  | 43  | 41  | 38
        |       |     |     |     |     |     |     |     |
    70  | 0.732 |  55 |  53 | 51  | 49  | 47  | 45  | 42  | 40
    71  | 0.757 |  57 |  55 | 53  | 51  | 49  | 46  | 44  | 41
    72  | 0.783 |  58 |  56 | 54  | 52  | 50  | 48  | 45  | 43
    73  | 0.810 |  59 |  57 | 55  | 53  | 51  | 49  | 47  | 44
    74  | 0.838 |  60 |  58 | 56  | 54  | 53  | 50  | 48  | 46
        |       |     |     |     |     |     |     |     |
    75  | 0.866 |  61 |  60 | 58  | 56  | 54  | 52  | 50  | 47
    76  | 0.896 |  62 |  61 | 59  | 57  | 55  | 53  | 51  | 49
    77  | 0.926 |  64 |  62 | 60  | 58  | 56  | 54  | 52  | 50
    78  | 0.957 |  65 |  63 | 61  | 59  | 58  | 56  | 54  | 52
    79  | 0.989 |  66 |  64 | 62  | 61  | 59  | 57  | 55  | 53
        |       |     |     |     |     |     |     |     |
    80  | 1.022 |  67 |  65 | 64  | 62  | 60  | 58  | 56  | 54

The temperature at which dew forms will depend on the amount of
moisture present in the air, but with a definite humidity and air
pressure it will always occur at the same temperature. If the dew-point
is above freezing, the dew will form as drops of water, but if it is
at or slightly below the freezing point, the dew will appear as frost.
_White frost_ is formed when the dew-point is only a few degrees
below the freezing point. _A Black frost_ occurs when the atmospheric
humidity is so low that dew does not form until the temperature is much
below the freezing point.

=To Determine the Dew-point.=--The dew-point may be found by a number
of methods, usually described in works on physics but practical
determinations are made with a hygrometer or psychrometer and a
dew-point table. Accurate determinations must be made by the use of the
psychrometer; those made by the hygrometer are approximate. Suppose the
reading of the dry-bulb thermometer is 68 and that this is designated
as _t_; at the time the wet-bulb temperature is 57 and is called _t´_.
The depression of the wet bulb for these temperatures (_t_-_t´_) is
11°. In the dew-point table above is found in the dry-bulb column,
opposite this number in the column headed 11--under depression of the
wet-bulb thermometer--is 49, which is the dew-point for the observed

As another illustration, suppose the dry bulb of the psychrometer marks
65° and the wet bulb indicates 56°F.; then 65-56 equals 9° of the cold
produced by evaporation. The dew-point is determined in exactly the
same way as with the hygrometer. Opposite 65, in the dry-bulb column
of the dew-point table, under the column of differences marked 9, is
found the dew-point for the observed conditions. This is 49° at which
temperature dew will begin to form.

=Frost Prediction.=--The formation of dew is always attended with a
liberation of heat--the heat of vaporization--which tends to check the
further decline of temperature. The heat thus developed is usually
sufficient to prevent the fall of temperature beyond a very few
degrees, but at times when there is little moisture in the air the
fall of several degrees of temperature is necessary before the heat
liberated by the forming dew balances the heat lost by radiation and
the temperature remains stationary.

This condition of things was pointed out many years ago by Tyndall, who
in his book on “Heat” states: “The removal for a single summer’s night
of the aqueous vapor which covers England would be attended by the
destruction of every plant which a freezing temperature would kill.”

The frosts of late spring and early fall which occur at times of dry
air and cloudless sky are often caused by local conditions that are
not forecasted by the weather department and often may be successfully

At the time of suspected frost, the temperature of the dew-point in
relation to the freezing point determines the probability of a freezing
temperature. If the dew-point occurs at 10° or more above the freezing
point there will be little danger of a killing frost. As the difference
in temperature between the dew-point and the frost point decreases,
the danger of frost increases. If the dew-point falls at the freezing
point, frost is a certainty.

In using the table on page 214, the open diagonal line may be
considered the danger line and any dew-point falling below the
temperature thus indicated will be considered dangerously near the
frost point. This table differs from the other dew-point table only
in the range of temperature. The dew-point is found in exactly the
same way as before. In the use of the psychrometer and table as a
means of frost prediction it is first necessary to make a reading of
the wet-bulb and dry-bulb temperature described above. The dry-bulb
reading is found in the left-hand column of the table; then follow the
horizontal line opposite the figure, till the perpendicular column
is reached indicating the difference in reading between the dry and
wet bulb. The number at the meeting will be the temperature of the
dew-point. For example, suppose the dry bulb stands at 65° and the
wet bulb at 55°, the difference being 10° and dew-point under these
conditions will be 47°.

If the dew-point is 10° or more above the freezing point there is
no danger of a frost, but if the conditions are such as to give a
temperature difference less than 10° above the freezing point there
would be danger. If the dew-point falls below the open diagonal line of
the table there is danger and that danger increases as the difference
in degrees between the freezing point and the dew-point becomes less.

As another illustration, suppose that at sunset at the time of
suspected frost the dry-bulb thermometer read 54 and the depression of
the wet bulb showed 10°. Referring to the table it will be seen that
for these conditions the dew-point falls at 33 which is only 1° above
the freezing point. It is highly probable that frost would form.


                  Depression of the wet-bulb thermometer
  Dry- |    |    |    |    |    |    |    |    |    |    |    |    |
  bulb |  1 |  2 |  3 |  4 |  5 |  6 |  7 |  8 |  9 | 10 | 11 | 12 | 13
  temp.|    |    |    |    |    |    |    |    |    |    |    |    |
   70  | 69 | 67 | 66 | 64 | 62 | 61 | 59 | 57 | 55 | 53 | 51 | 49 | 47
   69  | 68 | 66 | 64 | 63 | 61 | 59 | 58 | 56 | 54 | 52 | 50 | 48 | 46
   68  | 67 | 65 | 63 | 62 | 60 | 58 | 57 | 55 | 53 | 51 | 49 | 46 | 44
   67  | 66 | 64 | 62 | 61 | 59 | 57 | 55 | 54 | 52 | 50 | 47 | 45 | 43
   66  | 64 | 63 | 61 | 60 | 58 | 56 | 54 | 52 | 50 | 48 | 46 | 44 |
   65  | 63 | 62 | 60 | 59 | 57 | 55 | 53 | 51 | 49 | 47 | 45 | 42 | 41
   64  | 62 | 61 | 59 | 57 | 56 | 54 | 52 | 50 | 48 | 46 | 43 |    | 40
   63  | 61 | 60 | 58 | 56 | 55 | 53 | 51 | 49 | 47 | 44 | 42 | 41 | 38
   62  | 60 | 59 | 57 | 55 | 53 | 52 | 50 | 48 | 45 | 43 |    | 39 | 37
   61  | 59 | 58 | 56 | 54 | 52 | 50 | 48 | 46 | 44 | 42 | 41 | 38 | 35
   60  | 58 | 57 | 55 | 53 | 51 | 49 | 47 | 45 | 43 |    | 39 | 36 | 33
   59  | 57 | 56 | 54 | 52 | 50 | 48 | 46 | 44 |    | 40 | 38 | 43 | 32
   58  | 56 | 55 | 53 | 51 | 49 | 47 | 45 | 42 | 41 | 39 | 36 | 33 | 30
   57  | 55 | 54 | 52 | 50 | 48 | 46 | 44 |    | 40 | 37 | 35 | 31 | 28
   56  | 54 | 53 | 51 | 49 | 47 | 44 | 42 | 41 | 39 | 36 | 33 | 30 | 26
   55  | 53 | 52 | 50 | 48 | 46 | 43 |    | 40 | 37 | 34 | 31 | 28 | 25
   54  | 52 | 50 | 49 | 46 | 44 | 42 | 41 | 39 | 36 | 33 | 30 | 27 | 23
   53  | 51 | 49 | 47 | 45 | 43 |    | 40 | 37 | 34 | 31 | 28 | 25 | 20
   52  | 50 | 48 | 46 | 44 | 42 | 41 | 38 | 36 | 33 | 30 | 27 | 23 | 18
   51  | 49 | 47 | 45 | 43 |    | 40 | 37 | 34 | 31 | 28 | 25 | 21 | 16
   50  | 48 | 46 | 44 | 42 | 41 | 38 | 36 | 33 | 30 | 27 | 23 | 19 | 14
   49  | 47 | 45 | 43 |    | 40 | 37 | 34 | 31 | 28 | 25 | 21 | 17 | 11
   48  | 46 | 44 | 42 | 41 | 38 | 36 | 33 | 30 | 27 | 23 | 19 | 14 |  9
   47  | 45 | 43 |    | 40 | 37 | 35 | 32 | 29 | 25 | 22 | 17 | 12 |  6
   46  | 44 | 42 | 41 | 39 | 36 | 33 | 30 | 27 | 24 | 20 | 15 | 10 |  3
   45  | 43 |    | 40 | 37 | 35 | 32 | 29 | 26 | 22 | 18 | 13 |  7 | -1
   44  | 42 | 41 | 39 | 36 | 33 | 30 | 27 | 24 | 20 | 16 | 11 |  4 | -5
       |    | 40 | 37 | 35 | 32 | 29 | 26 | 23 | 19 | 14 |  8 |  1 | -9
   43  | 41 | 39 | 36 | 34 | 31 | 28 | 25 | 21 | 17 | 12 |  6 | -2 |-15
   42  | 40 | 38 | 35 | 33 | 29 | 26 | 23 | 19 | 15 |  9 |  3 | -6 |-22
   41  | 39 | 36 | 34 | 31 | 28 | 25 | 22 | 17 | 13 |  7 |  0 |-11 |-32
   40  | 38 | 35 | 33 | 30 | 27 | 24 | 20 | 16 | 11 |  4 | -4 |-16 |-74
   39  | 37 | 34 | 32 | 29 | 26 | 22 | 18 | 14 |  8 |  2 | -8 | 23 |
   38  | 36 | 33 | 31 | 28 | 24 | 21 | 17 | 12 | -6 | -1 |-12 |-35 |

=Prevention of Frost.=--From the discussion of frost formation it is
evident that, the temperature of the dew-point being the determining
factor in its probable occurrence, any expedient that may be used
either to increase the humidity or to conserve the radiation of heat
would prevent a dangerous decline of temperature. Frost prevention is
practised in all fruit-growing regions and the method pursued depends
on the kind of vegetation to be protected.

In the protection of orchards the use of smudge pots are probably the
commonest means for preventing the loss of heat. The object is to
create a cloud of smoke over and about the orchard so that it forms a
protective covering which prevents the escape of the heat.

In the case of a light frost--that is, where the temperature falls only
a few degrees below the frost point--the plants in small gardens and
flower beds may be prevented from freezing by liberal sprinkling with
water. This is done to raise the humidity of the atmosphere surrounding
the vegetation. Most vegetation withstands the temperature at the
freezing point without particular injury, and the freezing of part of
the water liberates heat in sufficient quantity to prevent a further
decline of temperature. This heat liberated on the freezing of water is
described in physics as the heat of fusion and in changing part of the
water into ice sufficient heat is liberated to check the further fall
of temperature.

=Humidifying Apparatus.=--Opportunity for adding moisture, in the
desired quantity, to the air of the average dwelling is limited to the
evaporation of water in the heating plant, from vessels attached to the
radiators or that which goes on in the kitchen. Household humidifying
plants are within the range of possibility but there is not yet
sufficient demand for their use to make attractive their manufacture.

In the hot-air furnace a water reservoir is usually a part of the
chamber in which the air supply is heated. The water in the reservoir
is heated to a greater or lesser degree, depending on the temperature
of the furnace and vaporized both by heat and by the constantly
changing air.

In the use of a steam plant or hot-water heating plant the opportunity
of humidifying the air is very limited. One method is that of
suspending water tanks to the back of the radiators from which water
is vaporized. While this method is fairly efficient as a humidifier it
is inconvenient and therefore apt to be neglected. In houses heated by
stoves there are sometimes water urns attached to the top of the frame
which are intended for the evaporation of water but as a rule they are
not of sufficient size to be of appreciable value.

The quantity of water required to humidify the air of a house will
depend _first_, on the temperature and humidity of the outside air;
_second_, on the cubic contents of the building; _third_, on the rate
of change of air in the building. If the ventilation is good the rate
of atmospheric change is rapid and the amount of water in consequence
must be correspondingly increased.

The data included in the following table showing the relative humidity
and amount of water required were taken from a seven-room frame
dwelling in Fargo, N. D., during particularly severe winter weather.
The relative humidity determinations were made with a hygrodeik each
day at noon. The house was heated by a hot-air furnace arranged to take
its air supply from the outside.

The air supply is recorded under Cold-air intake. The furnace was
provided with a water pan for humidifying the air supply. The amount of
water evaporated each day is recorded in the column headed Evap. in 24
hours. The outside temperature ranged from -12°F. to -21°F. The weather
was clear and calm except the last day, Jan. 12, which was windy. The
higher humidity on that day was no doubt due to the greater amount of
heat required from the furnace and the consequent evaporation of the
water from the water pan.

The humidity determinations made by a hygrodeik, as before explained,
are only approximately correct but sufficiently exact for practical
purposes. The temperature is given in degrees Fahrenheit.

In the table it will be noticed that the outside air was used only a
part of the time because of the severity of the weather. Attention is
called to the quantity of water required to keep the humidity at the
amount shown. This averages 27-1/2 quarts per day. At the time these
observations were made the physics lecture-room at the North Dakota
Agricultural College averaged 18 to 20 per cent. saturation during
class hours, with observations made from a similar instrument. This is
a steam-heated room with only accidental means of adding water to the
air. The result was an atmosphere 3-1/2 per cent. above that of Death


            Readings taken at 12 o’clock noon each day

          | Temp. |Wet |Dry |   Per   |  Evap. In   |
    Date  |outside|bulb|bulb|  cent.  |  24 hours   | Cold-air intake
          |       |    |    |saturated|quarts pints |
  Dec. 13 |  -13  | 54°| 63°|   53    |             | Closed 8 a.m.
  Dec. 14 |  -18  | 55 | 66 |   47    |             | Open
  Dec. 15 |  -20  | 57 | 68 |   49    |  21         | Closed 7 a.m.
  Dec. 16 |  -18  | 57 | 67 |   51    |  20   1     | Closed 7 a.m.
  Dec. 17 |  -22  | 58 | 69 |   48    |  18   1     | Closed 7 a.m.
  Dec. 18 |  -16  | 55 | 65 |   51    |  17   1½    | Closed 6:30 a.m.
  Dec. 19 |  -10  | 57 | 68 |   47    |  20   1     | Closed 8 a.m.
  Dec. 20 |    0  | 59 | 70 |   49    |  13    ¾    | Not open at night
  Jan. 8  |  -12  | 58 | 71 |   43    |  18         | Closed
  Jan. 9  |  -17  | 57 | 71 |   39    |  25         | Open 24 hours
  Jan. 10 |  -16  | 58 | 69 |   45    |  27   1     | Open 10 hours
  Jan. 11 |  -21  | 60 | 75 |   40    |  30         | Closed
  Jan. 12 |  -15  | 60 | 73 |   46    |  30         | Closed

The amounts of water evaporated may seem large to those who are
unaccustomed to quantitatively consider problems in ventilation but
the small amount of water in the air at -21° must produce a very dry
atmosphere when it is raised to 70° in temperature.

The amount of moisture in air at 20°F. and at 80 per cent. humidity is
only 1.58 grains to the cubic foot. If this air is now raised to 70°
the moisture will still be 1.58 grains where there should be 4 grains
of water to make 50 per cent. humidity. It therefore will require the
addition of practically 2.42 grains of water for each cubic foot of
entering air in order to bring it up to 50 per cent. humidity.

In a case with the above conditions of atmosphere, suppose it is
desired to know the amount of water that would be taken up in
humidifying the air for a school-room of size to accommodate 40 pupils.
The prescribed quantity of air for this purpose is 30 cubic feet per
minute for each pupil. The air is to be maintained at a humidity 50 per
cent. saturated. The problem will be one of simple arithmetic. If each
pupil is to receive 30 cubic feet of air per minute or 1800 cubic feet
per hour, the 40 pupils receiving 1800 cubic feet per hour will require
40 × 1800 = 72,000 cubic feet of air per hour. To each cubic foot of
the air is to be added 2.74 grains of water, 72,000 × 2.42 = 164,240
grains of water. Reducing this to pounds, 164,240 ÷ 7000 = 23.46 pounds
or 2.77 gallons of water per hour.

In practice the room will show a higher amount than 50 per cent.
humidity with this addition of the amount of water, because of the
water vapor that is exhaled from the lungs of the pupils. That a
considerable amount of water vapor is added to the atmosphere by breath
exhalation is made evident from the moisture condensed by breathing
on a cold pane of glass. In any unventilated room occupied by a
considerable number of people the humidity is thus increased a very
noticeable amount.

The change in humidity of the air in a closed room filled with people
is very pronounced. The constant exhalation of moisture from the lungs
is sufficient to saturate the air in a short time. The heavy atmosphere
of overcrowded, unventilated rooms is due to moisture exhalation,
body odors and increased carbonic acid gas. As the humidity of the
atmosphere is increased a sensation of uncomfortable warmth is the
result of the lesser evaporation.



The purity of air in any habitable enclosure is determined by the
amount of CO₂ (Carbonic acid gas) included in its composition. The
process of ventilation is that of adding fresh air to the impure
atmosphere of houses, until a desirable quality is attained. In the
opinion of hygienists, when air does not exceed 6 to 8 parts of CO₂, by
volume in 10,000, the ventilation is desirable. Ordinary outdoor air
contains about 4 parts of CO₂ to 10,000, while very bad air may contain
as high as 80 parts to the same quantity. The quantity of air required
for the ventilation of a building is determined by the number of people
to be provided. The amount of air required per individual per hour
necessary to produce a desired condition of ventilation is determined
by adopting a standard of purity to suit the prevailing circumstances.

In hospitals where pure air is considered of greatest importance 4000
and 5000 cubic feet per inmate per hour is not uncommon. The practice
of supplying 30 cubic feet of air per person per minute (1800 cubic
feet per hour) seems to fulfill the average requirements. It is the
amount commonly specified for school-rooms.

The quantity of fresh air required per person to insure good
ventilation will depend on the type of building to be supplied and
varies somewhat with different authorities. The De Chaumont standard
is that of 1 cubic foot of air per second or 3600 cubic feet per hour,
for each person to be accommodated. De Chaumont assumed a condition
of purity which will permit less than 2 parts in 10,000 of CO₂ over
that carried by country air. In considering the same problem from
the basis of permissible CO₂, if 6 parts of CO₂ in 10,000 represents
purity of the required air, then 3000 cubic feet per person per hour
is necessary. Likewise, the varying amounts for different degrees of
purity are given by Kent in the following table. The upper line gives
the permissible number of parts of CO₂ per 10,000, while below each
factor appears the number of cubic feet of air required per hour for
each person supplied.

    6  |  7  |  8  |  9  | 10  | 15| 20| = Parts of CO₂ per 10,000
  3,000|2,000|1,500|1,200|1,000|545|375| = Cubic feet of pure air
       |     |     |     |     |   |   |   per hour

It is generally recognized, that it is possible to live under
conditions where no attempt is made to change the air in a building.
It is also an established fact that the only preventive and cure for
tuberculosis is that of living constantly in an atmosphere of the
purest air. The greatest attainable degree of health is enjoyed by
those who live in the open air, because oxidation is one of the most
efficient forms of prevention and elimination of disease, and an
abundance of pure air is the only assured means of sufficient oxidation.

The De Chaumont standard is intended to represent the limit beyond
which the sense of smell fails to detect body odors or “closeness”
in an occupied room. The amount of CO₂ that air contains is not an
absolute index of its purity, but it gives a standard under ordinary
conditions, makes possible the requirement of a definite quantity of
air. If it were possible to express the amount of oxygen contained in
the atmosphere, the same relative condition might be attained.

The ordinary man exhales 0.6 cubic foot of CO₂ per hour. Some forms of
lighting apparatus produces this gas in greater amounts. The ordinary
kerosene lamp gives out 1 cubic foot of CO₂ per hour. A gas light using
5 cubic feet of gas per hour produces 3.75 cubic feet of CO₂ in the
same time. Any form of combustion permitting the products to escape
into the air of the room tends to lower the quality of the atmosphere
by adding to its content of CO₂.

The prevailing impression that impure air is heavy and settles to
the floor is erroneous. Impurities in the form of gases and vapors
(principally carbonic acid gas and odors) diffuse throughout the
entire space, and the entering fresh air tends to dilute the entire

As a quantative problem, ventilation consists in admitting pure air
into an impure atmosphere in amount to give a definite degree of
purity. This is accomplished by admitting sufficient air to completely
change the atmosphere at stated intervals, or to provide a definite
quantity for each inhabitant.

The methods by which ventilation may be accomplished will depend on the
type of building to be ventilated and the apparatus it is possible to
use. When the use of mechanical ventilation appliances are permissible,
any desired degree of atmospheric purity may be maintained at all
times, under any condition of climate or change of weather.

In buildings where mechanical ventilation cannot be considered as that
of the average dwelling, the problem is one of producing an average
condition of reasonably pure air by natural convection. In the average
dwelling, ventilation is accomplished by the natural draft produced in
chimneys or air flues, by partially opened windows and by the force
produced by the movement of the outside air. In some buildings a better
condition of ventilation is attained by ordinary means than at first
sight seems possible.

The fact that it is difficult to keep a house at the desired
temperature during cold weather indicates that a considerable quantity
of outside air is constantly entering and heated air is leaving the
building. It may be, however, that the ventilation under such condition
is unsatisfactory, even though the amount of air which enters the
building is sufficient in quantity to produce a desirable atmosphere.
If the places of entrance and exit are so located that the entering air
has no opportunity to mix with the air of the building, the advantage
of its presence is lost.

In the burning of fuel in stoves and furnaces, the amount of oxygen
necessary for combustion is supplied by the air which is first taken
into the house and thus forms its atmosphere before it can enter the
heater. Theoretically, about 12 pounds of air are required for the
combustion of a pound of coal, but in practice a much larger amount
actually passes through the heater. As given by Suplee, from 18 to 24
pounds of air are actually used in burning 1 pound of coal. If 20
pounds of air per pound of fuel is taken as an average, there will
be required 198 cubic feet of air per pound of coal consumed. In a
building that requires 10 tons of coal to be used during the winter
months, this would necessitate the average use of 1977 cubic feet of
air per hour, which must be drawn into the house before it can enter
the stoves. This air acts as a means of ventilation and if it is used
to advantage would furnish a supply sufficient in amount to produce
excellent ventilation, considerably more than enough for two people.
The amount of air drawn into the house in this way is further increased
by that which passes into the chimney flue through the check-draft
dampers, when the fires are burning low.

The aim of architects is to construct buildings as completely windproof
as possible, but that such construction is attained in only a slight
degree is sometimes very evident during cold weather. No matter how
tightly constructed buildings may be, most of the contained air filters
through the cracks and crevices of the walls or through the joints
of the windows and door frames, because there is seldom any special
provision made for its entrance. During extremely cold and windy
weather the amount of air that enters the house in this way--because of
the air pressure on the windward side--is sometimes sufficient to keep
the temperature at an uncomfortably low degree. Under such conditions,
the air drifts through the building faster than it can be raised to the
desired temperature and the rooms on the windward side of the building
cannot be kept comfortably warm.

[Illustration: FIG. 162.--A simple expedient for the prevention of
drafts and improving ventilation.]

The common method of ventilation in dwellings is that of partially open
windows. The air thus admitted, being colder and consequently heavier
than that at the temperature of the room, sinks to the lowest level.
In so doing it creates drafts that produce discomfort and act only
in the smallest degree to produce the desired effect of ventilation.
The effect of window ventilation may be greatly improved by a simple
expedient illustrated in Fig. 162. In this, the entering air meets a
deflector in the form of a board or pane of glass that directs the
cold air upward where it mingles with the heated air with the least
production of a noticeable draft. This is the most efficient method of
house ventilating where no special provision is made for the admission
of fresh air.

The object sought in ventilating a room is to keep up the quality of
the air by constant addition of fresh air, and in order to bring about
a uniform purification of the entire atmosphere the entering air must
be mixed with that already in the enclosure. If the discomforts of
drafts are to be avoided, this mixing process must be brought about by
admitting the cold air at the upper part of the room.

[Illustration: FIG. 163.--A chimney flue used as a ventilator.]

Warm air rises to the top of the room because it is lighter than the
colder air beneath it. The coldest air is always lowest in point of
elevation and unless there is some means to stir up the entire volume
this condition will always remain the same.

When the easiest means of air for entering and leaving are near the
floor, the cold entering air and that which goes out will always be in
the lower part of the room, even when the supply is amply large. If no
opportunity is given for the fresh air to mix with that already in the
room, a poor average quality will result.

In the process of ventilation, the entering air should be admitted at,
or directed toward, the highest part of the room, so that the pure
cold air may have a chance to mix with that which is warmest. Air is
not a good conductor of heat, and in mixing warm and cold air the cold
particles will tend to float downward and take up heat from the warmer
air with which it comes into contact, and thus produces a more uniform

[Illustration: FIG. 164.--Method of admitting cold air into rooms so as
to produce the best condition of ventilation.]

The condition most to be desired is that of admitting cold air at a
point where it will most readily mingle with the warm air from the
source of heat. The reduction in temperature that must take place from
this mixture will produce a gravitational circulation. Unfortunately
this is not always possible to attain in an old building, but in the
construction of a new building air ducts placed to admit air at points
near the ceiling and located with reference to the supply of heat will
bring about the best effect of ventilation.

The air which enters a room should, therefore, be near the top or so
directed that the entering shaft will carry it upward. The air which is
taken out of the room should leave from a point near the floor. In so
doing it will tend to produce a more uniform quality and a more even
distributor of the heat.

In order that the most desirable quality of atmosphere may be attained,
there should be a constant supply of pure air entering and an equal
amount discharging from the house. In the better-constructed dwelling
such a condition is often provided through a ventilating flue that is
a part of the chimney. This flue is arranged with registers placed to
take air from the parts of the house requiring the greatest amount of
air. Such an arrangement is shown in the picture in Fig. 163.

Fig. 164 shows the method of Fig. 163 combined with a direct means of
admitting fresh air from the inside. The fresh air ducts should be
provided with dampers to control the effect of extreme cold and wind.

=Quantity of Air Discharged by a Flue.=--Any change of temperature
of air produces a change equal to 1/491 part of its volume, for each
degree variation. If a cubic foot of air is raised in temperature 1°F.,
its volume is 1/491 part larger than the original volume, and its
buoyancy in the surrounding air is increased correspondingly. Air that
has a temperature higher than that surrounding it will tend to rise
because it is lighter. The air rising from a hot-air register or from a
heated surface are illustrations of this condition.

Since the change of volume--or what is the same thing, its tendency
to rise--increases 1/491 for each degree difference in temperature,
the upward velocity of highly heated air will be very great. In warm
air that fills a chimney flue or a room, the same tendency exists, the
warmest air rises to the highest point and if the air can escape, as in
the case of a chimney, a draft will result.

The draft of a chimney, in quiet air, is due to the difference in
temperature between the air inside the flue above that outside the
house. A chimney that does not “draw” and causes a stove to “smoke,”
will often produce sufficient draft after the flue has been warmed. The
upward movement of the warmer air in the flue produces a constantly
increasing velocity, until it reaches the top of the chimney. This is
an accelerated velocity that may be calculated by use of the formula
given in physics, to express the velocity of accelerated motion. The
well-known formula _V_ = √(2_gh_) may be modified to express the
conditions existing in a flue and permit of the calculation of the
quantity of air discharged.

The upward flow of air in a chimney flue being due to the difference
in temperature of the air in the flue over the outside air, the flow
of air from the rooms will continue as long as the difference in
temperature exists. Moreover, the air that is discharged from the
rooms will be replenished from the outside, and for the air sent out
of the flue a corresponding amount will be brought into the rooms
through any openings that exist--door or windows or through cracks
or crevices, depending on the completeness with which the house is
closed. In no case is a house air-tight. The air pressure registered by
the barometer is always the same inside as that outside the building.
During cold weather, when the windows and doors are closed, the air is
escaping through the chimney and also through every little crack and
chink in the top of the rooms where the air is warmest. The colder air
is entering at the same time through the joints about windows, door
casings, through the crevices in the walls and particularly through
the open joints made by the baseboards and the floor. This latter
entrance of cold air is one of the commonest causes of cold floors. The
shrinkage of the baseboards and floors from the quarter-round moulding
which forms the joint leaves openings through which cold air is freely
admitted from partitions and outside walls. The cold, heavier air
remains near the floor because it can rise only when heated or forced
upward by a draft. If the same air were permitted to enter at points
near the ceiling and mingle with the warmest air in the room, a more
uniform temperature would result, as well as better ventilation. The
entering cold air, mixing with the warm air at the top of the room,
would be reduced in its temperature and weight. The heavier air in
falling would diffuse with the air beneath it and thus improve the
general quality of the atmosphere.

It is important to remember that the discharge of air through a chimney
flue will depend, in considerable amount, on the rate the new air is
able to enter the house. In a new, tightly constructed house, the flue
is often capable of discharging air much faster than it can enter, when
it must find its way in through accidental openings. In such cases an
open door or window immediately improves the draft of the stove.

The ventilation in the average dwelling is and must be accomplished
by natural draft that is generated through difference in temperature
of the air. The possibility of providing an acceptable system of
continuous ventilation is confined to the draft of the chimney or to
a flue provided especially for that purpose. Such being the case, the
dimensions of flues constructed for ventilation should be the subject
of investigation. The work that a chimney or ventilating flue has to do
is continuous and will last throughout its lifetime; its proportions
should therefore be considered with more than passing care.

It has been stated that the method of calculating volumes of air that
will pass through a flue is based on the formula used to express the
velocity of accelerated motion. The fundamental formula must be changed
to suit the conditions produced when air is heated and made buoyant by

As has been stated, the change in temperature of air 1°F. causes an
increase or decrease 1/491 part of its volume for each degree change.
Any portion of air, warmer than that which surrounds it, tends to rise
because of its lighter weight; the tendency to rise increases with
the difference in temperature. The draft of a flue is caused by this
condition of difference in temperature between the air inside the flue
and the outside atmosphere.

In order that this general condition may be expressed in the simplest
form let: _T_ = the temperature inside the flue in degrees F.

    _t_ = the temperature outside the flue in degrees F.

    _H_ = the height of the flue in feet.

The quantity (_T_-_t_)/491 expresses the difference in temperature in
degrees, divided by the change of volume for each degree. This gives
the constant upward tendency of the air in passing through the flue. If
this quantity is placed in the formula _V_ = √(2_gh_), so as to
exert its influence through the height of flue _H_, the condition may
be expressed:

    _V_ = √(2_g_((_T_-_t_)/491)_H_)

The factor _g_, representing the acceleration of gravity, is constant
and equal to 32 feet per second. The quantity 2_g_ may be removed from
under the radical and the formula becomes:

    _V_ = 8√(((_T_-_t_)/491)_H_)

The formula may now be used to express the volume of discharge of air
from a flue. Suppose such a flue contains an area of 1 square foot in
cross-section and that it is desired to estimate the air discharged
from the flue per hour. The value of _g_ is given in feet per second,
and in order to make the formula express the volume of air discharged
in cubic feet per hour, it must be multiplied by the number of seconds
in an hour. Volume discharged in cubic feet per hour

    = 60 × 60 × 8√(((_T_-_t_)/491)_H_)
    = 28,800√(((_T_-_t_)/491)_H_)

This formula applies to conditions such as will permit uniform movement
of the air in a straight flue, uninfluenced by irregular, odd-shaped
passages and rough surfaces. Moreover, it is supposed that the air may
enter the house as rapidly as it escapes. The theoretical discharge
will, in most instances, be less than the calculated amount, because
the air cannot enter the house as fast as it may be discharged by the
flue. It is a common custom to consider the theoretical flue only 50
per cent. efficient. As applied to the formula, the constant 28,800
when reduced 50 per cent. will become 14,400, and will be so used in
the calculations as follows.

As an illustration of the application of the formula, suppose that the
temperature in the house and in the flue is 70°F. and that the outside
temperature is 20°F. The height of the chimney is 30 feet. The area of
the flue is 1 square foot.

    Volume = 14,400 √(((_T_ - _t_)/491)_H_)
           = 14,400√(((70 - 20)/491) × 30)
           = 25,140 cubic feet per hour.

Such a ventilating flue would be sufficient in size, under the
conditions given, to furnish air at the rate of 25,140 cubic feet per
hour or 30 cubic feet per minute to 13 persons, provided of course
that the air could enter the building at the rate demanded. Where no
provision is made for the air to enter the building it must find its
way by the accidental openings. A common illustration of this effect
may be noticed in the rate at which the fire of a stove will burn
in a tightly closed room. The opening of a door or window causes an
immediate increase of combustion, because of the extra air supply.
It is evident that in well-constructed houses other means should be
provided for admitting air than that of accidental opening.

The following table calculated by the above formula gives the quantity
of air in cubic feet per hour discharged through a flue of 1 square
foot cross-section. The table shows the calculated discharge from flues
of heights varying from 15 to 40 feet, and with temperature differences
from 10° to 100° between the outside air and that of the house.

  Height  | Temperature of air in the flue above that of external air
  of flue +--------+--------+--------+--------+--------+--------+-------
  in feet |   10   |   15   |   20   |   25   |   30   |   50   |  100
     15   |  7,980 |  9,720 | 11,280 | 12,550 | 13,800 | 17,820 | 25,140
     20   |  9,180 | 11,180 | 13,080 | 14,520 | 15,900 | 20,520 | 29,040
     25   | 10,260 | 12,600 | 14,520 | 16,260 | 17,820 | 22,980 | 32,460
     30   | 11,280 | 13,800 | 15,900 | 17,825 | 19,500 | 25,140 | 35,580
     35   | 12,180 | 14,880 | 17,160 | 19,200 | 21,060 | 27,180 | 38,400
     40   | 13,020 | 15,900 | 18,360 | 20,520 | 22,500 | 29,040 | 40,980

In Fig. 163 is illustrated the form of chimney that is often used for
the ventilation of dwellings. This is built with three flues. The flue
to the left--marked _A_ at the top--is intended to carry away the smoke
and gases from the kitchen range. The flue to the right is that to
which is connected the smoke pipe from the furnace. The flue in the
middle marked _B_ is for ventilation. Occupying as it does the space
between the other two, it is kept warm by the heat of the other flues
and the draft is thus increased. Openings to the flue are shown in the
different floors at the points _R_ and _S_. The openings are furnished
with registers which may be regulated to suit the weather conditions.

The dimensions of such a flue may be calculated by the formula given
or the area may be taken from the table to correspond with required
conditions. In all cases flues should be made ample in size, as they
must often do their maximum work under the poorest conditions for the
production of good draft.

The amount of air discharged from the flue as given in the table is
due to the gravitational effect alone. The suction produced by the
wind adds in a very large degree to the amount of air discharged. The
quantity of air that will flow from a 30-foot flue, by reason of the
suction of the wind, blowing 7 miles per hour is equal to the same flue
working by gravity with a temperature difference of 20°. With a wind
velocity of 7 miles per hour and a temperature as given, the capacity
of the flue is doubled. It is easy, therefore, to understand why the
rate at which fires burn is so greatly increased by high winds. At the
time of very high winds, a chimney flue will carry away three and even
four times the volume discharged at the time of atmospheric calm.

=Cost of Ventilation.=--The cost of good ventilation is often looked
upon as prohibitive, because of the expense in heat necessary to keep
the inside atmosphere at standard purity. Cost of ventilation is
determined by analysis of the known conditions and calculations made of
the amount of extra heat necessary to warm the greater volume of air.

The common practice of estimating the quantity of heat used in any
form of heating or ventilation is by reference to the B.t.u. used in
producing the desired condition. This unit, as has already been stated,
is the amount of heat necessary to change a pound of water, 1°F.

In considering the cost of heating the air for ventilation, it must be
borne in mind that the heat used in raising the temperature of the air
contained in an enclosure is only a part of that necessary for warming
the building. Most of the heat used goes to keep up the loss due to
radiation and conduction which goes on from the windows, the walls and
other parts of the building that are exposed to the outside cold. The
material of which the building is composed must be heated and in turn
radiates its heat to the colder outside air.

The quantity of heat necessary to change the temperature of a
definite amount of air is easy of calculation. The problem is that of
determining the number of heat units required to warm the necessary air
to suit the average condition of weather. We will assume that the house
is heated to the normal temperature 70°, and that the additional cost
of heating the air for ventilation over the amount thus expended is the
cost of ventilation.

Assuming that the house is so constructed that it is possible to supply
air at the rate of 1000 cubic feet per hour to each person of a family
of five, this condition will necessitate 5000 cubic feet of air per
hour or 120,000 cubic feet of air per day.

The house is such that 10 tons of coal are required per year, at a
cost of $10 per ton. The period of winter weather will be considered 5
months of 30 days each. This will be 150 days, during which the fuel
for heating the house will cost 66-2/3 cents per day.

The average temperature of the outdoor air during the entire period
will be assumed to be 20°F., thus requiring the air for ventilation to
be changed 50° in order to raise it to the normal temperature, 70°.

The weight of a cubic foot of air at 70° is practically 0.075 pound.
The 120,000 cubic feet of air used per day will, therefore, weigh 0.075
× 120,000 = 9000 pounds which must be raised 50° in temperature.

In order to express in B.t.u. the necessary heat required to produce
the change of air temperature, the quantity of air is best stated in an
equivalent amount of water. The specific heat of air is 0.237; that is,
the amount of heat necessary to change a pound of air 1° is 0.237 of
the amount used in changing 1 pound of water 1°. The 9000 pounds of air
expressed as an equivalent amount of water will then be:

    9000 × 0.237 = 2133 pounds of water.

This amount of water raised 1° is equivalent to raising 120,000 cubic
feet of air 1°. Now the average change in the temperature of the air is
50°, so that 50 × 2133 will be the number of heat units used.

    50 × 2133 = 106,650 B.t.u.

That is, 106,650 B.t.u. will be required to heat the air for
ventilation one day.

In order to express this amount of heat in terms of fuel consumed, it
will be assumed that the coal contained 14,000 B.t.u. per pound, this
being a fair valuation of good coal. The average house-heating furnace
will turn into available heat about 50 per cent. of the fuel burned.
This value is taken from house-heating fuel tests made at the Iowa
State College. The available heat in each pound of coal then will be
7000 B.t.u.

    106,650 ÷ 7000 = 15.2 pounds of coal.

That is, 15.2 pounds of coal per day must be burned in order to furnish
1000 cubic feet of air per person each hour at the desired temperature.

At $10 a ton of 2000 pounds, the fuel costs 1/2 cent per pound. The
cost of ventilation is, therefore, 1/2 × 15.2 = 7.60 cents a day, not
an extravagant amount for good air.

It is evident that with the use of hot-air furnaces which take their
entire amount of air from outdoors, the extra amount of heat necessary
for this improved quality of atmosphere is very well expended. The use
of ventilating devices adds only a relatively small amount to the total
cost of heating and provides for the well-being of the occupants of the
house--in the form of good air--an amount of healthfulness impossible
of calculation.

The best ventilation is attained where a constant supply of fresh air
is admitted to the house at points from which the best circulation may
be secured and equal quantities of vitiated air are removed from the
different apartments.

It is understood that in the process of natural ventilation the desired
condition can only be approximated and that the permissible ventilation
appliances are so placed as to give results such as to permit the air
to follow the natural laws that must prevail.

If the house is heated by stoves, the outside air is best admitted near
the ceiling, so that the cold air on entering may come into contact and
mingle with the warmest air in the room. The circulation will by this
method be effected by gravity.

In the use of the hot-air furnace, the air supply--as has already
been explained in the figures on pages 55 and 58--is brought from the
outside, where after being heated it enters the rooms through the
registers placed near the floor. Being warmer than the air in the room,
it tends to quickly rise. The currents set up by its motion help to
produce a uniform temperature and to diffuse the new air through the
entire space. The more evenly the air is distributed the more uniform
will be the condition of temperature of the room.

In hot-water and steam heating, the direct method of heating in Fig.
29 and the indirect method of Fig. 30 show two forms of apparatus
for admitting air to buildings that are quite generally employed
for ventilation of dwellings. In the use of all such devices for
ventilation purposes, there should be provided means of escape of air
corresponding in amount to the fresh air admitted. The exhaust air vent
should be located near the floor to bring about the best results. The
degree of success attending the use of such apparatus will depend on
the amount of care taken, to suit the position of the dampers to the
prevailing weather.

[Illustration: FIG. 165.--The Wolpert air tester; an instrument used to
determine the quality of air.]

=The Wolpert Air Tester.=--The purity of air is expressed by quantity
of carbonic acid gas included in its composition. In order to determine
the degree of purity of any atmosphere the amount of contained gas must
be determined. This is accomplished by use of simple apparatus that may
be successfully operated by those who are unacquainted with chemical
analytical methods. The process is due to chemical action but the
manipulation of the required apparatus is purely mechanical.

Fig. 165 shows the Wolpert air tester which is a form of this
apparatus that has given general satisfaction. The results attained
by its use are approximate but sufficiently exact for all practical
purposes. The apparatus consists of a graduated glass tube in which
fits a rubber piston mounted on a hollow glass rod, through which the
sample of air is admitted to the tube. The chemicals used for absorbing
the carbonic acid gas are furnished with the instrument but may be
replenished without difficulty. Directions for its use are furnished
with the tester that may be readily followed after a trial. The results
obtained are read directly from the side of the tube. The tester may be
obtained from any dealer in chemical or physical apparatus.

[Illustration: FIG. 166.--Thermostat regulator and motor-valve attached
to a radiator.]

=Pneumatic Temperature Regulation.=--Pneumatic temperature regulation
is very generally used in large and complicated heating systems,
because of its positive action and completeness of heat control. This
method of heat regulation utilizes the energy of compressed air, with
which to open and close the valves of the radiators. It may be adapted
to any mode of heating and can be used with any size of plant, but is
particularly suited to extended systems. The radiators, providing heat
for any particular space, are under control of separate thermostats,
which by means of motor valves admit heat only as required. A motor,
operated by compressed air, is attached directly to each radiator
valve. Any change in temperature of the room causes the thermostat to
correct in the radiator the required amount of heat.

With this method of regulation the temperature-controlling element
of the thermostat, like that of the electro-thermostatic system, is
a sensitive part, which by expanding and contracting with the heat
and cold directly controls the heat in any part of the building. The
motive power for opening and closing the valves of steam or hot-water
radiators or for operating the dampers in a hot-air system is supplied
by compressed air. The air supply is furnished by an air compressor
which automatically stores air under pressure in a pressure tank, from
which is drawn the necessary energy, as occasion demands. The air is
conducted to the motors through small pipes which are connected with
the regulating elements and also with the motors. The function of the
thermostat is to so govern the air which enters the motor as to correct
any change in the temperature of the rooms. This it does by opening and
closing the valves as occasion demands.

In Fig. 166 is shown the arrangement of the thermostat _T_ as it
appears on the wall. Air from the supply tank is conveyed by the pipe
_A_ through the thermostat _T_ to the motor valve _V_ attached to the
radiator. The function of the thermostat is that of so controlling the
radiator valve by means of the motor _V_ that the radiator will give
out just sufficient heat to keep the room at the desired temperature. A
closer view of the thermostat is given in Fig. 167.

[Illustration: FIG. 167.--Outside view of thermostat as it appears in

The thermostat illustrated in Fig. 167 is that employed by the National
Regulator Co. The drawing shows the exterior and interior construction
of the parts enclosed in the previous illustration. The pipe _C_ at
the right and opening _P_ at the left are the same as _A_ in Fig. 169;
likewise, the pipe _D_ connects at the opening _M_ of the motor valve
in Fig. 169.

Referring again to Fig. 168, the sensitive part consists of a tube
_A_ of vulcanized rubber. It is the dark-shaded part in the left-hand
drawing. Any change in the air temperature influences the length of
this tube. The changing length of the tube effects the air supply to
close the radiator valve when the temperature rises above the desired
amount and to reopen it when more heat is required. A finely threaded
screw passes through the plug _H_ at the top and to this is secured the
indicating disc _X_. The bottom of this screw is cupped to receive the
point of the rod _K_, which connects with the piece _L_. Any change in
length of the sensitive tube moves the valve lever _O_, and thus opens
or closes the air port _G_.

Air under pressure is supplied by the pipe _C_, connected to the
air supply, flowing into the thermostat through the filter _P_, the
restriction _S_, the passage _T_, and the port _G_. The adjustment of
the thermostat for different temperatures is provided for by the screw
_J_ through the top plug _H_, and the indicating disc _X_. The screw
_R_ in the connector _Q_ at the base of the thermostat is a needle
valve which opens or closes the connection with the air supply, and
is used as an air shut-off valve when it is desired to remove the
thermostat. The screw _S_ is a restriction valve which controls the
supply of air to the thermostat, and this screw is set so as to allow
the air to pass in a restricted quantity.

[Illustration: FIG. 168.--Internal construction of the National
Regulator Co.’s thermostatic regulator.]

When the temperature of the apartment has risen so as to expand the
thermostatic element _A_, the pressure on _K_ and _L_ is relieved
and the spring _N_ closes the port _G_. The air admitted through the
restriction screw _S_, since it cannot escape through the port _G_,
accumulates in the passage _Y_ and pipe _D_, filling the diaphragm and
moving the valve into the position to decrease the supply of heat.
When the temperature of the apartment has decreased so as to produce
pressure on the connecting rod _K_, through the contraction of the
thermostatic element _A_, the port _G_ will be opened by the valve
lever _O_, allowing the air in the pipe _D_, together with that which
flows through the restriction _S_, to escape through the passage _W_
to the atmosphere, allowing no air to accumulate in the pipe _D_, and
thus permitting the spring at the diaphragm to actuate the damper or
valve for more heat. The amount of air released through the port _G_ by
the valve lever _O_ varies the pressure accumulated in the pipe _D_ and
produces the graduated or intermediate action desired.

[Illustration: FIG. 169.--Cross-section of pneumatic radiator valve
showing its internal construction.]

[Illustration: FIG. 170.--Pneumatic motor valve for automatic control
of dampers, etc.]

A further application of air pressure in temperature regulation is
that of the type of motor shown in Fig. 170. This device is intended
to open and close dampers such as are used in the automatic regulation
of temperature where heated air is used to warm the buildings. The
operation of the motor is the same as that which controls the steam
valve. The pressure exerted by the diaphragm is applied at _A_ and the
attachment to the damper is made at _B_. The motors indicated at _V_
and _N_ in Fig. 174 and _D_ in Fig. 175 are examples of its application.

=Mechanical Ventilation.=--Draft ventilation produced by open windows,
flues and chimneys is influenced by extremes of temperature and by
the force and changing direction of the wind; it is, therefore, but
imperfectly controlled. The superiority of mechanical ventilation
is generally recognized because the amount of entering air may be
regulated to suit any circumstance and its temperature and humidity
varied to conform to any desired atmospheric conditions. Mechanical
ventilating plants are seldom employed in any but the more pretentious
dwellings, but their use has extended to a degree that they are
occasionally installed in apartment buildings and their further
application is likely to grow. Neither the cost of installation nor the
expense of operation is prohibitive in dwellings of the better types.
Mechanical ventilation is quite generally employed in school buildings,
auditoriums, hospitals, public buildings and others where means will
permit, and there is a universal recognition of the effects of the
agreeably conditioned air.

Mechanical ventilation may be accomplished by power-driven fans, either
by exhausting the air from the building or by forcing air into it, and
under some conditions a combination of the two methods is used.

[Illustration: FIG. 171.--Exhaust fan for induced ventilation.]

[Illustration: FIG. 172.--Ventilation apparatus in which is included
the heater coils, the fan and the motor.]

The exhaust method of ventilation is that in which air is blown out of
the building by a fan; and the supply, to replenish that taken away,
is conducted into the building through ducts prepared for the purpose.
In some cases the induced air supply leaks into the rooms through the
joints in the doors and windows, and through the accidental crevices.
In Fig. 171 is shown a simple exhaust fan installed to produce such a
change of air. It is suitable for kitchens and other places where it
is desired to eliminate smoke or gases rather than to produce a supply
of air. With this apparatus the air of the room is blown out by the
rotating fan and new air to take the place of that exhausted is drawn
in at any convenient opening.

=The Plenum Method.=--That form of mechanical ventilation by means of
which air is forced into the rooms is known as the plenum method. It is
the most positive means of air supply because its action is attended by
a slight pressure above the outside air; it is continuous in action and
the amount of entering air is under control. The escape of the expelled
air is made through vent flues especially constructed for the purpose.

=Ventilation Apparatus.=--Fig. 172 illustrates the form of apparatus
used for ventilating buildings where no attempt is made at washing or
humidifying the air. Enclosed in a sheet-iron case _C_ is a fan which
is driven by the electric motor _M_. The capacity of the fan, for the
delivery of air, is made to suit the requirements of the building. In
this case the fan is secured to an extension of the armature shaft of
the motor. Connecting with the case which encloses the fan is another
sheet-iron box _H_, containg coils of heating pipe. The heating
apparatus is designed to change the temperature of the entering air to
suit the requirements of the building.

This represents the draw-through or induced-draft type of ventilation
apparatus. The air delivered by the fan induces a flow of outside air
which is drawn through the heating coils and discharged through the
opening _E_. At this point it enters the main ventilation duct from
which it is distributed by branch conduits throughout the building.

The temperature of the air sent out from the fan is regulated by the
steam valves of the heater coils to suit the prevailing conditions.
Under some installations of this character the ventilating air is
made to furnish the heat necessary to warm the building as well as to
provide its air supply. As ordinarily used, however, the temperature of
the ventilating air is the same as that of the room.

The method of conveying air to the various apartments depends entirely
on local conditions. The conduits may be made of sheet iron, placed to
suit the existing conditions; but when a building is constructed with
a ventilating plant in view as a part of the building equipment, it is
customary to make the ducts part of the partitions. In brick buildings
the ducts are constructed, so far as it is practicable, in the walls.
These ducts are made in size and arrangement to suit the amount of
air required for each room. When the plant is put into operation each
duct is tested with an anemometer which indicates the velocity of the
entering air. The calculated amount of air, determined by the velocity
and area of the entering column, when compared with the necessary
quantity demanded for good ventilation, gives the efficiency of the

=Air Conditioning.=--In addition to the possibility of a constant
supply of air, a combination of the exhaust and plenum methods admits
of air purification. With such a plant, the air may be washed free
from all suspended dust or gases and moistened to any degree of
humidity. The process of washing and humidifying air is known as air
conditioning. Apparatus for air conditioning is made in a variety
of forms to produce any desired extent of air purification and any
degree of humidity. The plant may be regulated by hand or it may be
made entirely automatic in its action. Air-conditioning plants may be
arranged to produce air that is purified, humidified and warmed during
winter weather and in summer the hot humid atmosphere may be cooled and
dehumidified to a temperature and percentage of moisture that is most

Conditioned air is often used in manufactories, not for the purpose of
supplying good air to the employees but because of the effect of the
atmospheric air on the products. The manufacture of textile fabrics
often demands a constant atmospheric humidity in order that the
material produced may be uniform in grade; this is particularly true in
the making of silks. Various manufactories require an atmosphere free
from lint and dust in order that the best quality of material may be
produced. The air for ventilation in such places is washed free from
all suspended matter before being sent into the building.

In Fig. 173 is indicated an application of apparatus similar in
construction to that just described. The arrangement of the parts
is such as to produce a Plenum hot-air system of ventilation and
temperature regulation.

The plant occupies a room in the basement and the drawing shows the
method of heating, together with the plan of distribution. The air
duct leading to the room above furnishes an example of the manner of
admitting the warmed air to the rooms. The dampers _C₁_, _C₂_, etc.,
are controlled by separate motors. The motor _M_ is under the control
of the thermostat _T_ in the room above. Any change of temperature in
the room is corrected by the damper to admit cold or warm air as is

[Illustration: FIG. 173.--Plenum hot-blast heating system with
temperature regulation.]

The power-driven fan _F_ draws in outdoor air from an opening _A_,
through a set of heater coils _H₁_, in which it is raised considerably
in temperature. The heater in this case is a coil of steam pipes. The
air--after being warmed--is taken into the fan and from it may be sent
through a second set of coils _H₂_, to receive additional heat, or if
already sufficiently warmed the air from the fan may pass under the
second set of coils and receive no heat from them. Under the first
heater coil is also a bypass which may be opened by the motor _N_ to
admit cold air that is drawn directly into the fan. The movement of
the air through these bypasses is under control of the thermostat,
which causes the motor _N_ to open or close the bypass to suit the
temperature of the room. When the bypass is opened the steam is shut
off from the heater coils.

Examination of the drawing will show that the air from the fan may pass
through a second heater _H₂_, to the place marked _warm air_, or it may
pass under the heater to the compartment marked _cold air_. The amount
of warm and cold air which enters the duct is regulated by the position
of the dampers _C_.

The position of the dampers _C_, which is controlled by the motors _M_,
is made to take amounts of cold or warm air to produce the desired
temperature in the rooms. The motors _C₁_, etc., are under control of
the thermostat in each room. Any change of temperature in the room will
immediately affect the thermostat. The effect on the thermostat will
so change the air pressure in the motor that the valve _C_ is moved to
correct the difference in room temperature. If warm air is demanded,
the motor changes the damper _C_ to close the cold-air supply and take
air that must pass through the heater coils _H₂_. If only cold air is
desired the damper will turn to shut off the course through the heaters
and admit air directly from outdoors.

=Humidifying Plants.=--Mechanical ventilation plants that are intended
for washing the air may be made up of parts similar to that of Fig.
173, but in addition to the apparatus shown provision is made for the
air to pass through a chamber filled with a spray of water. The air in
passing through this spray is washed free of dust and at the same time
absorbs water necessary for its desired humidity.

The humidity of air may be increased by the addition of moisture or
decreased (dehumidified) by raising its temperature, thereby increasing
its capacity for containing moisture. Suppose that air at 50° is
saturated with moisture; it will contain practically 4 grains of water
per cubic foot. If now the temperature of the air is raised to 70°, the
same amount of air is capable of containing 8 grains of water and is,
therefore, only 50 per cent. saturated.

Humidification is accomplished in air-conditioning plants through
one of two general methods: by the evaporation type of apparatus, in
which the passing air absorbs moisture from contact with a large area
of water; or the spray method, in which the water is broken into a
very fine spray by a specially devised nozzle and thus rendered easy
of absorption by the air to be moistened. A third method is sometimes
employed, in which steam is introduced into the air supply. Steam is
already vaporized water and immediately becomes a part of the air
without further change. The steam type of humidifying plant possesses
features that limit its application, in that the steam in some cases
may possess objectionable odor or includes the vapor of grease,
either of which would materially effect its use. Further, the heat
of vaporization liberated by the condensing steam is also a factor
that influences the temperature of the air and in case of direct
humidification must receive special attention.

=Vaporization as a Cooling Agent.=--The evaporation of water has a
distinct value aside from humidifying the air, in that the cooling
effect is in direct proportion to the added moisture. In the process of
evaporation the heat necessary to change the water into vapor is taken
from the surrounding air and the temperature is thus materially lowered.

In practical air-conditioning apparatus, of the evaporative or spray
types, the process consists of drawing the outside air into a chamber
filled with falling water that is broken up into drops like rain or
spray. In passing, every particle of the air comes into contact with
the water drops; the almost invisible particles of dust adhere to the
water and are carried away leaving the air washed clean. In addition
to freeing the air from dust, the intimate mixture of the air permits
of a ready absorption of the water, which is taken up to any per cent.
of saturation. After leaving the spray chamber, the moisture-laden
air passes through an eliminator in which any unabsorbed moisture
is extracted. It is possible for air to become not only completely
saturated with water under the conditions encountered in a humidifying
plant, but in addition, the movement of the air may carry along
unabsorbed particles that are precipitated directly after leaving the
spray chamber. For this reason the air is passed through an eliminator.

The eliminator is composed of a series of irregular sheet-metal
surfaces so arranged that the air is required to abruptly change its
direction several times in its passage of a short distance. The impact
of the air against the surfaces and the centrifugal force exerted by
the sudden changes of direction throw out the excess moisture and any
remaining suspended matter the air may contain.

The saturated air from the eliminator passes through a heater where the
temperature is raised to that of the rooms. In the rise of temperature
the air which is saturated is rendered capable of absorbing more
moisture, and hence has been dehumidified. The rise of temperature and
the corresponding decrease in relative humidity is intended to be such
as to leave in the finished air the desired percentage of moisture.

=Air-cooling Plants.=--The use of air-washing and humidifying plants
so far mentioned has been confined to elimination of dust and the
addition of moisture to air, under winter conditions. The same type of
apparatus, used in summer, becomes a cooling plant, and by observance
of the necessary requirements may be used to produce agreeable
atmospheric conditions during hot weather.

When used for such purpose the air is washed, by passing it through
falling water which frees it from dust and reduces its temperature.
It is then further cooled by passing over cold surfaces that take the
place of the heaters used in cold weather. The cooling surfaces are
pipe coils kept cold by the contained water which comes from the water
supply or from a refrigerating plant. The temperature and humidity are
thus changed to suit the requirements of the conditioned air.

During the hot weather of summer the most disagreeable atmospheric
condition is that caused by humidity near saturation, at a time of
relatively high temperature. Under such conditions the cooling plant
not only cools the air, but causes a precipitation of the moisture on
the cold surfaces which are kept below the dew-point. The air is cooled
and dehumidified to a point such that the conditioned air produces an
agreeable atmosphere. The regulation of the degree to which the air
is cooled is accomplished by the same general methods as are used in

=Humidity Control.=--The method of regulating atmospheric humidity in
a humidifying plant will be determined by the conditions under which
it is intended to work. There are a variety of means employed that may
be used to bring about the same effects, each of which is particularly
suited to certain requirements. The present object is to describe the
essential features of airconditioning plants, by use of illustrations
representing each of the three methods mentioned above. That of the
ventilation of a school building under winter conditions will be taken
as an example.

In Fig. 174 is shown a heating and ventilating system in which the
air conditioning is accomplished by automatic regulators for both
temperature and humidity. The plant occupies a room in the basement,
and a room directly above illustrates the conditions that prevail in
all of the other rooms of the building. The principal features of the
plant are the fan _G_, which supplies the air; the hot-air furnace _H_,
which furnishes the heat; and the water spray _S_, which provides the
moisture with which the air is humidified.

[Illustration: FIG. 174.--Furnace blast system of heating, with
temperature regulation and humidity control.]

The air is drawn in at _A_ to a room in which a motor-driven fan _G_
forces the supply through the heating apparatus into the building. The
air after leaving the fan passes through a cold-air duct _C_ to the
heating surfaces _H_ to be warmed. The air in passing over the heating
surfaces is raised to a degree considerably above the temperature of
the rooms. The hot air leaving the heater _H_ enters the tempered air
chamber _T_ through the passage _K_. A damper _M_ provides means for
also admitting cold air to the chamber _T_ directly from the fan. The
thermostat, located at _O_, is connected with a pneumatic motor _V_
(similar to Fig. 170) which regulates the supply of cold and hot air
from _K_ and _M_ to suit the desired temperature of the air supply
for the rooms above. The arm of the motor _V_ is so arranged that an
upward movement opens the cold-air and closes the hot-air passages;
the downward movement produces the opposite effect. The motor _V_ thus
controls the temperature of the air.

In this system the air is humidified by a direct water spray marked
_S_ in the drawing. A part of the hot air from the heater _H_ may
escape through the damper _W_ and absorb water on its way to the duct
_D_, which takes the air to the room above, where it enters through the
register _E_. This air as it comes from the heater, being hot, will
absorb a larger amount of water than the air could hold when cooled
to room temperature; for this reason only a part of the air supply is
humidified. The supply of the hot humid air is admitted to the duct _D_
in such quantity as will produce the desired degree of humidity in the

The degree of room temperature is governed by the thermostat, in the
room, which, by means of the motor _N_, controls the damper _F_. This
damper admits hot humid air and the tempered air from the chamber _T_
in proper proportion. At any time the humidity of the air in the room
reaches the maximum amount for which it is set, the humidostat, through
its motor, closes the valve _R_, which controls the water supply to the
spray nozzle, and the moisture in the air is reduced until a further
amount is demanded. With apparatus of this kind the temperature and
humidity may be kept practically constant.

[Illustration: FIG. 175.--Direct steam heating system with mechanical
fan-blast ventilation, temperature regulation and humidity control.]

Fig. 175 shows another arrangement of a similarly controlled plant in
which steam is used for humidifying the air. The air is admitted at
_A_, from whence it passes through a steam-heating coil _S_, which
raises it to a predetermined temperature. The steam jets are arranged
at _H_, for providing the necessary moisture. The humidostat through a
motor valve _V_ governs the amount of steam that is permitted to enter
the humidifying chamber. A thermostat located in the air duct at _B_
controls the temperature of the air sent to the rooms by regulating the
amount of heat given out by the steam coils _S_. This control is made
still more sensitive by use of a cold-air bypass. The damper _D_ is
opened by a motor valve to admit cold air at the same time the steam is
shut off from the heater coils.

In this plant the ventilating air is not intended to supply all
of the heat to the rooms. A thermostat on the wall controls the
room temperature by regulating the amount of steam admitted to the
radiators. In the ventilating plant previously described, all of the
heat for the building is supplied through the ventilating system; in
the plant shown in Fig. 175, the heating apparatus which warms the
building is entirely separate and may be used when the ventilating
system is inoperative.

The humidity is controlled by admitting saturated air to the warmer air
of the rooms in such quantity as will produce the desired mixture. The
humidostat, on the left-hand wall, regulates the quantity of moisture
by opening or closing the steam valve _V_ as occasion requires.

Another example of air-conditioning plant similar in principle to that
just described is often called the dew-point system. It depends for
its action on a definite dew-point temperature at which the air is
saturated with moisture, before being heated to room temperature. The
air to be conditioned is first warmed, by passing through a set of
tempering coils, to a degree at which it will contain the necessary
moisture when saturated. After saturation the temperature is raised by
a second set of heating coils to the room temperature, the moisture
contained being right to give the desired humidity.

To illustrate, suppose that it is desired to maintain a constant
humidity of 50 per cent. saturation at 70°F. in the building. The
temperature at which the air must be saturated, to contain 4 grains of
moisture per cubic foot, is found in the table on page 199 to be 48°F.

The entering air must first be raised to that temperature by the
tempering coils. The air then enters the spray chamber where it absorbs
moisture to saturation, by contact with a multitude of water particles.
This saturated air now passes through a second set of heated coils and
takes up heat sufficient to raise it to the finished temperature.

The dew-point temperature at which the air enters the spray chamber
and the final temperature are kept constant by motor-operated valves
which supply the heating coils with the necessary heat in the form of
steam. The motors are controlled by thermostats, placed to measure the
temperature of the air as it enters the saturator and the finished air
as it enters the rooms. If these conditions are now kept constant, the
finished air will be constantly 50 per cent. saturated.

[Illustration: FIG. 176.--School building section showing a complete
air-conditioning plant.]

A plant of this character is illustrated in Fig. 176. The figure
shows the exterior of the casings which enclose the tempering coils
and saturator at _A_, the eliminator at _B_, and the heating coils at
_C_. This is another draw-through type of plant where a fan, enclosed
in _D_, draws the air through the conditioning apparatus and forces
it through the sheet-iron ducts _E_. The passages in the walls--as
indicated by the arrows--conduct the air through the register _R_, into
the room. The register _S_ represents the discharge duct through which
the vitiated air is forced from the room.

In this system of air conditioning, all of the ventilating air is to
be saturated with moisture at a temperature such that when raised to
room temperature will contain the desired percentage of humidity. The
saturator occupies the space between _A_ and _B_. A number of spray
jets are arranged to fill the entire space with water drops that are
moving in every direction. The air, as it passes, must come into
contact with the drops again and again, until by repeated impact each
particle is completely saturated and at the same time washed free from
dust. It has already been explained that the movement of the saturated
air through a mass of spray will carry with it a considerable amount
of unabsorbed water that must be taken out by an eliminator. A section
of the casing is broken out at _B_, showing the eliminator plates. The
irregular surfaces of these plates repeatedly change the direction of
the passing air, and the suspended water or remaining solid matter is
thrown against the surfaces where they adhere. The moisture accumulates
in drops of water that run down the plates to the bottom of the
enclosure and finally into the sewer.

From the eliminator the air passes through the heating coils enclosed
in _C_, where it is heated to the necessary temperature for admission
to the rooms.

The regulation of the temperature of the tempering coils and heating
coils is accomplished as in the other plants described. The thermostats
with their motors operate the valves of the heaters to admit steam
sufficient to keep constant temperatures at the different parts. The
humidity is maintained at a constant amount by saturating the air at a
constant temperature and therefore no humidostat is required.



=Gaseous and Liquid Fuels.=--Gaseous and liquid fuels used for
domestic illumination and heating may be divided into three general
classes--coal gas, including carburetted water gas and producer gas
and their various mixtures; oil gas, acetylene and gasoline gas. Of
these the first is the most important as an illuminating gas, while for
industrial and domestic purposes producer gas is of no importance as a
fuel gas. Gasoline, acetylene and oil gases are generated and used to a
remarkable extent in isolated dwellings as fuel and for illumination.

The value of any gas for domestic purposes will depend on the amount
of heat that is produced when it is burned. In the earlier days of its
use coal gas was employed entirely as an illuminant and its value was
expressed in illuminating power; at the present time the standard often
prescribed by regulation is that of its illuminating capability and is
stated in candlepower. There is, however, a tendency to establish the
more consistent standard of expressing the value of gas by its heat
value. The reasons for this is the general use of mantle gas burners
which depend on the heating value alone for their efficiency and the
fact that coal gas is very extensively used for domestic fuel.

=Coal Gas.=--Coal gas is derived from the solid hydrocarbons of coal
transformed into the more convenient, gaseous form of fuel by means of
distillation. Coal gas was first made by distilling coal from an iron
pot over a fire and to some extent this is still the principle of the
present practice. The gas as it comes from the retort is subjected to
a refining process of washing and scrubbing to remove the undesirable
properties when it is stored in a large gasometer for distribution
through pipes to its places of use. Coal gas is now used largely for
fuel as well as for lighting. Unless the heating value of gas is
regulated by law in any community and determinations of its quality
are made regularly by some competent official, the amount of heat
contained in coal gas is entirely at the option of the manufacturer and
manager’s conscience. The value as given in the table on page 252 is
the number of B.t.u. coal gas should contain. The heating value of any
gas is determined by burning the gas in a calorimeter made expressly
for the measurement of the heat of combustion for each foot of the gas

=All-oil Water Gas.=--In places where an abundant supply of cheap oil
is available, all-oil water gas has met with a great deal of favor. It
is made by atomizing crude oil by a blast of steam in a heated chamber
where a combination of the vaporized oil and steam form a gas. In
general the gas resembles coal gas and as given in the table on page
252 is slightly higher in heating value.

=Pintsch Gas.=--One of the commercial adaptations of oil gas is that of
the Pintsch process of compressing the gas in tanks for transportation.
In the Pintsch process, the gas is subjected to a pressure of 10
atmospheres--about 150 pounds. This condensation permits a sufficiently
large volume of gas to be stored in tanks as to make possible the
lighting of railroad trains, etc., by gaslight. The pressure of the gas
is reduced by an automatic regulating valve to that required by the
burner. The flame is very much the same as that produced by coal gas.

=Blau Gas.=--Another commercial adaptation of oil gas is that known
as Blau gas. In this process of storage the gas is subjected to 100
atmospheres of pressure--about 1500 pounds. This pressure is sufficient
to liquefy the gas and as a result a large amount can be transported
in a relatively small space. According to Fulweiler 1 gallon of the
liquefied gas will yield about 28 cubic feet of the expanded gas and
there will remain a residue that may run up to 9 per cent.

=Water Gas.=--When the vapor of water is brought into contact with
incandescent carbon, the water is decomposed and sufficient carbon
is absorbed to produce a fuel gas. Its manufacture depends on the
decomposition that takes place when steam is blown into a bed of
incandescent coal. The gas made by this reaction is a water gas, but
due to the fact that when burned it gives a blue flame, it is known
as “blue gas.” It has a heating value of about 300 B.t.u. per cubic
foot, and as compared with coal gas which gives 622 B.t.u. per cubic
foot, would be reckoned at about one-half its value as a heating agent.
Blue gas may be rendered luminous by the addition of some hydrocarbon
that will liberate free carbon in the flame when burned. This is
accomplished in the process of manufacture by the addition of vaporized

The following table as stated by Fulweiler gives the heating values of
the gases commonly used for domestic purposes in British thermal units
per cubic foot.

    Coal gas.                  622 B.t.u.
    Carburetted water gas      643 B.t.u.
    Pintsch gas.             1,276 B.t.u.
    Blau gas.                1,704 B.t.u.
    All-oil water gas          680 B.t.u.
    Acetylene gas            1,350 B.t.u.
    Gasoline gas.              514 B.t.u.
    Oil gas                  1,320 B.t.u.
    Blue water gas             300 B.t.u.

The cost and calorific values as computed by Dr. Willard of the State
Agricultural College of Kansas, given below, shows the relative values
of various kinds of domestic fuels.

                                              Cost per Cal. per Cal. for
                                                pound   Gram      1 cent

  Wood, 20 per cent. H.O. $ 5.00 per cord       0.167    2.3       7,620
  Bitu. coal              $ 4.25 per ton.       0.213    7.5      16,009
  Ant. coal               $12.50 per ton        0.625    6.0       4,354
  Gasoline, sp. gr. 68    $ 0.14 per gallon,
                                   5⅔ pounds.   2.470   10.0       1,846
  Kerosene, sp. gr. 80    $ 0.11 per gallon,
                                   6⅔ pounds.   1.650   10.0       2,753
  Coal gas, 1.50 per 1000 cubic feet.           3.100   20.0       2,927
  Alcohol, 90 per cent., 50 per gallon,         7.140    6.4         404
                                     7 pounds
  Electricity, 0.15 per kilowatt-hour                               57.4

The relatively high heat value of Blau gas (1704 B.t.u.) and the fact
that it may be reduced to a liquid form for transportation has resulted
in the manufacture of small lighting plants that may be used in places
where other forms of liquid or gaseous fuel are not desirable.

For transportation the gas is compressed in seamless, steel bottles
that contain about 20 pounds of liquid. The charged bottles
are shipped to the consumer and when empty are returned to the
manufacturers to be refilled.

The entire plant--ready to be attached to the distributing pipes in
the house--is contained in a steel cabinet. The charged tanks are
attached to a larger tank into which the liquid gas is first expanded.
This expansion is accomplished by an automatic valve that maintains
a constant pressure in the large tank. With this plant the lamps and
burners of the stoves are operated as with city gas--no generating or
preliminary preparation being necessary. As soon as the bottles are
exhausted they are replaced by others and the empty bottles are shipped
to the factory to be refilled.

=Measurement of Gas.=--When gas of any kind is purchased from a
manufacturing company, the amount used is measured by a gas meter,
located at the point where the gas main enters the building. The
readings of the meter are taken by the company at stated intervals and
the amount registered is charged to the account of the consumer. Gas
is sold in cubic feet and is so registered by the meter. The price is
quoted by the manufacturers at a definite rate per thousand cubic feet.
The difference between the last two readings of the meter furnishes the
amount from which the gas bill is reckoned.

The occupants of a building are responsible for all gas registered by
the meter and, therefore, should be acquainted with the conditions
under which the gas is sold. Gas bills are often the subject of dispute
because of failure to understand the period of time covered by the
amount claimed; again, the varying length of days due to the season of
the year has a pronounced effect on the amount of gas consumed. Lack of
care in the economical use of gas is probably the most prolific cause
of disputed bills.

The amount due for gas may at any time be checked by the consumer who
keeps a record of the meter readings. At any time the correctness of a
meter is doubted, arrangement may be made with the gas company to have
it tested for accuracy. This is done in the office of the company, by
attaching the meter to a measuring device--called a meter prover--in
which a definite measured amount of gas is passed through the meter and
comparison made with meter registration. If it is found that the meter
does not register correctly, the gas company is in duty bound to make
good the difference. If, however, the meter is found to be correct, it
is customary to charge for the services of proving the meter.

=Gas Meters.=--The gas meter as ordinarily used is shown in Fig. 177.
In Fig. 178 the same meter is shown with the top and front exposed.

[Illustration: FIG. 177.--Gas meter.]

[Illustration: FIG. 178.--Gas meter showing internal mechanism.]

The meter is operated by the pressure of the gas which enters at
the inlet pipe on the left-hand side of the meter as you face the
index. The gas from this pipe comes into the valve chamber and passes
alternately into the diaphragms and their chambers, as the valve ports
_V_ are opened and closed by the action of the meter. The movement
of the valve in opening the port which admits gas to the diaphragm
closes the port to the chamber which has filled. The gas entering the
diaphragm expands it like a bellows and forces the gas out of the
chamber, through the middle part of the valve into the outlet pipe _F_.
While this action is going on, the gas is entering the case compartment
on the opposite side of the meter and also forcing the gas from its
diaphragm through the opening _F_.

While the meter is in operation, one of the diaphragms and one of
the case compartments are filling while the others are emptying. The
movement of the diaphragm discs is transformed to the recording dial by
the connecting levers shown at the top of the figure. The movement of
these levers is such as to produce a rotary motion to a tangent which
is attached to a shaft that operates the recording dial. The tangent is
carried around in a circle by the action of the arms and its movement
is registered on the index of each cycle of the diaphragms.

The measurement is accomplished by the displacement of a definite
amount of gas with each movement of the discs; first, from the chamber
and then from the diaphragms.


The index of a gas meter looks quite complicated, but it is really
a very simple contrivance. The small circle on the top in Fig. 177
is for testing purposes only and need not be considered. The dial of
Fig. 177 is shown in Fig. 177_A_. The first circle, marked 1 thousand,
registers 100 feet for each figure, 1000 feet for the entire circle. If
the pointer stood on 9 it would mean 900 cubic feet. The second circle
registers 1000 for each figure, or 10,000 for the entire circle. When
the pointer of the first circle has been around once, it reaches 0 on
that circle, but the hand on the second has moved to figure 1, showing
1000 feet used. The process goes on until the pointer of the second
circle has traveled around and stands at zero. The pointer on the third
circle, however, has moved to 1, indicating 10,000. This explanation
shows the general plan of the index. A few minutes study of it will
render the index as easy to read as the face of a clock. Of course, the
pointers do not always stand exactly on the figures as they move from
figure to figure as the gas is used.

Suppose your index stood like this:

[Illustration: FIG. 177_A_.--Gas-meter dial. It reads 38600 cubic feet.]

Take the figure 3 on the 100 thousand circle, the figure 8 on the 10
thousand, and the figure 6 on the 1 thousand, and you have 30,000,
8000, and 600, or 38,600 feet. To ascertain the quantity of gas used
in the time elapsing between the readings of the meter, subtract the
quantity registered at the previous reading. Thus, if the previous
reading was 38,600 feet, and the next reading 40,100 feet, the pointers
standing thus:

[Illustration: FIG. 177_B_.--Gas-meter dial. It reads 40100 cubic feet.

    You have                          40,100
    Subtract your last reading        38,600 and you find
    that your bill should be for      1,500 feet

When 100,000 feet have been passed, the index is at zero; that is, all
the pointers stand at 0, and the registration begins all over again.

=Prepayment Meters.=--In many places it is desirable to sell gas in
small quantities and to prepay the amount for a given supply of gas.
This is accomplished by a meter such as that of Fig. 179. The meter is
constructed much the same as the former but provided with a mechanism
such that when a coin--usually 25 cents--is deposited, according to the
printed directions in the instrument, an amount of gas representing
the proportional current rate is allowed to pass the meter. The supply
is cut off as soon as the amount paid for is used; when in order to
receive more gas, another coin must be deposited as before.

[Illustration: FIG. 179.--The prepayment gas meter.]

=Gas-service Rules.=--The rules for the regulation of gas service are
in many States under the control of a board or commission whose duty
it is to form codes prescribing the measurement and sale of all public
utilities. The following form, General Order No. 20, State Public
Utilities Commission of Illinois, gives an idea of the requirements in
that State for the sale of coal gas.

     RULE 3. REQUEST TESTS.--Each utility furnishing metered service
     shall make a test of the accuracy of any meter, upon written
     request by a consumer: Provided, first, that the meter in question
     has not been tested by the utility or by the commission within 6
     months previous to such request; and second, that the consumer
     will agree to accept the result of the test made by the utility
     as determining the basis for settling the difference claimed.
     No charge shall be made to the consumer for any such test. A
     report, giving the result of every such test, shall be made to the

     RULE 4. ADJUSTMENT OF BILLS FOR METER ERROR.--If on any test of a
     service meter, either by the utility or by the commission, such
     meter shall be found to have a percentage of error greater than
     that allowed in Rule 11 (see below) for gas meters, the following
     provisions for the adjustment of bills shall be observed.

     (_a_) _Fast Meters._--If the meter is faster than allowable, the
     utility shall refund to the consumer a percentage of the amount of
     his bills for the 6 months previous to the test or for the time
     the meter was installed, not exceeding 6 months, corresponding
     to the percentage of error of the meter. No part of a minimum,
     service or demand charge need be refunded.

     (_b_) _Slow Meters._--If the meter is found not to register or to
     run slow, the utility may render a bill to the consumer for the
     estimated consumption during the preceding 6 months, not covered
     by bills previously rendered, but such action shall be taken only
     in cases of substantial importance where the utility is not at
     fault for allowing the incorrect meter to be in service.

     RULE 11. GAS-METER ACCURACY.--(_a_) _Method of Testing._--All
     tests to determine the accuracy of registration of a gas service
     meter shall be made with a suitable meter prover. At least two
     test runs shall be made on each meter, the results of which shall
     agree with each other within one-half per cent. (1/2%).

     (_c_) _Allowable Error._--Whenever a meter is tested to determine
     the accuracy with which it has been registering in service, it may
     be considered as correct if found not more than two per cent. (2%)
     in error, and no adjustment of charges shall be entailed unless
     the error is greater than this amount.

     RULE 15. HEATING VALUE.--Each utility furnishing manufactured
     gas shall supply gas which at any point at least 1 mile from the
     plant, and tested in the place where it is consumed, shall have a
     monthly average total heating value of not less than 565 B.t.u.
     per cubic foot, and at no time shall the total heating value of
     the gas at such point be less than 530 B.t.u. per cubic foot.

     To arrive at the monthly average total heating value, the results
     of all tests made on any one day shall be averaged and the average
     of all such daily averages shall be taken as the monthly average.

     RULE 8. RAILROAD COMMISSION OF WISCONSIN.--Each utility furnishing
     gas service must supply gas giving a monthly average of not less
     than 600 B.t.u. total heating value per cubic foot, as referred
     to standard conditions of temperature and pressure. The minimum
     heating value shall never fall below 550. The tests to determine
     the heating value of the gas shall be made anywhere within a
     1-mile radius of the center of distribution.

=Gas Ranges.=--Gas ranges and all other heaters using gas as a fuel
are constructed to utilize the principle of the Bunsen burner. Fig.
180 illustrates the type of burner used in the Jewel gas range. This
represents the form adapted to the top burners for all direct-contact
cooking or heating. The burners are of different sizes and arranged as
they appear in Fig. 181. This picture shows the top of the range as
seen from above, looking directly downward. The gas supply pipe and
individual valves for each burner are in position as they appear in
front of the range.

[Illustration: FIG. 180.--Detroit Jewel one-piece, star-shaped burner.]


FIG. 181. FIG. 182.

FIG. 181.--Showing top burners and valve attachment of a gas stove.

FIG. 182.--Section showing arrangement of oven burners and lighter of a
gas oven.]

In operation, the nozzles of the gas valves stand directly in front of
the opening _G_, in Fig. 180. The stream of gas in passing into the
burner induces a flow of air through the opening _A_. The mixture of
gas and air is such as will burn with the characteristic Bunsen flame
without smoke.

The oven burners are different in form but the individual flames are
the same as those of the top burners. They extend across the oven as
shown in Fig. 182. In this the top of the oven is removed and burners
as seen are viewed from above.

The top burners are lighted by direct application of a burning match
but the oven burners must be lighted by first igniting a special torch
or “pilot lighter.” The middle gas valve of Fig. 182 is turned and
the torch lighted, then the other valves are opened and the jets are
instantly ignited. As soon as they are burning the pilot lighter is
extinguished by turning its valve.

The reason for this special lighter is because of the possibility of
explosion at the time of lighting. The gas from the jets is mixed with
air at the proper proportion to be violently explosive and if by chance
the gas should be turned on a sufficient time to fill the oven with
this explosive mixture and then lighted, an explosion would be certain,
with every possibility of disastrous consequences. All gas ovens should
be lighted in a manner similar to that described.

=Lighting and Heating with Gasoline.=--The remarkable growth of modern
cities, the building of small towns in the west, and the improvement
in suburban and rural homes has created a demand for efficient means
of illumination in the form of small household lighting plants. The
development and improvement in electric lighting has induced an equal,
if not greater, improvement in gas lighting. Up to the year 1875, the
open-flame gas jet represented the most improved form of city lighting.
Then came electricity, which for a time bade fair to supplant all other
forms of illumination; but the relative high cost of electric lighting,
even with the advantages it afforded, was a stimulus to improvement in
less expensive forms of illuminants.

The invention of the incandescent-mantle gas burner enormously
increased the opportunities for gas lighting and opened an inviting
field of endeavor. In a relatively short time, three distinct types of
gasoline lighting plants for household illumination came into common
use, with a great number of different systems in each type. As a means
of economical illumination the only rival of any consequence to the
small gasoline-gas plant of today is acetylene. The dangers attending
the use of these agents of illumination have been rapidly eliminated,
until today--when intelligently managed--they are fully as safe as any
other means of artificial lighting. Gasoline plants are now in common
use in cities where competition with all other forms of illumination
require excellence in service to hold an established place.

In order that any mechanical appliance may be used with the best
results, its principle of operation and mechanism must be thoroughly
understood. In the case of gasoline plants, not only familiarity
with the mechanism should be acquired but an intimate knowledge of
gasoline and its characteristic properties should be gained, that the
peculiarities of the plant may be more fully comprehended.

=Gasoline= is the first distillate of crude petroleum; that is, in the
process of separation, the crude petroleum is distilled from a retort
and the condensed vapors at different degrees of temperature form the
various grades of gasoline, kerosene, lubricating oil, paraffin, etc.
The crude oil is placed in the still and heated; the distillate that
first comes from the condenser, at the lowest temperature of the still,
is gasoline of a light spiritous nature. As the process of distillation
continues, this part of the petroleum is entirely driven off and it is
necessary to raise the temperature of the still in order to vaporize an
additional portion of the oil. There is no distinct line of separation
between the gasoline that first comes from the condenser and that which
comes over after the temperature is raised, except that it is less of a
spiritous nature and contains more oily matter. As the temperature of
the retort is gradually raised, the distillate contains less and less
of the spiritous and constantly more of the oily matter.

In order to grade gasoline for the market, the standard adopted was
that of relative density. The distillations produced at various
temperatures are mixed to produce various densities which form
definite grades of gasoline. The Beaumé hydrometer is a scale of
relative specific gravities in which the different densities are
expressed in degrees. The highest grade of gasoline produced by the
first distillation is 90°Bé.; that is, the hydrometer will sink in
the gasoline to 90° on the scale. As the temperature of the retort
is gradually raised, the distillate becomes heavier and the next
commercial grade is 86° gasoline. The 86° gasoline contains a greater
proportion of oily matter and a less amount of that of a spiritous
nature. The next commercial grade that is produced, as the temperature
is raised, is 76° gasoline, a still highly volatile spirit but
containing more oil than the last. This process is kept up until there
is an amount of oil in the distillate that can no longer be termed
gasoline, when kerosene is distilled from the retort.

The following descriptions of gasoline and kerosene by B. L. Smith,
State Oil Inspection Chemist of North Dakota, gives a definite idea of
their properties and the requirements of the law in their regulation
and sale.

     “Gasoline is formed by the condensation of vapor that passes
     off at comparatively low temperatures during the distillation
     of crude petroleum. It has been common practice among refiners
     to collect as ‘straight’ gasoline all that distillate having
     a specific gravity above 60°Bé. At present, the name applies
     broadly to all the lighter products of petroleum above 50°Bé. in
     gravity, including products obtained from the ‘casing-head’ gases
     of oil wells, by methods of compression and cooling, and also the
     ‘cracked’ gasoline formed by the decomposition of heavier oils
     when subjected to high temperature and pressure.

     “It has been the custom to grade and sell gasoline according to
     ‘high’ or ‘low’ gravity test. Recent study and investigation has
     shown that specific gravity in itself is of very little value in
     determining the quality of a gasoline. It may be taken as an index
     of other properties, particularly its volatility, if information
     as to its source and method of production are at hand; but under
     present market conditions a specific-gravity determination is
     entirely inadequate. The specific-gravity test alone may give a
     high rating to a poor gasoline and a low rating to a good one. It
     has been discarded as a standard of comparison by the U. S. Bureau
     of Mines. It indicates nothing definite about the quality of a
     gasoline and in many cases it does not even approximate relative
     values. Volatility, that is, the ease with which it vaporizes, is
     the fundamental property that determines the grade, quality, and
     usefulness of gasoline. The Beaumé test, however, must remain the
     standard for grading gasolene until a more definite measure is

     “The Oil Inspection Law (1917) for the State of North Dakota,
     states, that: ‘all gasolines, sold or offered for sale in
     this State for household use, shall, when one hundred cubic
     centimeters are subjected to a distillation in a flask--as
     described for distilling of oil--show not less than three (3) per
     cent. distilling at one hundred and fifty-eight (158) degrees
     Fahrenheit, and there shall not be more than six (6) per cent.
     residue at two hundred and eighty-four (284) degrees Fahrenheit,
     which shall be known as the chemical test for gasoline sold or
     offered for sale in this State for domestic purposes.’

     “Gasoline for household purposes, as for use in cold-process
     lighting systems should contain not more than a very slight amount
     of constituents that do not vaporize readily. It is obvious that
     a gasoline for cleaning or drying purpose should contain no oily
     or kerosene distillate. On the other hand, the gasoline for use
     in a gasoline stove or other generator, where heat is employed in
     its vaporization, may contain a considerable amount of the less
     volatile oils. The amount of gasoline sold for household use is
     in very minor proportion to the immense quantity used for motor

     “No hard and fast line differentiates good motor gasoline from
     bad. In fact standards of quality seem to be varying with advances
     in engine design, so that what once was poor gasoline can now be
     successfully used. Improvement in carburetors seem to be keeping
     pace with the ever increasing amount of kerosene in the ordinary
     motor gasoline.

     “Gravity test cannot be relied upon as indicating the kerosene
     content. In the laboratories of the Oil Inspection Department for
     the State of North Dakota, there have been examined two gasolines
     of the same gravity, 56.2°Bé. at 60°F., but which contains 31
     per cent. and 62 per cent. of kerosene respectively, and their
     distillation range is quite different. On the other hand, there
     are other gasolines whose boiling range is nearly parallel
     and similar, yet whose gravities are 50.2°Bé. and 59.2°Bé.
     respectively. Also a gasoline and a kerosene having a difference
     in gravity of but 1°Bé. and a difference of nearly 100°F. in the
     temperature at which they begin to boil and a difference at 200°F.
     in the temperature at which all had distilled over. The so-called
     ‘low’-test gasolines average between 35 per cent. and 40 per
     cent. kerosene. The chief element of advantage in the so-called
     ‘high’-test gasolines seems to be that they yield a maximum
     efficiency over a larger range of engine conditions.

     “We have a sample of gasoline sold as ‘high’-test gasoline which
     contains 29 per cent. of kerosene. Indeed it has a high Beaumé
     gravity (63.70) compared to the average low-gravity gasolines on
     the market, and it also contains a large amount (14 per cent.)
     of very easily volatile constituents. Such a product seems to be
     a blend of very light ‘casing-head’ stock with kerosene of low
     boiling range to give the ‘high’ gravity.

     “It is desirable that a gasoline should contain a certain
     percentage of very low-boiling constituents, so that engines
     may start more readily, especially in unfavorable conditions of
     weather or climate; but a large proportion would be undesirable
     because of loss through evaporation and the liability of
     accidental ignition and explosion. A reasonable amount of light
     volatile material would probably be about 3-1/2 per cent. Again a
     reasonably low percentage of the very less volatile constituents
     is desirable to insure complete vaporization at a not too high
     temperature, say not more than 10 per cent.; but such a gasoline
     would be expensive. The producers and refiners claim that the
     present immense demand necessitates the mixture of low-boiling
     kerosene constituents with the true gasoline fraction.

     =“Kerosene.=--The character of this fuel is best understood by
     comparing it with gasoline, which it in general resembles, except
     that it is much less volatile. It is obtained from crude petroleum
     at a temperature just above that (300°F.) at which gasoline passes
     off. Its chief use is as an illuminant in lamps. It is also
     increasingly used as a fuel in cooking stoves, small portable
     heaters, and as a motor fuel for engines and tractors.

     “The laws of most States stipulate certain tests which kerosene
     must meet in order to be approved for general sale. These tests
     include color, flash point, fire test, sulphur determination, and
     candlepower tests. The North Dakota Oil Inspection Law (1917)
     specifies that the color shall be water-white when viewed by
     transmitted light through a layer of oil 4 inches deep. It shall
     not give a flash test below 100°F. and shall not have a fire test
     below 125°F. Such illuminating oils shall not contain water or
     tar-like matter, nor shall they contain more than a trace of any
     sulphur compound. The photometric test, when burning under normal
     conditions, shall not show a fall of more than 25 per cent. in
     candlepower in a burning test of not less than 6 hours nor more
     than 8 hours’ duration, consuming 95 per cent. of the oil.

     “The flash point of an oil is the lowest temperature at which
     vapors arising therefrom ignite, without setting fire to the oil
     itself, when a small test flame is quickly approached near the
     surface in a test cup and quickly removed.

     “The fire test of an oil is the lowest temperature at which the
     oil itself ignites from its vapors and continues to burn when a
     test flame is quickly approached near its surface and quickly

     “When oils containing sulphur are burned, the sulphur is thrown
     off in the form of gaseous sulphur compounds. Because of their
     poisonous nature and their bleaching and disintegrating action on
     clothing, hangings, wall coverings, etc., it is obvious that to
     safeguard the health and preserve the furnishings of the home,
     illuminating oils should contain not more than a trace of sulphur
     compounds, and that their flash and fire limits should be high
     enough to insure safety in ordinary use in lamps and stoves.

     “The law further specifies as to the boiling limits of kerosene:
     ‘It shall be the duty of the State Oil Inspector ... to have
     chemical tests made ... demonstrating whether or no such oils
     contain more than 4 per cent. residue after being distilled at a
     temperature of 570°F., and shall not contain more than 6 per cent.
     of oil distilling at 310°F., when one hundred cubic centimeters of
     the oil is distilled from a side-neck distilling flask’ of certain
     specified dimensions.

     “This is to insure the kerosene against an excess of easily
     inflammable material of the gasoline range and thus render it
     dangerous to the user. In addition it is to insure against
     an undue proportion of heavy constituent of lubricating oil
     distillate, which would clog the wick and reduce the efficiency,
     heating and illuminating value of the oil.”


The extended use of gasoline as a lighting and heating agent, has
brought about the development of a great number of mechanical devices
that are intended to furnish the house with an efficient source of
illumination and at the same time provide the kitchen with a convenient
and relatively inexpensive fuel. These machines are generally simple
in mechanical construction and so designed as to eliminate most of the
dangers involved in the use of gasoline. In operation, they require a
minimum amount of attention when suited to the purpose for which they
are intended. That the object of the plants is attained is attested by
the great number in use and the degree of satisfaction afforded the

The three systems of gasoline lighting referred to above are known
commercially by terms which are characteristic of the process involved:

1. The _cold-process_ system, in which the gasoline is vaporized,
at the temperature of an underground supply tank, and after being
mixed with the required amount of air is sent through the building in
ordinary gas pipes exactly as in the case of city gas.

2. The _hollow-wire_ system, in which the gasoline is sent from the
supply tank to the burners in a liquid form, where it is vaporized by
heat and the vapor mixed with the necessary air to afford complete

3. The _central-generator_ or _tube_ system, in which the gasoline is
sent to a central generator from a supply tank and there vaporized by
heat, at the same time being mixed with air in sufficient amounts to
render it a completely combustible gas without further dilution.


The gas machine of the cold-process type is so constructed that air is
forced through a tank or carburetor, containing gasoline and remains in
its presence until saturated with gasoline vapor. This saturated air
is afterward diluted with additional air, to produce a quality of gas
that contains proportions of air and gasoline vapor which will produce
complete combustion when burned with an open flame.

Combustion is a rapid chemical change in which heat is evolved due to
the union of carbon and oxygen. If the carbon is completely oxidized,
the combination produces carbon dioxide (CO₂) and the greatest amount
of heat is evolved.

Gasoline being a highly volatile liquid will vaporize at temperatures
as low as -10°F., but as the temperature is higher vaporization will be
more rapid. In a confined space, at relatively low temperature, such
as the carburetor of a gas machine, the vaporization will at first
be very rapid; but after the more highly spiritous portion has been
evaporated, a considerable part, even of the lighter grades, will be
vaporized very slowly. In the cold-process machines, only the lighter
grades can be used with success and even then, in inefficient machines,
a portion of the lesser volatile gasoline will have to be thrown away.
For this reason and for others that will appear later, it is advisable
to consider very closely the working properties of the entire plant.

In order to obtain gas that will always be of the same quality and at
the same time use gasoline in an efficient manner, the gas machine must
be composed of three essential parts: the blower, the carburetor and
the mixer.

The blower is that part of the machine which supplies air for absorbing
the gasoline vapor and maintaining a constant pressure on the system.
It is usually made in the form of a rotary pump, the motive power for
which is a heavy weight. The pump may, however, be driven by water
pressure furnished by city water pipes or other water supply.

The carburetor is a tank which contains the supply of gasoline and is
so constructed as to permit the air from the blower to most readily
take up the gasoline vapor. It should be so arranged that when the
contained gasoline becomes old and less volatile, the air may remain in
its presence a sufficient time to become saturated by slow absorption.

The mixer is that part of the machine which regulates the amount of
gasoline vapor contained in the gas entering the distributing pipes. In
order to satisfactorily perform its function, it should be so arranged
as to permit a constant amount of gasoline vapor to enter the mixture
which composes the finished gas. This amount should be such as to
produce a bright clear flame in an open gas jet. If the gas contains
too great an amount of gasoline vapor, the flame will smoke. If too
little gasoline vapor is present, the flames will be pale and lacking
in heat.


    1 Carburator
    2 Mixer
    3 Blower
    4 Weight
    5 Gas Range
    6 Water Heater
    7 Water Tank

FIG. 183.--Cold-process system of gasoline lighting with kitchen range
and water heater.]

In Fig. 183, the entire plant is shown in place. It occupies a place
inside the building, usually in the basement. In the figure the
carburetor is marked 1; the mixer 2 stands at the end of the blower,
which is numbered 3. The motive power of the blower is furnished by
a heavy weight, which is raised by a block and tackle, the cord of
which is attached to the drum and fastened to the shaft of the blower.
The force furnished by the weight 4 drives the blower and maintains a
constant pressure on the gas in the system. The pipe 8 conducts the air
from the blower to the carburetor, which is located underground, below
the frost line and 25 or 30 feet away from the building.

[Illustration: FIG. 184.--Carburetor for cold-process gasoline lighting

The carburetor in this case is also the storage tank, as shown in
detail in Fig. 184. The carburetor is divided laterally into two
or more compartments, depending on the size of the plant to be
accommodated. That shown in Fig. 184 contains four compartments and
is intended for a large plant. The construction is such that the
compartments are only partly filled with gasoline, and arranged to
permit the air from the blower, which enters at the pipe marked air, to
pass through each compartment in succession, beginning at the bottom,
in order that it may become completely saturated with gasoline vapor.
As an additional means of aiding the saturation of the passing air,
the compartments in this carburetor are provided with spiral passages
through which the air must pass, so that when it reaches the outlet
pipe, marked gas, the air is completely filled with gasoline vapor.

The vapor-saturated air now leaves the carburetor by pipe 9, in Fig.
183, and enters the mixing chamber 2, where it is mixed with the
required amount of atmospheric air, to make it completely combustible
when burned at the burner.

The mixing chamber is shown in detail in Fig. 185. The mixing is done
automatically and the quality of the gas is uniform, regardless of the
varying conditions of the attending temperature and the quality of the
gasoline in the carburetor.

The vitally important feature of any gas machine is, that a constant
amount of gasoline vapor be carried to the burners. If the gas contains
too great an amount of gasoline vapor, a smoky flame will be the
result; if an insufficient amount of gasoline is present, the flame
will be pale and give out little light. When freshly charged, the
gasoline in the carburetor will vaporize very readily, and a large
amount of air must be added to the gas to reduce it to the proper
consistency; but from old gasoline, which has lost most of the highly
volatile matter, a smaller proportion of atmospheric air will be
demanded. For this reason, a mixing regulator that will always deliver
gas containing the same amount of gasoline vapor is necessary to give
satisfactory service. The mixer shown in Fig. 185 accomplishes this
office by reason of the specific gravity of the gas.

As the air in the carburetor takes up gasoline vapor, its specific
gravity is increased until the air is saturated; and by adding the
amount of atmospheric air necessary for complete combustion the weight
is reduced to a definite amount which will be constant. The required
mixture will, therefore, always weigh the same amount. The principle on
which this mixer works is that described in physics as the principle
of Archimedes: “that a body immersed in a fluid will lose in weight an
amount equal to the liquid displaced.” In the application of the law,
the gas in the mixer is the fluid, and the float--to be described--is
the displacing body.

[Illustration: FIG. 185.--Diagram illustrating the mixer of the Detroit
cold-process system of gasoline lighting.]

The mixer in Fig. 185, is shown cut across lengthwise. The outside
casing is indicated by the heavy black lines. The gas which leaves the
opening at the top--marked gas outlet--is a mixture of gasoline and air
that may be used for exactly the same purpose and in the same manner
as coal gas. It may be used in open-flame gas jets or in the mantle
gas lamps for lighting purposes and also as fuel gas for domestic
heating. The gas is distributed through the building in ordinary gas
pipes which are installed as for any other kind of gas. In Fig. 183 the
distributing pipes are indicated by the heavy lines.

The valve in the air inlet, in the bottom of the mixer, controls the
amount of air to be admitted. The entering gas from the carburetor
being heavier than the desired mixture, will raise the float and in
so doing will open the air valve and allow the air from the blower to
enter. The float and valve are so adjusted that the desired mixture is
attained when the balance beam is level. Any variation in the mixture
will change its weight and the valve corrects the change whether it be
too much or too little air.

The openings at the bottom, marked _gas inlet_ and _air inlet_, are
intended for the admission of the saturated vapor from the carburetor,
and the atmospheric air, as required. The float which fills the greater
part of the inner space is a light sheet-metal drum, that is tightly
sealed and nicely balanced by a counterweight on the opposite end of
the suspending bar. The counterweight is made adjustable by the device
marked _movable adjusting weight_--in the drawing--which permits the
quantity of entering gas to be slightly changed as the gasoline in the
carburetor grows old.

The adjustment of the counterweight to suit the gas given off from
old gasoline in the carburetor, and the occasional rewinding, to
elevate the blower weight, is practically all the attention this plant
requires. It is a real gas plant which gives every service that may be
obtained from coal gas.


The hollow-wire system of gasoline lighting possesses the advantage
of simplicity in construction and ease of installation that makes it
attractive, particularly for use in small dwellings. The ease with
which plants of this character are installed in buildings already
constructed and its relatively low cost has made it a popular means
of lighting. The same principle as that used in the hollow-wire system
is applied to portable gasoline lamps in which a remarkably convenient
and brilliant lamp is made to take the place of the customary kerosene
lamp. Small portable gasoline lamps are now extensively used for the
same purpose as ordinary oil lanterns. These lamps are convenient
as a source of light, make a handsome appearance and are relatively
inexpensive to operate.

[Illustration: FIG. 186.--Hollow-wire system of gasoline lighting with
gravity feed.]

The hollow-wire system as commonly employed is illustrated in Figs. 186
and 187. In the gravity type of the system as illustrated in Fig. 186,
the supply of gasoline is stored in the upper part of the house in a
tank _T_ and conducted to the burners below, through a system of small
copper tubes as indicated by the heavy lines in the drawing. The same
tank is used to supply the gasoline for the stove _R_ in the kitchen
and the lamps _L_ in the different apartments. The gasoline supply in
this case, is obtained entirely by gravity. This type of plant is not
approved by the National Board of Underwriters but its use is quite
generally permitted. The storage of gasoline in this form should be
done with caution as carelessness or accident might lead to serious
results. With an arrangement of this kind the force of gravity gives
the pressure which supplies the burners below but it would not be
possible to use the lamps on the same floor with the tank.

[Illustration: FIG. 187.--Hollow-wire system of gasoline lighting with
pressure-tank feed.]

Where it is desired to use lamps on both floors, a pressure tank is
employed for supplying the gasoline to the lamps, as indicated in Fig.
187. In this plant the pressure tanks _S_, _T_ in the basement, furnish
the pressure which forces the supply of gasoline through the small
tubes to the lamps _L_ in the different rooms and also to the stove _R_
in the kitchen.

The means of furnishing the pressure for supplying the gasoline to the
burners may be a simple tank as that in Fig. 188, or the more elaborate
apparatus shown in the double tank of Fig. 189. Either style will
give good results but the double tank requires the least attention in
operation and is therefore more satisfactory in use.

The tank in Fig. 188 is made of sheet metal of such weight as will
safely withstand the pressure necessary in its use. It is arranged
with an opening _E_, for filling with gasoline, a pressure gage for
indicating the air pressure to which the gasoline is subjected, and two
needle valves; _C_, for attaching an air pump and _D_, to which the
hollow wire is attached for distributing the gasoline to the places of
use. The tank is filled with gasoline to about the line _A_, and then
air pressure is applied with an ordinary air pump to say 20 pounds to
the square inch. This pressure will be much more than will be necessary
to force the gasoline through the tubes but it is intended to last for
a considerable length of time.


FIG. 188.--Simple gasoline pressure-tank.

FIG. 189.--Double-pressure tank for constant pressure service in
gasoline lighting systems.]

The principle of operation is that known in physics as Boyle’s law,
that “the temperature being constant, the pressure of a confined gas
will be inversely as its volume.” That is, if the tank is perfectly
tight, the pressure above the line _A_, in the tank, will gradually
become less as the gasoline is used and when its level is at the line
_B_, where the volume is twice the original amount, the pressure will
be one-half what it was originally, and will still be sufficient to
force the gasoline through the tubes to the lamps. It is evident that
once the tank is charged and the air pressure applied it will require
no further attention until a considerable part of the gasoline is
consumed. If at any time the pressure in the tank becomes too low to
feed the lamps, a few strokes of the pump will raise it to the required

While the single tank does the required work, its use is not perfect
because the pressure is constantly varying. If a lamp is set to burn at
a definite pressure, any decrease in the gasoline supply due to falling
pressure will change the amount of light given by the lamp; while the
variation in the pressure of the single supply tank is not great, a
more perfect effect is attained in the double type of tank as that of
Fig. 189.

The object attained in the use of two tanks differs with different
manufacturers. The tank shown in Fig. 183, being intended to maintain
a constant pressure on the gasoline, is quite different from those
described in Fig. 197 in use with the central-generator system of
lighting, to be described later. In Fig. 189 tank No. 1 is for air
supply alone and tank No. 2 is the storage tank for gasoline. Between
the two tanks is a pressure-regulating valve 6-7, which keeps a
constant pressure on tank No. 2 so long as the air pressure of the tank
No. 1 is equal or greater than the other. The gasoline in tank No. 2
will therefore be always under the same pressure and when the lamps are
once burning the gasoline supply to each lamp will be a constant amount.

Tank No. 2 is separated by the head 13 into two compartments, marked
18 and 19. The connection between the two compartments is made by the
valve 15 and the connection 16. The gasoline supply for the lighting
system is taken from the lower chamber at the valve marked 17.

It is possible to refill this tank with gasoline while the system is
working. To accomplish this, the air supply is cut off from tank No. 1,
by closing valve 9 and the valve 15 is closed to retain the pressure on
the lower chamber of tank No. 2. The screw-plug is then taken from the
tube 12 and the tank refilled. The screw-plug is then returned to its
place, the valves 9 and 15 are again opened and the regulating valve
immediately restores the desired pressure.

The amount of pressure required on the system will depend on the height
to which the gasoline is carried within the building. The pressure is
generally 1 pound to each foot in height and to do the best work the
pressure must be constant.

These plants may serve as a fuel supply for gasoline stove as indicated
at _R_ or any other source of domestic heating. The usual gravity
supply tank is replaced by the hollow wire through which is the
gasoline from the tank in the basement.

=Mantle Gas Lamps.=--Mantle lamps that are intended for using
city gas are much the same in construction as those using the
cold-process gasoline gas; the styles of mechanism differ somewhat
with manufacturers but all lamps of this kind possess the essential
features that are common to all. Either of these gases may be used
with open-flame burners, such as Fig. 193, but since the introduction
of mantle lamps, the open-flame burners are rarely used for household

In the incandescent-mantle lamp, the light is produced by heating to
incandescence a filmy mantle of highly refractory material. The higher
the temperature to which the mantle of a lamp is raised, the greater is
the quantity of light produced. The office of the burner is to produce
a uniform heat throughout the mantle with the use of the least amount
of gas. As ordinarily furnished from the mains, coal gas or gasoline
gas is too rich in carbon to be used in mantle lamps without dilution.
When gas is burned in a mantle lamp, it must contain sufficient
oxygen--which is supplied by the air--to combine completely with the
contained carbon and reduce it to carbon dioxide. If insufficient air
is supplied, the lamp will smoke and the mantle will soon be filled
with soot.

In the use of the various gases--made from coal, gasoline, kerosene,
alcohol, etc.--as a fuel for the production of either heat or light,
the form of the burner in which the gas is consumed is the most
important factor of the system. Without burners in which to generate
a satisfactory supply of heat for the desired purposes, mantle gas
lamps would never have come into common use. An understanding of the
mechanism of the burners of a system is of first importance because of
the possibility of the failure of the entire plant through an improper
adjustment of the lamps.

If complete combustion of the gas is attained in the burner, the
greatest amount of heat will be evolved and the residue will be an
odorless gas, carbon dioxide (CO₂). If the gas is not completely
burned the odor of the gas is noticeable in the air. Incomplete
combustion may be caused by an insufficient air supply, which causes a
smoky flame; or if a larger flame is used than the burner is designed
to carry, some of the gas will escape unburned. In either case the
greatest amount of heat is not developed by the burner.

In most burners, whether for heating or lighting--in which gas,
gasoline or alcohol is used as a fuel--the principle of operation is
that of the Bunsen tube. One noticeable exception to this rule is the
burners used with the central-generating systems where the Bunsen tube
is a part of the generator.

The gas generated from any hydrocarbon will burn completely, only after
being mixed with air or other incombustible gas, in proportions such as
will completely oxidize the carbon contained in the fuel.

In Fig. 190 the familiar laboratory Bunsen burner affords an excellent
illustration of the Bunsen principle which forms a part of all burners
using gas as a fuel. The gas from the supply pipe issues from a small
opening _A_ into a tube _B_ and by the force of its velocity the
entering gas carries into the tube above it a quantity of air that may
be regulated by the size of the opening. If the gas is burned without
being first mixed with air, the flame will be dull and smoky but if
air is admitted to mix with the gas, an entirely different flame is
produced, the characteristic shape of which is shown in the figure.

[Illustration: FIG. 190.--Cross-section of Bunsen burner showing
characteristic Bunsen flame.]

The upper part of the flame _C_ is known as the reducing flame; it
is blue in color and intensely hot. The portion _D_ is the oxidizing
flame; it is pale blue, sometimes light green in color. The lower
part _E_ is the gas before it begins to burn. When burning in air,
the Bunsen flame gives scarcely any light, all of the energy being
expended in heat. In the gas stove where the burners are made up of a
great number of small jets, it will be seen that each jet shows the
characteristic features of the Bunsen flame.

The incandescent-mantle gaslight takes advantage of the heat generated
by the Bunsen flame and produces an incandescent light that has
revolutionized gas lighting. The flame of the Bunsen tube is burned
inside a mantle which is rendered incandescent by the heat.

The incandescent mantle was invented by Dr. Auer von Welsbach and was
known for a long time as the Welsbach light; but improvements in the
process of making the mantles, brought other lamps of the same type
on the market, when it became known as the mantle lamp. The first
serviceable mantles were made in 1891 and from that time there has been
a steady development in the gas-lighting industry.

The original mantles were made of knitted cotton yarn, impregnated
with rare earths and are still so made; but the most durable mantles
are now constructed from ramie or china grass. After being knitted,
the mantles are impregnated with thorium nitrate, with the addition of
a small quantity of cerium nitrate, and occasionally other nitrates.
The mantles are then shaped and mounted; the fiber is burned out
and the mantles are dipped in collodion to give them stability for
transportation. When placed in the lamp for use, the collodion is first
burned off and the remaining oxide of thorium forms the incandescent
mantle. One style of mantle is now being made in which the fiber is not
burned out until it is placed in the lamp. They are commonly used with
gasoline lamps and give very good results.

[Illustration: FIG. 191.--Gas lamp with upright mantle.]

The first incandescent-mantle gas lamps to be used were of the upright
type, such as is shown in Fig. 191, and for a long time they were
the only mantle lamps in use. While the upright mantle was a great
improvement over the open-flame gas jet, the lamp was not satisfactory
because of the shadows cast by the fixture and from the fact that a
large amount of the light was lost by being directed upward from the
incandescent mantle.

With the development of the inverted type, the mantle lamp was greatly
improved. In the use of lamps of any kind, the desired position of the
illumination is that in which the light is directed downward. In the
inverted type of mantle lamp this feature is accomplished and adds
materially to the efficiency of the light, because the rays are sent
in the direction of greatest service. The upright mantle lamps are
still sold but by far the greater number offered for sale are of the
inverted type.

The essential features of all gas lamps used under these conditions are
shown in Fig. 192, which represents the common bracket type of lamp.
The gas-cock _C_, connects the lamp with the gas supply _G_. The gas
escapes into the Bunsen tube, through an opening in the tip _P_, which
is so constructed that the amount of gas may be varied to suit the
required conditions. The brass screw nut _N_ may be raised or lowered
and thus increase or diminish the amount of escaping gas by reason of
the position of the pin _P_. If the nut is screwed completely down the
pin closes the opening and the gas is entirely shut off. When the lamp
is put in place, the burner is adjusted to admit the proper amount of
gas and so long as the quality of the gas remains the same, no further
adjustment will be necessary. Any change to a richer or poorer gas
will, however, require an adjustment of the burner to suit the mantle.
The amount of gas admitted is only that which will produce complete
combustion in the mantle when combined with the required amount of air.
Each burner must, therefore, be designed for the mantle in use.

[Illustration: FIG. 192.--Mantle gas lamp showing details of Bunsen

As the gas leaves the opening above the pin _P_, it enters the mixing
chamber of the Bunsen tube and air is drawn at the openings _A_-_A_.
The mixture of the gas and air is accomplished in the tube leading
to the mantle _M_, where it is burned. In all lamps of this kind,
there is a wire screen placed relatively as _S_, the object of which
is to prevent the mixture in the tube from exploding--in case of low
pressure--and thus cause the gas to ignite and burn at the point of
entrance to the tube.

At any time the pressure is insufficient to send a steady flow of gas
into the tube, the flame may “flash back” and ignite the gas at the
point of entrance where it will continue to burn. If, however, the
screen is interposed between the gas supply and the burner, the flame
of explosion will not pass the screen.

In lighting the lamp, the gas is turned on and a lighted match is held
under the mantle, the explosive mixture of gas and air fills the mantle
and escapes into the globe, in which it is usually inclosed. As soon
as ignition takes place the gas outside the mantle explodes with the
effect that is startling but not necessarily dangerous. The escaping
gas continues to burn and heats the mantle to incandescence.

The amount of escaping gas is regulated by turning the gas-cock to
produce the greatest brilliance with the least flame outside the
mantle. When used for household illumination, the intensity of the
light is such as to be objectionable, when used directly; but when
surrounded by an opal glass globe to diffuse the light, this is a
highly satisfactory and economical means of lighting.

=Open-flame Gas Burners.=--Gas jets of the open-flame type continue
to be used to some extent but the more efficient mantle lamp has very
largely supplanted lights of this kind. In the past, these gas lights
were made in a great many styles and were known under a variety of
trade names--the fish-tail burner, the bats-wing burner and the Argand
burner--and were at times very generally used for gas lighting.

[Illustration: FIG. 193.--Swing-bracket gas lamp with open-flame

The common gas jet is illustrated in Fig. 193. The figure shows a
bracket fixture which is generally fastened to a pipe in the wall. A
swing-joint at _A_ permits the flame _F_ to be moved into different
positions. The annular opening _A_ permits the gas to pass to the jet
in any position to which the light is moved. The gas-cock _C_ is a
cone-shaped plug, which has been ground to perfectly fit its socket.
It should move with perfect freedom, and yet prevent the escape of the
gas. A slotted screw _N_ permits the joint to be readjusted, should the
plug become loose in the socket.

The gas-tips _T_ are made of a number of different kinds of materials
and are commonly termed lava-tips but tips for gas and gasoline are
frequently made of metal. The bottom of the tip is cone-shaped, which
permits it to be forced into place in the end of the tube with a pair
of pliers. In size the tips are graded by the amount of gas which they
will allow to escape in cubic feet per hour. For example--a 4-foot tip
will use approximately 4 cubic feet of gas per hour. They are made in a
number of sizes to suit the varying requirements.

=The Inverted-mantle Gasoline Lamp.=--The inverted-mantle gasoline-gas
lamp shown in Fig. 194, furnishes a good example of mechanism and
principle of operation, when used with the hollow-wire system. This
is the bracket style of lamp but the same mechanism is used in other
forms of fixtures. Lamps of similar construction are suspended from the
ceiling, either singly or in clusters; they are also used in portable

[Illustration: FIG. 194.--Sectional view of hollow-wire mantle gasoline

In Fig. 194 the lamp consists of a bracket _H_, which is secured to the
wall and through the stem of which the gasoline is conducted to the
generator by the pipe _W_. The arrows show the course of the gasoline
and its vapor as it passes through the lamp. On entering the generator
the gasoline first passes, the percolation, through an asbestos wick
_B_, the object of which is to prevent the vapor pressure from acting
directly on the gasoline in the supply tube. The gasoline passes
through the wick _B_, largely by capillary action, as it must enter the
generator against a pressure greater than that afforded by the pressure
tank. The vaporization of the gasoline takes place in the tube above
the mantle _T_, from the flame of which it receives the necessary heat.

In lighting the lamp an asbestos torch saturated with alcohol is
ignited and hung on the frame, so that the flame may heat the
generating casting _N_. This process usually requires less than a
minute, generally about 40 or 50 seconds. The torch supplies heat
sufficient to generate the vapor for lighting the lamp, but as soon as
lighted the heat from the glowing mantle keeps the generator at the
required temperature for continuous supply of vapor.

When the generator is sufficiently heated by the generating torch,
the needle valve _N_ is opened by pulling the chain _P_. This allows
the gasoline vapor from the generating tube to escape at _G_ into the
induction tube _R_. As the vapor enters the induction tube at a high
velocity, it carries with it the atmospheric air in quantity sufficient
to render it completely combustible. The opening _G_ and the tube
together form a Bunsen burner. The lamp is so proportioned as to give a
mixture of gasoline vapor and air that will produce complete combustion
in the mantle _T_. The portion of the burner _Z_, through which the
gas enters the mantle, is a brass tip, filled with a fluted strip of
German silver, so arranged that the gas on entering the mantle will
be uniformly distributed and that the heat generated will render the
entire mantle uniformly brilliant.

One feature of the lamp that requires special attention is the opening
_G_, through which the vapor from the generator is discharged into the
induction tube. This is a very small opening and occasionally becomes
stopped or partly closed. When this occurs the lamp fails to receive
the necessary amount of gas, and the light is unsatisfactory. In this
lamp, the cleaning needle _Q_ is provided for removing the stoppage.
The needle is simply screwed into the opening and forces out the
obstruction; when it is withdrawn, the opening is left free. A more
convenient device for accomplishing the same purpose is described in
the portable lamp, Figs. 195 and 196.

=Portable Gasoline Lamps.=--The portable form of desk and reading lamps
for the use of gasoline is made in a great variety of styles. They
are sometimes constructed to feed by gravity, but by far the greater
number are operated by the pressure method. The portable lamp must be
a complete gas plant, with storage tank for the gasoline, pipe system
for conducting the gasoline to the lamp, generator and burner. To give
satisfactory results, the lamp must be capable of being lighted with
the least degree of trouble and operated with the least amount of care.
The immense number of lamps of this kind that are sold shows that
they meet all of these requirements and have proven satisfactory in
operation. Their greatest attractiveness is their capability of giving
a very large amount of light at relatively low cost.

Fig. 195 illustrates a portable gasoline lamp in which a convenient and
efficient form of generating mechanism is combined with an attractively
proportioned exterior. The lamp works on the principle of the
hollow-wire system, the base serving as a storage and pressure tank,
the frame of the lamp acting as the tube for supplying the lamp with
gasoline, and the canopy containing the generating mechanism.

[Illustration: FIG. 195.--Portable gasoline mantle lamp.]

The tank in the base is filled with gasoline at the opening _E_, which
is made air-tight by a screw-plug. The plug also contains an attachment
piece for the air pump, which furnishes the pressure to the gasoline.
The hollow standard reaches to the bottom of the tank and through it
the gasoline is forced to the point marked _A_, where the gasoline
enters the generating mechanism. This part of the lamp, which is
entirely concealed by the lamp canopy, is shown in detail in Fig. 196.
The reference letters in Fig. 195 apply to the same parts in the detail

The gasoline enters an asbestos-packed tube _F_ at the point _A_, and
after percolating through the tube, reaches the regulating valve at
the point _G_. The hand-wheel _B_ opens and closes the valve, and thus
controls the entrance of the gasoline to the generating tube _H_, where
it is converted into the vapor. The vapor now needs only the addition
of air to make it the desired gas for illuminating the mantle.

The vapor from the generating tube escapes at the small hole _K_,
located directly under the mixing chamber _M_. The supply of air is
received through the tube _C_, provided with a regulator, which
is readily accessible from the outside of the lamp. The mixture of
gasoline vapor and air is accomplished as in the other lamps described,
through the Bunsen tube _N_. In this case, the Bunsen tube is extended
and increased in size to produce a mixing chamber of considerable
volume. The mantle is attached to the tip _O_. The tip, like the one
already described, is made of German silver and constructed to produce
a flame that will entirely fill the mantle.

This lamp is provided with a special means of keeping the opening _K_
free from accumulations. The opening _K_, through which the gasoline
vapor escapes from the generator, is very small and a slight stoppage
will materially interfere with the flow of the vapor and thus impair
the illuminating effect of the light. A lever _D_ operates an eccentric
which engages the piece _P_, to which is attached a pin that readily
enters an opening _K_, when the lever is turned. Any accumulation which
may lodge in the opening is instantly removed and the needle returned
to its place by a turn of the lever _D_.

[Illustration: FIG. 196.--Sectional view of the generator for the
American hollow-wire gasoline lamp.]

=Central-generator Plants.=--The central-generator or tube system of
lighting with gasoline, differs from the other methods described,
in the manner of generating and distributing the supply of gas to
the lamps. In the hollow-wire system each lamp generates its own gas
supply. With the central-generator system the gas for all of the lamps
is generated and properly mixed with air in a central generator, and
the finished gas distributed through tubes to the different burners
and there burned in incandescent mantles. The gas as it leaves the
generator requires no further mixing with air and therefore the
burners are not of the Bunsen type.

Central-generator gas machines are made in a number of different forms
by different manufacturers, all of which are intended to perform the
same work but differ in the mechanism employed. The machines are simple
in construction and as in the hollow-wire system are capable of using
lower grades of gasoline than can be used with the cold-process plants.
The gas from a central generator may be used for all purposes for
which gasoline gas is employed, either for lighting or heating. One
difficulty in the use of the machine is the lack of flexibility when
required for only a few lamps or varying number of lights. Although
these plants are sometimes used for lighting and heating dwellings,
their use is limited, for the reason that variation of the number of
lights requires the generator to be regulated to suit the change in the
gas supply. The plants cannot be conveniently cut down to one light.
Their most general use is that of lighting churches, stores, halls,
auditoriums, etc., where a variable amount of light is not demanded.
Plants of this character are quite generally used for street lighting
and for other outside illumination.

An efficient and simple plant of the central-generator type is shown in
Fig. 197. The supply of gasoline is stored in a tank similar to that
used with the hollow-wire system and placed in any convenient location.
The gasoline is conducted to the generator _G_, through a hollow wire
marked _W_. The generator is inclosed in a sheet-iron box, which is
located at any convenient place in the building. From the generator the
gas is conducted through the tube to the lamps _L_.

In Fig. 198 is shown a diagram of the generator, cut through the middle
lengthwise, in which all of the working parts are shown in their
relative positions. The reference figures designate the same parts of
the generator in Figs. 197 and 198.

In the process of generation the tank is filled with gasoline and
pressure applied with the air pump. The tanks described in Fig. 189
might be used to advantage with this plant but the one shown in Fig.
197 is so constructed that the larger tank is used for storage of
gasoline. The gasoline is pumped directly into the smaller tank which
alone is kept under pressure. The pump _P_ is enclosed in the large
tank; at any time it is desired to replenish the supply of gasoline, it
is only necessary to open the valve _V_ and pump the necessary supply
into the small tank. This transfer may be done at any time without
danger from escaping gasoline vapor.

[Illustration: FIG. 197.--Diagram of central-generator tube system of
gasoline lighting.]

The process of generating the gas is best understood by reference to
Fig. 198, which shows the internal construction of the generator. The
liquid gasoline is admitted at the bottom through the small pipe _W_,
and then enters the space 4, where it is vaporized. The initial flow of
gas is generated by heating the generator with an alcohol flame from
the iron cup 1, which surrounds the generator. When the generator is
heated the gasoline admitted to the generator is immediately vaporized;
when, by turning the handle 6, the needle valve 5 opens a small
orifice through which the heated gasoline vapor escapes into the tube
7, above.

The blast of vapor issuing from the orifice carries with it air of
sufficient volume to render the gasoline vapor an explosive mixture
that when burned in the mantle will be reduced to CO₂ gas.

When the initial heating by the alcohol flame is exhausted, sufficient
gas has been generated so that part of it may be used as a sub-flame in
the gas burner 9, to keep the generator heated. The gas is conducted to
the burner from the main tube 11, through the pipe 12-14, as indicated
by the arrows. The burner 9 surrounds the generator and the size of
the flame is regulated by the valve 15, which is opened an amount
sufficient to admit the necessary gas to the burner.

To start the generator, the cup 1 is filled with alcohol and ignited.
The needle valve 2 is now opened by turning the hand-wheel 3, admitting
gasoline into the generator chamber 4, where the vaporization of the
gasoline takes place. The flame from the burning alcohol will heat the
generator in about a minute. When the generator is hot, the needle
valve 5 is opened slightly, by turning the lever 6, and the gasoline
vapor under high pressure blows into the tube 7. As the gasoline vapor
is blown into the tube 7, air is drawn in through the opening 8, as
indicated by the arrows. The generator is practically a large Bunsen
tube from which the mixture of gasoline vapor and air is conducted to
the burners by a connecting pipe.

[Illustration: FIG. 198.--Cross-section of the generator for the tube
system of gasoline lighting.]

Gas machines operated on this principle are made to accommodate a
definite number of lamps. After the lamps are lighted, the amount
of gas is regulated to suit the number in use. If at any time it is
desired to reduce the number of lamps in operation, the gas supply
must be regulated to suit the lights left burning.

As an illustration, suppose that a plant of ten lamps had been burning
and that it was desired to reduce the number to six; four of the
lamps are extinguished by turning the levers _C_, which control the
gas-cocks. The generator which had been supplying sufficient gas for
ten lights will continue to produce the same amount until the lever 6
is turned to reduce the supply of gasoline to the required amount for
six lamps. This is done by gradually closing the valve 5 until the
lamps again burn brightly.

In small plants the least number of lamps that will work satisfactorily
at one time is three. Automatic regulators are made for plants of
considerable size but do not satisfactorily control the gas when the
lamps are reduced below three in number. The gas from these plants may
readily be used in kitchen ranges, water heaters and other domestic
purposes. Individual plants for operating ranges in restaurants and
hotels are in common use. The plants are subject to minor derangements
that require correcting as they occur, but as soon as the mechanism and
characteristic properties of the plant are known, the correction of any
difficulty that may present itself is easily accomplished.

[Illustration: FIG. 199.--Gas lamp for use with the central-generator
or tube system of gasoline lighting.]

=Central-generator Gas Lamps.=--Fig. 199 shows the general construction
and arrangement of the parts of the inverted-mantle lamp used with the
central-generator system. In outward appearance the lamp is much like
any other inverted-mantle gas lamp, but in arrangement of parts it is
markedly different. The gas-cock _C_ is larger than that used with the
ordinary fixture, because the opening _O_ must carry a larger volume of
gas than that for supplying gas to lamps using the Bunsen tube. In the
use of lamps with the Bunsen tube, the gas from the mains is mixed with
approximately twenty times its volume of air; with a lamp like that of
Fig. 199, where the mixture has already been made in the generator, the
conducting tubes and the gas-cock must be relatively very large.

The screen _S_, which corresponds to the screen _S_ in Fig. 192, is
quite as necessary as in the other lamp. It not only assures a uniform
distribution of the gas in the tube but it prevents the mantle from
being broken when the burner is lighted. If this screen is punctured,
the explosion which takes place when the burner is lighted will be
sufficient to blow out the bottom of the mantle. The burner tip _T_ is
practically the same as that used with other mantle lamps.

=Boulevard Lamps.=--Gasoline lamps for outside illumination may be
constructed to operate with any of the systems described, but the
hollow-wire and the generator systems are most conveniently used,
because each post may be arranged as an independent plant. For
illuminating private grounds or public thoroughfares, lamps such as are
illustrated in Figs. 200 and 201 are very generally used.

The lamp shown in Fig. 200 is of the central generator type in which
the storage tank and generator mechanism are located in the base of the
post. These lamps are also sometimes constructed with a time attachment
in the base of the post, arranged with a clock mechanism so that the
light may be automatically extinguished at any desired time.

[Illustration: FIG. 200.--Boulevard lamp with generator in the base of
the lamp post.]

[Illustration: FIG. 201.--Boulevard lamp operated by the hollow-wire
method of lighting.]

In Fig. 201 the lamp is of the hollow-wire type and as in the case
of the other, the supply tank is in the base of the post. With this
system it would be possible to supply several lamps from a common
supply tank, provided the hollow wire was protected against damage. The
lamps arranged to work on either system, require the same amount of
attention and are subject to the same derangements as those for inside

=Burners for gasoline stoves= are made in a great variety of forms,
each having some special points of excellence that are used to
recommend the sale of the stove. The most essential feature of a
gasoline stove is the burner, since on its successful performance
will depend the satisfaction given by the stove. Many self-generating
burners have been devised which have met with a great deal of favor,
but the type of burner most widely used and the first to be devised
for the purpose is the generating burner similar in principle to the
generating gasoline lamp.

The burner is first heated from an outside source, in order to generate
sufficient gas to start the flame, after which the heat from the burner
will develop the gas supply. With gasoline stoves of this kind, the
supply tank is elevated, in order that the force of gravity may give
sufficient pressure to send the gasoline into the generator while the
flame is burning. In the hollow-wire system the same type of burner is
used, but the gasoline is forced into the burner by the pressure in the

[Illustration: FIG. 202.--Sectional view of the generator and burner of
a gasoline stove.]

In Fig. 202 is shown a sectional view of the burner as it appears in
the stove. The supply tank, or hollow wire from the pressure tank,
sends the gasoline into the tube _A_ at the bottom of the stove, to
which several burners may be attached. The tube _B_, through which
the gasoline percolates on its way to the generator, is filled with
moderately coarse sand, or other material that is intended to prevent
the gasoline from being forced out of the pipe by the pressure that
is developed in the generator. The pieces _C-C_ are perforated metal
plugs that prevent the escape of the particles of which _B_ is composed.

The generator is a brass casting _D-D_ which is firmly screwed to
the top of the tube _B_. A needle-valve _E_ governs the discharge of
the gasoline vapor at _G_, where the vapor enters the tube _H_, as
indicated at _K-K_. The gasoline vapor enters the open Bunsen tube
_H_, and with it is carried the air necessary to produce the required
gas for complete combustion. The piece _N_ is the generating cup in
which is burned the generating fluid--either gasoline or alcohol. The
gasoline from the pipe _A_ percolates through the material in _B_ and
flows into the generator. The needle-valve being closed, the space
_D-D_ fills with gasoline.

To light the burner, the hand-wheel _J_ is turned, opening the
needle-valve a sufficient length of time to allow the gasoline to fill
the cup _N_ with fuel for generating the initial volume of vapor. A
still better way is to fill the cup with alcohol, because the burning
alcohol does not fill the air with smoke and odors, as in the case of
gasoline, when used for generating purposes. The generating material
having been ignited and burned out, the generator is hot and filled
with vapor. The heated generator vaporizes a portion of the contained
gasoline and forms sufficient pressure to force the remaining gasoline
back through _B_ into the supply tank. The material of the tube
_B_ permits only a slow movement of the gasoline and prevents the
possibility of surging in the generator.

The initial supply of vapor being generated, the needle-valve may be
opened and the gas lighted above the burner _I-I_, where it should burn
in little jets at each opening with the characteristic Bunsen flame. It
sometimes happens that the generator is not heated sufficiently, by the
generating flame, to vaporize the necessary gasoline for starting the
burner; in this case liquid gasoline will be forced from the opening
_G_, and the burner will flare up intermittently in a red smoky flame.
When this occurs the burners must be regenerated.

=Gasoline Sad Irons.=--The use of gaseous or liquid fuel is always
attended by an element of danger, because of the possibility of
accidental explosion. The use of gasoline, the most highly volatile
of all liquid fuels, has, however, come to be very generally used as
a source of heat for domestic purposes. The danger of accident in
the use of gasoline as a fuel for heating sad irons is largely due to
ignorance of the involved mechanism or carelessness in manipulation.
A knowledge of the principle included in their operation, together
with an observance of the possible cause of accident, will reduce the
element of danger to a negligible quantity.

The use of gasoline sad irons has come into favor because of their
convenience and economy in operation. These irons, in common with the
use of gasoline in its other applications of heating and lighting, are
made in a great many forms but the principle of operation is confined
to two types.

[Illustration: FIG. 203.--Gasoline flat-iron operated by a heated fuel

[Illustration: FIG. 204.--Gasoline flat-iron showing the position of
the cover while initial charge of gas is being generated.]

_First_, those in which the gasoline is forced into the generator by
the vapor pressure, from the heated supply tank; and _second_ those in
which the pressure is caused by pumping air into the supply tank after
the manner of the hollow-wire system of lighting.

The first type of iron is illustrated in Fig. 203. The same iron is
shown in Fig. 204, with the top in position for generating vapor
pressure necessary to start the burner. The body of the iron A is a
hollow casting, designed to receive the generator and burner in such
position that the bottom portion of the iron may be uniformly heated.
The generator and burner are shown in detail in Fig. 205, in which a
sectional view is given of the parts, cut across lengthwise of the iron.

In starting the burner for use, the tank is first filled--not quite
full--of strained gasoline. The precaution of straining the gasoline
should be taken, to prevent putting into the tank anything that will
possibly choke the needle-valve. Alcohol is used for generating the
vapor supply, because the flame does not black the iron and fill the
room with smoke as in the case when gasoline is used for the purpose.
When the alcohol is ignited, the cover is placed in position as shown
in Fig. 204, so that the flame may heat not only the generator but
also the tank. The object of heating the tank is that the heated
gasoline may furnish pressure with which to force the gasoline into the
generator. When the alcohol used for generating is almost burned out,
the valve _F_ is slightly opened and the burner lighted.

[Illustration: FIG. 205.--Sectional view of gasoline flat-iron
generator and burner.]

As shown in Fig. 205, the generator _G_ is a brass tube, inclosing the
valve-stem _G_, which terminates in the needle-valve _V_. This valve
regulates the supply of gas admitted to the burner and is operated by
the hand-wheel _F_. When the gasoline in the tank has been heated the
necessary amount, the vapor in _G_ is allowed to escape through the
valve _V_. The vapor is discharged into the Bunsen tube, and with it
the air is carried in through the openings _E_, from both sides of the
iron. The burner is a brass tube, slotted as shown at _H_, through
which the gas escapes, forming a short flame of large area close to the
part of the iron to be heated. The size of the flame is regulated by
the hand-wheel _F_.

The tank is entirely closed, the plug _P_ being provided with a
lead washer to insure a tight joint. The plug is further provided
with a soft metal center which acts as a “safety-plug” in case of
overheating. Should the iron at any time become too hot, the soft metal
center will melt and the released pressure in the tank will put out
the burner flame. The soft metal center may be renewed with a drop
of solder. In case the safety-plug at any time is melted, the hot
gasoline will spurt from the opening and immediately vaporize. This of
course would, in a short time, produce an explosive atmosphere which
if ignited would be dangerous. In case of accident the iron should be
carried to the open air and the flame smothered with a cloth.

=Alcohol Sad Irons.=--Irons of the same style are also made in which
alcohol is used as a fuel. The alcohol irons differ in construction
from those using gasoline only in the amount of air that is mixed with
the vapor. In general appearance the two styles look very much alike,
but in the alcohol iron one of the intakes _E_ is entirely closed and
the other opening is partially closed.

[Illustration: FIG. 206.--Gasoline flat-iron operated by an
air-pressure fuel tank.]

The operation of these irons is identical to those using gasoline, but
they are preferred by those who fear the use of that fuel. In reality
there is little difference in the danger attending the use of the two
liquids. It is only fair to say, however, that the use of any highly
volatile fuel is attended with some danger when used carelessly, but
with a reasonable amount of care and a knowledge of the mechanism of
the machine in use the danger is of minor consequence.

In Fig. 206 is illustrated another style of gasoline sad iron, the
working principle of which is the same as those already described but
the supply tank is not heated to give pressure to the gasoline in the
tank. In this iron the tank is located at one side of the iron and
pressure is applied with an air pump as in the hollow-wire system of
lighting. The burner is generated after the manner of the others and
operated in exactly the same manner. The chief difference is that the
possibility of excessive pressure through overheating is eliminated.

=Alcohol Table Stoves.=--In the United States the use of alcohol as a
fuel has never been extensively employed because of the duty imposed
on its manufacture by the Federal Government. In 1896 this duty was
removed from denatured alcohol and the cost was sufficiently reduced to
permit a great extension in its use as a fuel.

Denatured alcohol is any alcohol to which has been added any of the
list of prescribed volatile fluids that will render the alcohol unfit
for use in beverages and not materially change its heating value.
Denatured alcohol is sold at a price that will permit its use in small
flat-irons, table stoves and other forms of burners where small amounts
of heat are generated for convenience. At the price of denatured
alcohol as generally sold, it cannot compete with gasoline and kerosene
as a fuel.

In Fig. 207 is shown a convenient and inexpensive form of table stove,
in which the vapor of alcohol is burned in practically the same manner
as the vapor of gasoline in the burners already described. The supply
of alcohol is stored in a tank _A_, and fed by gravity to the burner
_B_, the flame from which resembles that of the ordinary gasoline

The generator _G_ with the other essential parts are shown in detail in
Fig. 208. The reference letters indicate the same parts in the detail
drawing as in Fig. 207.

[Illustration: FIG. 207.--Alcohol vapor stove.]

[Illustration: FIG. 208.--Sectional view of the generator and burner of
the alcohol vapor stove.]

The alcohol flows from the supply tank through the pipe _C_ to the
generator _G_, which is a brass tube filled with copper wires. The
vapor for starting the burner is generated by opening the valve _V_
and allowing a small amount of alcohol to flow through the orifice _C_
into the pan _P_ directly below the generator. The valve is then closed
and the alcohol ignited. When the generating flame has burned out, the
valve _V_ is again opened and the vapor which has generated in the tube
escapes at the orifice _C_ and enters the Bunsen tube _T_, (Fig. 207)
carrying with it the proper amount of air to produce the Bunsen flame
at each of the holes of the burner.

As in the case of the gasoline burners the orifice _C_ sometimes
becomes clogged and it is necessary to insert a small wire to clear
the opening. With the stove is provided a tool for this purpose. With
stoves of this kind, the supply tank must not be tightly closed,
because any pressure in the tank would cause it to become dangerous.
The alcohol is fed to the generator entirely by gravity. The stopper of
the tank contains a small hole at the top which should be kept open to
avoid the generation of pressure should the tank become accidentally

Stoves of this kind may be conveniently used for a great variety of
household purposes, and when intelligently handled are relatively free
from danger.

=Danger from Gaseous and Liquid Fuels.=--All combustible gases or
vapors, when mixed within definite amounts, are explosive. The violence
of the explosion will be in proportion to the volumes of the gas and
the condition of confinement.

When gasoline or other volatile fuel is vaporized in a closed room,
there is danger of an explosion, should the mixture of the vapor and
air reach explosive proportions. It is dangerous to enter a room with
a lighted match or open-flame lamp, where gaseous odor is markedly
noticeable. In case of danger of this kind the windows and doors should
be immediately opened to produce the most rapid ventilation.

In the act of igniting the flame in a gas or vapor stove, the lighter
should be made ready before the gas is turned on. Explosions in gas and
vapor stoves are usually due to carelessness in igniting the fuel. It
should be kept constantly in mind that, if a combustible gas is allowed
to escape and mix with air in any space and then ignited, an explosion
of more or less violence is sure to occur.

Gasoline and kerosene are lighter than water and will float on its
surface. The flames from these oils are aggravated when water is used
in attempting to extinguish them. The burning oil floating on the
surface of the water increases the burning surface.

Burning oil must be either removed to a place where danger will not
result or the flames must be smothered. In case of a small blaze,
the fire may be extinguished with a cloth, preferably of wool, or if
circumstances will permit, with ashes sand or earth.

Alcohol dissolves in water and may, therefore, be diluted to a point
where it will no longer burn.


Acetylene is a gas that is generated when water is absorbed by calcium
carbide, after the manner in which carbonic acid gas is evolved when
lime slakes with water, but with the liberation of a larger amount of
the combustible gas.

Calcium carbide is a product resulting from the union of lime and
coke, fused in an electric furnace to form a grayish-brown mass. It is
brittle and more or less crystalline in structure and looks much like
stone. It will not burn except when heated with oxygen. A cubic foot of
the crushed calcium carbide weighs 160 pounds.

Calcium carbide--or carbide as it is ordinarily termed--may be
preserved for any length of time if kept sealed from the air, but the
ordinary moisture of the atmosphere gradually slakes it and after
exposure for a considerable time it changes into slaked lime. The
carbide itself has no odor, but in the air it is always attended by
the penetrating odor of acetylene, because of the gas liberated by the
moisture absorbed from the air.

If protected from moisture, calcium carbide cannot take fire, being
like lime in this respect; it is therefore a safe substance to store.
It is transported under the same classification as hardware, and will
keep indefinitely if properly sealed.

A pound of pure carbide yields 5-1/2 cubic feet of acetylene, but in
commercial form, as rated by the National Board of Fire Underwriters,
lump carbide is estimated at 4-1/2 cubic feet per pound. In the
generation of acetylene, exact weights of carbide and water always
enter into combination, _i.e._, 64 parts of carbide to 34 parts of
water, and a definite amount of heat is evolved for each part of
carbide consumed.

Uncontrolled, the gas burns with a bright but not brilliant flame
and with a great deal of smoke, but when used in a burner suited for
its combustion it burns with a clear brilliant flame of a quality
approaching sunlight. While carbide is not explosive nor inflammable,
it may, if it finds access to water, create a pressure such as to burst
its container, and it is not impossible that heat might be generated
sufficient to ignite the gas under such conditions. That such condition
would often occur is not at all probable. When water is sprinkled upon
carbide, in quantity such that it will all be taken up, the resultant
slaked lime is left dry and dusty, and occupies more space than
the original carbide. When more than enough water is employed, the
remaining mixture of lime and water is whitewash.

Chemically considered, acetylene is C₂H₂; it is composed of carbon and
hydrogen and belongs to a class of compounds known as hydrocarbons,
represented in nature by petroleum, natural gas, etc. It is composed of
92.3 per cent. carbon and 7.7 per cent. of hydrogen, both combustible
gases. It is a non-poisonous, colorless gas, with a persistent and
penetrating odor. Its presence in the air, to the extent of 1 part in
1000 is distinctly perceptible. When burning brightly in a jet, there
is no perceptible odor. When completely burned it requires for its
combustion 2-1/2 times its volume of oxygen.

All combustible gases, when mixed with air and ignited, produce more
or less violent explosions. Acetylene is no exception to the rule, and
when allowed to escape into any enclosed space it will quickly produce
a violently explosive mixture, so that it is always dangerous to enter
a room or basement with a lamp or flame of any kind where the odor
of gas is perceptible. This is quite true with a combustible gas of
any kind, but with acetylene all mixtures from 3 to 30 per cent. are
capable of being exploded with greater or less violence.

The kindling point of acetylene is lower than coal gas or gasoline
gas. To ignite either of the latter gases, a flame is necessary to
start the combustion, but a spark or a glowing cigar is sufficient to
ignite acetylene. It should therefore be borne in mind that acetylene
is not only explosive when mixed with air but that it is very easy to
ignite. Under ordinary pressures pure acetylene is not explosive, but
at pressure above 15 pounds to the square inch explosions sometimes
occur where proper precautions are not observed. At all pressures such
as are required for household purposes acetylene is as safe for use as
any other gas.

Although acetylene is in danger of exploding when under pressure, it is
perfectly safe, when the proper conditions are observed, in tanks for a
great many kinds of portable lights.

Where acetylene is used in portable tanks under pressure, advantage
is taken of its solubility in acetone. This is a product of the
distillation of wood which possesses the property of absorbing
acetylene to a remarkable degree. In addition to this property is
the more important one of rendering the acetylene non-explosive when
under pressure. The tanks for its storage are filled with asbestos or
other absorbent material that is saturated with acetone. The acetylene
is then forced into the tanks under pressure and is absorbed by the
acetone. The safety of this means of storage lies in the degree of
perfection to which the tanks are filled with the absorbent material.
There must be no space anywhere in the tank where undissolved acetylene
can exist. Its freedom from danger under such conditions has been
thoroughly demonstrated in its use for railroad and automobile lamps.

The use of acetylene as a fuel for cooking and for the various other
purposes of domestic use is successfully accomplished in burners that
give the blue flame desired for such purposes. Complete cooking ranges
and various other heating and cooking devices are regularly sold
by dealers in heating appliances, while water-heaters, hot-plates,
chafing-dish heaters, etc., are as much a possibility as with any other
of gaseous fuel and in as reasonably an inexpensive way.

Coal gas, containing as it does sufficient carbon monoxide to render it
poisonous, will cause death when inhaled for any length of time, but
acetylene under the same conditions will have no deleterious effect.

=Types of Acetylene Generators.=--There are two general methods of
generating acetylene for domestic illuminating and heating purposes:
that of adding carbide to water, and that in which the water is mixed
with carbide. The two types are illustrated in the diagrams shown
in Figs. 209 and 210. The first method, that in which the carbide
is dropped into water, is shown in Fig. 209. The tank _A_ is the
generator and _B_ is the receiver or gas-holder. The tank _A_ holds a
considerable quantity of water and is provided with a container _C_
for holding the supply of carbide. The tank _A_ is connected with the
gas-holders by a pipe which extends above the water line in the tank
_B_, where the gas is allowed to collect in the gas-holder _G_. A
charge of carbide, sufficient to fill the holder with gas, is pushed
into the tank _A_ by raising the lever _H_. Immediately the water
begins to combine with the carbide and the bubbles of gas pass up
through the water and are conducted into the tank _B_. The holder _G_
is lifted by the gas and its weight furnishes the pressure necessary
to force the gas into the pipes, which conduct it to the burners. If
this machine were provided with the proper mechanism to feed into
the generator a supply of carbide whenever the gas in the holder is
exhausted, the machine would represent the modern “carbide to water”

[Illustration: FIG. 209.--Diagram of a carbide-to-water acetylene-gas

[Illustration: FIG. 210.--Diagram of a water-to-carbide acetylene-gas

The “water to carbide” generator is shown diagrammatically in Fig. 210.
As in the other figure, _A_ is the generator and _B_ is the gas-holder.
A supply of carbide _S_ is placed in the generator and water from a
tank _C_ is allowed to drip or spray onto the carbide. The gas collects
in the gas-holder as before. This apparatus represents in principle the
parts of a machine for generating acetylene by this process. The actual
machines are arranged to perform the functions necessary to make the
machines automatic in their action.

Whatever the type of the machine, the object is to keep in the holders
a sufficient amount of gas with which to supply the demand made on
the plant. Machines representing each of the types described are to
be obtained, but the greater number of those manufactured are of the
“carbide to water” form.

In the formative period of acetylene generators many accidents of
serious consequence resulted from imperfect mechanism. Imperfections
have been gradually eliminated until the machines which have survived
are efficient in action and mechanically free from dangerous

The qualities demanded of a good generator are: There must be no
possibility of an explosive mixture in any of the parts; it must insure
a cool generation of gas; it must be well-constructed and simple to
operate; it should create no pressure above a few ounces; it should be
provided with an indicator to show how low the charge of carbide has
become in order that it may be recharged in due season, and it must use
up the carbide completely.

Because of the fact that the greater number of acetylene-gas machines
of today are of the “carbide to water” type, in the description to
follow that type of machine is used. They are generally made in two
parts, one part containing the generating apparatus and the other
acting as gasometer (gas-holder), but some machines are made in which
one cell contains both the generator and gasometer.

In Fig. 211 is shown a two-part, gravity-fed machine, in which all of
the internal working parts are exposed to view. The tank (_a_), as in
the diagram, is the generator and the tank (_b_) contains the gasometer
marked _G_. Each tank possesses a number of appliances which are
necessary to make the machine automatic in its action. The part _C_ of
the generator contains the supply of carbide, broken into small pieces,
a portion of which is dropped into the water whenever additional gas is
required. The feed mechanism _F_ is controlled by the gasometer bell
_G_, which is buoyed up by the gas it contains. When the supply of gas
becomes low, the descending bell carries with it the end of the lever
_F_, which is attached to the feed valve; this motion raises the feed
valve and allows some of the carbide to fall into the water. The gas
that is immediately generated passes into the gasometer through the
pipe _P_, and as the bell is raised by the accumulating gas the valve
_V_ is closed.

The gas as it enters the gasometer passes through a hollow device _W_,
that looks like an inverted T, the lower edge of which is tooth-shaped
and extends below the surface of the water. The gas, in passing this
irregular surface, is broken up and comes through the water in little
bubbles, in order that it may be washed clean of dust. This device also
prevents the return of the gas to the generator tank during the process
of charging.

[Illustration: FIG. 211.--Sectional view of the Colt acetylene-gas

The gas escapes from the bell through the pipe _S_ to the filter _D_,
where any dust that may have escaped the washing process is removed
by a felt filter. It finally leaves the machine by the pipe _L_, at
which point it enters the system through which it is conveyed to the
different lighting fixtures.

It will be noticed that the tank (_b_) is divided into two
compartments, the upper portion containing the water in which the
gasometer floats. The lower compartment is also partly filled with
water which acts as a safety valve to prevent any escape of gas into
the room in which the generator is located. The lower end of the pipes
_P_ and _S_ are immersed in the water at the bottom chamber of the
tank, from which the gas could escape in case too much is generated and
finally exit through the vent pipe _U_ to the outside air.

The float _A_ in the tank (_a_) is a safety device that prevents the
introduction of carbide unless the tank contains a full supply of
water. The float is a hollow metal cylinder connected by a rod to a
hinged cup under the bottom opening of the carbide holder. When the
water is withdrawn from the generator, the float falls and the cup
shuts off the carbide outlet.

[Illustration: FIG. 212.--Sectional view of a house equipped with
acetylene lights and domestic heating apparatus.]

The accumulation of lime, from the disintegrated carbide, requires
occasional removal from the tank (_a_); the valve _K_ is provided
for this purpose. The lever _S_ is used to stir up the lime which is
deposited on the bottom of the tank, that it may be carried out with
the discharged water.

Machines of this kind that are safeguarded against leakage of gas or
the possibility of accumulated pressure are practically free from
danger in the use of acetylene. The accidental leakage of gas from
defective pipes and fixtures produce only the element of risk that
is assumed with the use of any other form of gas for illuminating

Acetylene is distributed through the house in pipes in the same manner
as for ordinary illuminating gas. The sizes of the pipes to suit the
varying conditions of use are regulated by rules provided by the
National Board of Fire Underwriters. These rules state definitely the
sizes of pipes required for machines of different capacities. Rules of
this kind and others that specify all matters relating to the use of
acetylene may be obtained from any fire insurance agent.

The general plan of piping is shown in Fig. 212. The generator _G_ is
in this case a “water to carbide” machine and is shown connected to the
kitchen range, as well as the pipe system which may be traced to the
lamps in the different rooms, to the porch lights and to the boulevard
lamp in front of the building.

[Illustration: FIG. 213.--Acetylene gas burner.]

[Illustration: FIG. 214.--Electric igniter for acetylene gas burners.]

[Illustration: FIG. 215.--Electric igniter for acetylene gas burners.]

The type of burner used in acetylene lamps is shown in Fig. 213. The
gas issues from two openings to form the jet as it appears in the
engraving. These burners are made in sizes to consume 1/4, 1/2, 3/4,
and 1 foot per hour depending on the amount of light demanded.

=Gas Lighters.=--The acetylene gas jets are lighted ordinarily with a
match or taper but electric igniters are often used for that purpose.
Electric lighters for acetylene lamps are practically the same as those
used with ordinary gas lamps but they must be adapted to the type of
burner on which they are used. Electric igniters that are intended
to be used with lamps placed in inaccessible places are different
in construction from those within reach. In Figs. 214 and 215 are
illustrated two forms of igniters that are intended to be used on
bracket or pendent lamps. They differ in mechanical construction to
suit two different conditions. Fig. 214 is an igniter in which is also
included the gas-cock. The gas is lighted by pulling a cord or chain
attached to the lever _L_. The movement of this lever turns on the gas
and at the same time brings the piece _C_ in contact with the wire
_A_ to complete an electric circuit. As the contact between these two
pieces is broken, a spark is formed that ignites the gas escaping from
the burner at _B_. On releasing the lever a spring returns the piece
_C_ to its original position. The light is extinguished by a second
pull of the lever.

Fig. 215 illustrates a style of igniter which may be attached to an
ordinary gas-cock. It is attached to the stem of the burner by a clamp
_D_. The gas is turned on by the usual gas-cock and by pulling the
chain at the left the jet is lighted. In pulling the chain the arm _A_
is raised and carries with it the arm _B_. When the arms _A_ and _B_
touch, an electric circuit is formed with a battery and spark coil.
When the desired position of the arms is reached, the points separate
to form an electric flash which lights the gas.

[Illustration: FIG. 216.--Diagram of electric igniters attached to gas

Fig. 216 illustrates in _A_ the method of installing electric igniters
like those described. A battery _B_ and a spark coil _S_ are joined in
circuit as shown. The gas pipe acts as one of the wires of the circuit.
A battery of four dry cells is commonly used for the purpose. The
spark coil is a simple coil of wire wound on a heavy iron core, which
serves to intensify the spark when the circuit is broken. In using
the igniter, it is only necessary to see that the cells are joined in
series with the coil and attached to the insulated part of the igniter.
As already explained the action of the igniter is to close the circuit
and immediately break the contact at a point where the spark will
ignite the gas. On being released the igniter returns to its original

In the fixture shown at _C_ is an igniter such as is used in places
that cannot be conveniently reached. To light the jet, the circuit is
completed by turning the switch at _W_. As soon as the gas is lighted
the switch is again turned to break the igniter-circuit. In this device
the current passes through a magnet coil in the igniter which acts to
open and close the circuit with the same effect as in the others.

=Acetylene Stoves.=--Stoves in which acetylene is used as a fuel
are quite similar in construction to those which burn coal gas. The
principle of operation is that of mixing the acetylene with air in
proper proportion so as to produce complete combustion when burned.



The adaptability of electricity to household use for lighting, heating
and the generation of power has brought into use a host of mechanical
devices that have found a permanent place in every community where
electricity may be obtained at a reasonable rate, or where it can be
generated to advantage in small plants.

Because of its cleanliness and convenience, electricity is used
in preference to other forms of lighting, even though its cost is
relatively high. Electric power for household purposes is constantly
finding new applications and will continue to increase in favor because
its use as compared with hand power is remarkably inexpensive. Small
motors adapted to most of the ordinary household uses are made in
convenient sizes and sold at prices that are conducive to their greater
use. Human energy is far too precious to be expended in household
drudgery where mechanical power can be used in its place and often to
greater advantage.

Electric heating devices compete favorably with many of the established
forms of household heating appliances, the electric flat-iron being a
notable example. In all applications where small amounts of heat are
required for short periods of time, electricity is used at a cost that
permits its use, in competition with other forms of heating.

The remarkable advance that has taken place in electric transmission
in the past few years tends to an enormous increase in its use. The
constant increase in its use for lighting, heating and power purposes
is due in a great measure to the development of efficient electric
generating plants from which this energy may be obtained at the least
cost. In those communities where hydro-electric generation is possible
its field of application is almost without end.

=Incandescent Electric Lamps.=--Anything made in the form of an
illuminating device, in which the lighting element is rendered
incandescent by electricity, may properly be called an incandescent
lamp, whether the medium is incandescent gas as in the Moore lamp, an
incandescent vapor as the Cooper Hewitt mercury-vapor lamp, or the
incandescent filament of carbon or metal such as is universally used
for lighting.

From the year 1879, when Mr. Edison announced the perfection of the
incandescent electric lamp, until 1903, when for a short period
tantalum lamps were used, very little improvement had been made in
the carbon-filament lamp. Immediately following the introduction
of the tantalum lamp came the tungsten lamp, which because of its
wonderfully increased capability for producing light has extended
artificial illumination to a degree almost beyond comprehension. The
influence of the tungsten lamp has induced a new era of illumination
that has affected the entire civilized world. The development of the
high-efficiency incandescent lamp has brought about a revolution in
electric lighting. Its use is universal and its application is made in
every form of electric illumination.

Regardless of the immense number of tungsten lamps in use, the
carbon-filament lamp is still employed in great numbers and will
probably continue in use for a long time to come. In places where
lamps are required for occasional use and for short intervals of
time, the carbon filament still finds efficient use. In one form of
manufacture the carbon filament is subjected to a metalizing process
that materially increases its efficiency. This form, known commercially
as the GEM lamp, fills an important place in electric lighting.

Of the rare-metal filament lamps, those using tungsten and tantalum are
in general use, but the tungsten lamps give results so much superior
in point of economy in current consumed that the future filament lamps
will beyond doubt be of that type unless some other material is found
that will give better results.

The filaments of the first tungsten lamps were very fragile and were
so easily broken that their use was limited, but in a very short time
methods were found for producing filaments capable of withstanding
general usage and having an average life of 1000 hours of service.
These lamps give an efficiency of 1.1 to 1.25 watts per candlepower
of light, as will be later more fully explained. This, as compared
with the carbon-filament lamps which average 3.1 to 4.5 watts per
candlepower, gives a remarkable advantage to the former. The tungsten
lamp has a useful life that for cost of light is practically one-third
that of the carbon-filament lamp.

The metal tungsten, from which the lamp filament is made, was
discovered in 1871. It is not found in the metallic state but occurs as
tungstate of iron and manganese and as calcium tungstate. Up to 1906 it
was known only in laboratories and on account of its rarity the price
was very high. As greater bodies of ore were found and the process
of extraction became better known, the price soon dropped to a point
permitting its use for lamp filaments in a commercial scale.

Pure tungsten is hard enough to scratch glass. Its fusing point is
higher than any other known metal; under ordinary conditions it is
almost impossible to melt it and this property gives its value as
an incandescent filament. One of the laws that affect the lighting
properties of incandescent lamps is: “the higher the temperature of the
glowing filament, the greater will be the amount of light furnished for
a given amount of current consumed.” The high melting point permits the
tungsten filament to be used at a higher temperature than any other
known material. Tungsten is not ductile, and in ordinary form cannot
be drawn into wire. Because of this fact, the filaments of the first
lamps were made by the “paste” process, which consisted of mixing the
powdered metal with a binding material, in the form of gums, until the
mass acquired a consistency in which it might be squirted through a
minute orifice in a diamond dye. The resulting thread was dried, after
which it was heated, and finally placed in an atmosphere of gases which
attacked the binding material without affecting the metal. When heated
by electricity in this condition, the particles of metal fused together
to form a filament of tungsten. While the “paste” filaments were never
satisfactory in general use, their efficiency as a light-producing
agent inspired a greater diligence in the search for a more durable

Although tungsten in ordinary condition is not at all ductile, methods
were soon found for making tungsten wire and the wire-filament lamps
are now those of general use. One process of producing the drawn wire
is that of filling a molten mass of a ductile metal with powdered
tungsten after which wire is drawn from the mixture in the usual way.
The enclosing metal is then removed by chemical means or volatilized by

Of the difficulties encountered in the use of metal-filament lamps
that of the low resistance offered by the wire was overcome by using
filaments very small in cross-section and of as great length as could
be conveniently handled. The long tungsten filament requires a method
of support very different from the carbon lamp. The characteristic form
of tungsten lamps is shown in Fig. 217, in which the various parts of
the lamp are named.

[Illustration: FIG. 217.--An Edison Mazda lamp and its parts.]

The filament of an incandescent lamp is heated because of the current
which passes through it. The electric pressure furnished by the
voltage, forces current through the filament in as great an amount as
the resistance will permit. A 16-candlepower carbon lamp attached to a
110-volt circuit requires practically 1/2 ampere of current to render
the filament incandescent; the filament resistance must, therefore,
allow the passage of 1/2 ampere. With a given size of filament,
its length must be such as will produce the desired resistance. A
greater length of this filament would give more resistance and a
correspondingly less amount of current would give a dim light because
of its lower temperature. Likewise, a shorter filament would allow more
current to pass and a brighter light would result. When the size and
length of filament is once found that will permit the right amount of
current to pass, if the voltage is kept constant, the filaments will
always burn with the same brightness. This is in accordance with Ohm’s
law which as stated in a formula is

    _E_ = _RC_

that is _E_, the electromotive force in volts, is always equal to the
product of the resistance _R_, in ohms, and the current _C_, in amperes.

In the incandescent lamp, if the electromotive force is 110 volts and
the current is 1/2 ampere, the resistance will be 220 ohms and as
expressed by the law

    110 = 220 × 0.5

From this it is seen that any change in the voltage will produce
a corresponding change in the current to keep an equality in the
equation. If the voltage increases, the current also increases and
the lamp burns brighter. Should the voltage decrease the current will
decrease and the lamp will burn dim. This dimming effect is noticeable
in any lighting system whenever there occurs a change in voltage.

The quantity of electricity used up in such a lamp is expressed in
watts, which is the product of the volts and amperes of the circuit. In
the lamp described, the product of the voltage (110) by the amount of
passing current (1/2 ampere) is 55 watts. With the above conditions the
16 candlepower of light will require 3.43 watts in the production of
each candlepower. The best performance of carbon-filament lamps give a
candlepower for each 3.1 watts of energy.

The filament of the tungsten lamp must offer a resistance sufficient to
prevent only enough current to pass as will raise its temperature to
a point giving the greatest permissible amount of light, and yet not
destroy the wire. The high fusing point and the low specific heat of
tungsten permits the filament to be heated to a higher temperature than
the carbon filament and with a less amount of electric energy. These
are the properties that give to the tungsten lamp its value over the
carbon lamp.

The exact advantage of the tungsten lamp has been investigated with
great care and its behavior under general working conditions is
definitely known. In light-giving properties where the carbon-filament
lamp requires 3.1 watts to produce a candlepower of light, in the
tungsten filament only 1.1 watts are necessary to cause the same
effect. The tungsten lamp therefore gives almost three times as
much light as the carbon lamp for the same energy expended. The
manufacturers aim to make lamps that give the greatest efficiency
for a definite number of hours of service. It has been agreed that
1000 working hours shall be the life of the lamps and in that period
the filament should give its greatest amount of light for the energy

=The Mazda Lamp.=--The trade name for the lamp giving the greatest
efficiency is Mazda. The term is taken as a symbol of efficiency
in electric incandescent lighting. At present the Mazda is the
tungsten-filament lamp, but should there be found some other more
efficient means of lighting, which can take its place to greater
advantage, that will become the Mazda lamp.

=Candlepower.=--The incandescent lamps are usually rated in
light-giving properties by their value in _horizontal_ candlepower.
This represents the mean value of the light of the lamp which comes
from a horizontal plane passing through the center of illumination
and perpendicular to the long axis of the lamp. Candlepower in this
connection originally referred to the English standard candle which is
made of spermaceti. The standard candle is 0.9 inch in diameter at the
base, 0.8 inch in diameter at the top and 10 inches long. It burns 120
grains of spermaceti and wick per hour. This candle is not satisfactory
as a standard because of the variable conditions that must surround its
use. The American or International standard is equal to 1.11 Hefner
candles. The Hefner candle (which is the standard in continental
Europe and South American countries) is produced by a lamp burning
amylacetate. This lamp consists of a reservoir and wick of standard
dimensions which gives a constant quantity of light. The light from
this lamp has proven much more satisfactory as a means of measurement
of light than the English standard and therefore its use has been very
generally adopted.

The light given out by an incandescent lamp is not the same in all
directions. In making comparisons it is necessary to define the
position from which the light of the lamps is taken. The _horizontal
candlepower_ affords a fairly exact means of comparing lamps which
have the same shape of filament, but for different kinds of lamps
it does not give a true comparison. The _spherical candlepower_
is used to compare lamps of different construction as this gives
the mean value at all points of a sphere surrounding the lamp. The
candlepower is measured at various positions about the lamp with the
use of a photometer, and the mean of these values is taken as the mean
_spherical candlepower_.

At their best, carbon-filament lamps require in electricity 3.1
w.p.c. (watts per candlepower). As the lamp grows old the number of
watts per candle power increases, until in very old lamps the amount
of electricity used to produce a given amount of light may become
excessively large. According to a bulletin issued by the Illinois
Engineering Experiment Station on the efficiency of carbon-filament
incandescent lamps, the amount of electrical energy per candlepower
varied from 3.1 w.p.c., when new, to 4.2 w.p.c., after burning 800

A common practice in the use of carbon-filament lamps is to consider
that the period of useful life ends at a point where the amount of
electricity, per candlepower, reaches 20 per cent. in excess of the
original amount. This point (sometimes termed the smashing point) would
be reached after 800 working hours, according to the Illinois Station,
and at about 1000 hours as stated by the bulletins of the General
Electric Co. If a carbon-filament lamp burns for an average period of 3
hours a day for a year, it ought to be replaced.

The Edison screw base as shown in Fig. 217 is now generally used in
all makes of incandescent lamps for attaching the lamp to the socket.
When screwed into place this base forms in the socket the connections
with the supply wires, to produce a circuit through the lamp. One end
of the filament is attached to the brass cap contact; the opposite
end connects with the brass screw shell of the base. When the current
is turned on, the contact made in the switch is such as to form a
complete circuit between the supply wires; the voltage sending a
constant current through the lamp produces a steady incandescence of
the filament.

In Fig. 218 is shown a carbon-filament lamp attached to an ordinary
socket. The lamp base and socket are shown in section to expose all of
the parts that comprise the mechanism. The insulated wires of the lamp
cord enter the top of the socket and the ends attach to the binding
screws _A_ and _B_, which are insulated from each other and form the
brass shell which encases the socket. The lamp base is shown screwed
into the socket, the brass cap contact _F_ making connection at _G_;
the screw shell joins the socket at _D_. To the key _S_ is attached a
brass rod _R_, on which is fastened _E_, the contact-maker. The rod
_R_ passes through a supportary frame which is secured to the lamp
socket at _G_. As shown in the figures the piece _E_ makes contact with
a brass spring attached to _A_, and this completes a circuit through
the filament. The brass cap contact of the lamp base makes connection
at one end of the filament _H_, the other end of the filament _K_ is
attached to the brass screw shell of the base, which in turn connects
with the screw shell of the socket and this shell is connected with the
piece containing the binding screw _B_ by the rod _C_ to complete the
circuit. When the key _S_ turns, the contact above _E_ is broken and
the lamp ceases to burn.

[Illustration: FIG. 218.--Section of a lamp base and socket.]

Fig. 118 shows the use of an adapter that is sometimes encountered in
old electric fixtures, the use of which requires explanation. Mention
has already been made of the various forms of lamp sockets in use
before the Edison base became a standard. In order to use an Edison
lamp in a socket intended for another form of base an adapter must be
employed to suit the new base to the old socket. In the figure the
piece _P₁_, is the adapter. This is intended to adapt the standard
lamp base to a socket that was formerly in use on the Thompson-Houston
system of electric lighting. The adapter is joined to the old socket by
the screw at _G_ and the circuit formed as already described.

=Lamp Labels.=--For many years all incandescent lamps were rated in
candlepower and were made in sizes 8, 16, 32, etc., candlepower. On
the label was printed the voltage at which the lamp was intended to
operate, and also the candlepower it was supposed to develop. Thus
110 v., 16 cp. indicated that when used on 110-volt circuit, the lamp
would give 16 candlepower of light. This label in no way indicated the
amount of energy expended. With the development of the more efficient
filaments came a tendency to label lamps in the amount of energy
consumed. This has resulted in all lamps being labeled to show the
voltage of the circuit suited to the lamp, and the watts of electricity
consumed when working at that voltage. At present a lamp label may be
marked 110 v., 40 w., which indicates that it is intended to develop
its best performance at 110 volts and will consume 40 watts at that

Commercial lamps are now manufactured in sizes of 10, 15, 25, 40, 60,
75, and 100 watts capacity for ordinary use. Of these the 40-watt
lamp probably fulfills the greatest number of conditions and is most
commonly used. Besides these there are the high-efficiency lamps of
the gas-filled variety that are made in larger sizes and the miniature
lamps in great variety. All are labeled to show the volts and the watts

=Illumination.=--The development of high-efficiency lamps has caused
a radical change in the methods of illumination. With cheaper light
came the desire to more nearly approximate the effect of daylight
in illumination. This has brought into use indirect illumination,
in which the light from the lamp is diffused by reflection from the
ceiling and walls of the room. Illuminating engineering is now a
business that has to do with placing of lamps to the greatest advantage
in lighting any desired space. In large and complicated schemes of
lighting professional services are necessary, but in household lighting
the required number of lamps for the various apartments are almost
self-evident. The lighting of large rooms, however, requires thoughtful
consideration and in many cases the only definite solution of the
problem is that of calculation.

=The Foot-candle.=--The amount of illumination produced over a given
area depends not only on the number of lamps and their candlepower, but
upon their distribution and the color of the walls and furnishings.
In the calculation of problems in illumination, units of measure are
necessary to express the amount of light that will be furnished at any
point from its source. The units adopted for such purposes are the
foot-candle and the lumen.

=The Lumen.=--A light giving 1 candlepower, placed in the center of a
sphere of 1 foot radius illuminates a sphere, the area of which is 4
× 3.1416 or 12.57 square feet. The _intensity_ of light on each square
foot is denoted as a candle-foot. The candle-foot is the standard
of illumination on any surface. The _quantity_ of light used in
illuminating each square foot of the sphere is called a lumen. A light
of 1 candlepower will therefore produce an intensity of 1 candle-foot
over 12.57 square feet and give 12.57 lumens. Therefore, if all of the
light is effective on a plane to be illuminated, a lamp rated at 400
lumens would light an area of 400 square feet to an average intensity
of 1 candle-foot.

To find the number of lamps required for lighting any space, the area
in square feet is multiplied by the required intensity in foot-candles,
to obtain the total necessary lumens, and the amount thus obtained is
divided by the effective lumens per lamp.

The bulletins of the Columbia Incandescent Lamp Works gives the
following method of calculating the number of lamps required to light a
given space:

  Number of lamps = (_S_ × _I_)/(Effective lumens per lamp)

  _S_ (square feet) × _I_ (required illumination in foot-candles)
  = total lumens.

The total lumens divided by the number of effective lumens per lamp
gives the number of lamps required. In using the formula the effective
lumens per lamp is taken from the following table:

    Watts per lamp               25   40   60  160  150  250

    Effective lumens per lamp    95  160  250  420  630  1090

    Lumens per watt             3.8  4.0  4.2  4.2  4.2   4.3

The size of the units is a matter of choice since six 400-lumen units
are equal to four 600-lumen units in illuminating power, etc. In
deciding upon the proper size of lamps to use, consideration must be
taken of the outlets if the building is already wired. In general
the fewest units consistent with good distribution will be the most
economical. The table shows the lumens effective for ordinary lighting
with Mazda lamps and clear high-efficiency reflectors with dark walls
and ceiling. Where both ceiling and walls are very light these figures
may be increased by 25 per cent.

To illustrate the use of the table, take an average room 16 by 24 to
be lighted with Mazda lamps to an intensity of 3.5 foot-candles. If
clear Holoplane reflectors are used, the values for lumens effective on
the plane may be increased 10 per cent. due to reflection from fairly
light walls. The lamps in this case are to be of the 40-watt type which
in the table are rated at 160 lumens. To this amount 10 per cent. is
added on account of the reflectors and walls. This data applied to the
formula gives:

    _s_ = 16 by 24 feet
    _I_ = 3.5
    Lumens per lamp = 160
    ((16 × 24) × 3.5)/176 = eight 40-watt lamps.

[Illustration: FIG. 219.]

=Reflectors.=--The character and form of reflectors have much to do
with the effective distribution of the light produced by the lamp.
The most efficient form of reflectors are made of glass and designed
to project the light in the desired direction. The illustration in
Fig. 219, marked open reflector, shows the characteristic features of
reflectors designed for special purposes. They are made of prismatic
glass fashioned into such form as will produce the desired effect and
at the same time transmit and diffuse a part of the light to all
parts of the space to be lighted. The greater portion of the light is
sent in the direction in which the highest illumination is desired.
The reflectors are made to concentrate the light on a small space or
to spread it over a large area as is desired. They are, therefore,
designated as intensive or extensive reflectors and made in a variety
of forms.

=Choice of Reflector.=--Where the light from a single lamp must spread
over a relatively great area, it is advisable to use an _extensive_
form of reflector. This reflector is applicable to general residence
lighting, also uniform lighting of large areas where low ceilings or
widely spaced outlets demand a wide distribution of light. Where the
area to be lighted by one lamp is smaller, the _intensive_ reflector is
used. Such cases include brilliant local illumination, as for reading
tables, single-unit lighting or rooms with high ceilings as pantries or

Where an intense light on a small area directly below the lamp is
desired, a _focusing_ reflector is used. The diameter of the circle
thus intensely lighted is about one-half the height of the lamp above
the plane considered. Focusing reflectors are used in vestibules or
rooms of unusually high ceilings.

      Type                           Height above plane to be lighted
    Extensive                                               1/2 _D_
    Intensive                                               4/5 _D_
    Focusing                                                4/3 _D_
    _D_ = distance between sides of room to be illuminated.

The various other fixtures of Fig. 219 that are designated as
reflectors are in some cases only a means of diffusion of light. In the
use of the high-efficiency gas-filled lamps the light is too bright to
be used directly for ordinary illumination. When these lamps are placed
in opal screens of the indirect or the semi-indirect form the light
produced for general illumination is very satisfactory. Considerable
light is lost in passing through the translucent glass but this is
compensated by the use of the high-efficiency lamps and the general
satisfaction of light distribution.

=Lamp Transformers.=--Lamps of the Mazda type, constructed to work at
the usual commercial voltages, are made in low-power forms to consume
as little as 10 watts; but owing to the difficulty of arranging a
suitable filament for the smaller sizes of lamps, less voltage is
required to insure successful operation. The lamps for this purpose
are of the type used in connection with batteries and require 1 or
more volts to produce the desired illumination. When these little
lamps are used on a commercial circuit, the reduction of the voltage
is accomplished by small transformers, located in the lamp socket.
The operating principle and further use of the transformers will be
explained later under doorbell transformers. The lamp transformer,
although miniature in design, is constructed as any other of its kind
but designed to reduce the usual voltage of the circuit to 6 volts
of pressure. The socket is that intended for the use of the Mazda
automobile lamp giving 2 candlepower. This lamp used with electricity
at the average rate per kilowatt can be burned for 10 hours at less
than half a cent. In bedrooms, sickrooms and other places where a
small amount of light is necessary but where a considerable quantity
is objectionable, the miniature lamp transformer serves an admirable
purpose in adapting the voltage of the commercial alternating circuit
to that required for lamps of small illuminating power. Such a
transformer is shown in Fig. 220.

[Illustration: FIG. 220.--Miniature lamp transformer complete and the
parts of which it is composed.]

The figure shows in _A_ the assembled attachment with the lamp bulb in
place. The part _B_, the transformer, changes the line voltage to that
of a battery lamp. A line voltage of 110 may be transformed to suit a
6-volt miniature lamp. The parts _C_ and _D_ compose the screw base and
the cover, in which is fitted the transformer _B_.

=Units of Electrical Measurement.=--The general application of
electricity has brought into common use the terms necessary in its
measurement and units of quantity by which it is sold. The volt, ampere
and ohm are terms that are used to express the conditions of the
electric circuit; the watt and the kilowatt are units that are employed
in measuring its quantity in commercial usage. The use of these units
in actual problems is the most satisfactory method of appreciating
their application.

As already explained the volt is the unit of electric pressure which
causes current to be sent through any circuit. The electric circuits
of houses are intended to be under constant voltage--commonly 110
or 220--but the voltage may be any amount for which the generating
system is designed. Independent lighting systems such as are used in
house-lighting plants--to be described later--commonly employ 32 volts
of electric pressure.

Opposed to the effect of the volts of electromotive force is the
resistance of the circuit, which is measured in ohms. Resistance has
been called electric friction; it expresses itself as heat and tends to
diminish the flow of current. Every circuit offers resistance depending
on the length, the kind and the size of wire used. Since the wires of
commercial lighting systems are made of copper, it can be said that the
resistance of the circuit increases as the size of the conducting wire
decreases. In large wires the resistance is small but as the size of
the wire is reduced the resistance is increased. A long attachment cord
of a flat-iron, may offer sufficient resistance to prevent the iron
from heating properly.

The ampere is the unit which measures the amount of current. The
amperes of current determine the rate at which the electricity is being
used in any circuit. The wires of a house must be of a size sufficient
to carry the necessary current without heating. Any house wire which
becomes noticeably warm is too small for the current it carries and
should be replaced by one that is larger.

The watt is the unit of electric quantity. The quantity of electricity
being used in any circuit is the product of the volts of pressure and
amperes of current flowing through the wires. The amount of current--in
amperes--sent through the circuit is the direct result of the volts of
pressure; the quantity of electricity is therefore the product of these
two factors. A 25-watt lamp on a circuit of 110 volts uses 0.227 ampere
of current.

    25 watts = 110 volts × 0.227 amperes.

Ten such lamps use

    10 × 0.227 amperes = 2.27 amperes.

The product of 110 volts and 2.27 amperes is 250 watts.

In order to express quantity of energy, it is necessary to state the
length of time the energy is to act and originally the watt represented
the energy of a volt-ampere for one second. For commercial purposes
this quantity is too small for convenient use and the hour of time was
taken instead. The watt of commercial measurement is the watt-hour and
in the purchase of electricity the watt is always understood as that

Even as a watt-hour the measure is so small as to require a large
number to express ordinary amounts and a still larger unit of 1000
watt-hours or the kilowatt-hour was adopted and has become the accepted
unit of commercial electric measurement. Just as a dollar in money
conveniently represents 1000 mills so does a kilowatt of electricity
represent a convenient quantity.

In the purchase of electricity, the consumer pays a definite amount,
say 10 cents per kilowatt. This represents an exact quantity of energy,
that may be expended in light, in heat, or in the generation of power,
all of which may be expressed as definite quantities.

As light, it indicates in the electric lamp the number of
candle-power-hours that may be obtained for 10 cents. At this rate
a single watt costs 0.01 cent an hour. A 25-watt electric lamp will
therefore cost 0.25 (1/4) cent for each hour of use; a 60-watt lamp
costs 0.6 cent per hour; the ten 25-watt lamp mentioned above using 250
watts costs 2.5 cents per hour.

As heat, it is expressed in English-speaking countries as British
thermal units, 1 kilowatt-hour representing 3412 B.t.u. per hour. One
cent’s worth of electricity at the rate given yields 341.2 B.t.u. of

As power, it represents an exact amount of work. So expressed, a watt
represents 1/746 horsepower; therefore a kilowatt is represented in
power as 1000/746 = 1.3 horsepower. Since the kilowatt purchased for
10 cents is a kilowatt-hour, the equivalent horsepower is for the same
length of time. At the assumed rate, 10 cents buys 1.3 horsepower
for one hour. When used as work it represents 2,544,000 foot-pounds
or 255,400 foot-pounds of work for 1 cent. This work when expended
in a motor, to do the family washing or perform any other household
drudgery, represents the greatest value to be derived from its use.
A 1/2-horsepower motor is amply large to operate a family washing
machine. Even though the motor is only 50 per cent. efficient its cost
of operation is less than 7 cents per hour.

=Miniature Lamps.=--Miniature electric lamps include all that are
not used for general illuminating purposes. The term applies more
particularly to the form of the base than to the voltage or candlepower
of the filament. There are three general classes of these lamps:
candelabra and decorative, that operate on lighting circuits of 100 to
130 volts and are usually intended for decorative purposes; general
battery lamps used for flash lights; and lamps for automobiles and
electric-vehicle service.


    Candelabra screw base
    Miniature screw base
    Double-contact bayonet candelabra base
    Single-contact bayonet candelabra base

FIG. 221.--Miniature lamp bases.]

The term miniature lamp applies more particularly to the base than to
the voltage or candlepower. The style of base is characteristic of the
service for which the lamp is designed rather than the size or number
of watts consumed. There are two general styles of bases: the screw
type of the Edison construction of which there are two sizes; and the
bayonet type of which there are two styles of construction.

Bases for miniature lamps are made in form to suit the conditions of
their use. The styles at present are shown in Fig. 221. Of these the
screw bases at the left are those attached to small flash-lamp bulbs
and others of the smaller sizes of lamps. The two at the right of the
figure are the bayonet style used under conditions not suited to the
screw contact. In the case of automobile lamps and in places where
vibration will cause loss of contact the bayonet base is generally in
use. The lamp is held in place by the projecting lugs that engage with
openings in the socket and kept in place by the pressure of a spring.
The contact with the lamp filament is made by two terminals that make
connection directly with the terminals of the lamp filament. The single
contact base is kept in place similarly to that of the other but makes
a single contact at the end of the socket while the other but makes a
single contact at the end of the socket while the circuit is completed
through the pressure exerted between the projecting lugs and the socket.

=Effect of Voltage Variations.=--Voltage variation may be temporary,
due to changing load in the circuit, or in constantly overloaded
circuits the voltage may be constantly below normal. The change in
electric pressure affects in a considerable degree the amount of light
given by the lamp. As an example, a 5 per cent. drop from the normal
voltage will cause a decrease of 31 per cent. in the amount of light
given. This means that if a lamp is working on a circuit of 110 volts
and the voltage from any cause were to drop to 104-1/2 volts, the light
would decrease 6.8, almost 7 candlepower. Drop in voltage may also be
due to the resistance of wires that are too small for the service.
Lamps attached to such a circuit will constantly burn dim.

=Turn-down Electric Lamps.=--The ordinary incandescent lamp lacks the
flexibility of gas and oil lamp, in that the amount of light cannot be
varied at will. This feature is attained in the electric turn-down lamp
either by resistance added to the lamp circuit or by the use of two
separate filaments in a single globe; one of ordinary lamp size and the
other of such size that it consumes only a fraction as much energy as
the normal lamp.

[Illustration: FIG. 222.--Sectional view of a “turn-down” lamp socket.]

Turn-down lamps of the latter form are made in several styles, the
chief points of difference being in the method of changing the contact
from the high-to the low-power filament. In Fig. 222 a sectional view
shows the “pull-string” form of lamp in which the parts are exposed.
The long filament _H_ and the smaller one _L_ represent two individual
lamps of different lighting power. The change in light is made from one
to the other by pulling the string which is attached to a switch in
the socket and which changes the contact to send the current through
the filament giving the desired amount of light. The figure shows a
carbon-filament lamp, but tungsten lamps are made to accomplish the
same purpose. The difficulty of manufacturing a 1-candlepower tungsten
lamp for direct operation on a 110-volt circuit requires the filaments
to work in series. The figure is arranged on the same plan as for a
tungsten lamp.

The lamp base when screwed into the socket makes contact with the two
service wires of the circuit at _A_ and at _E_, which are part of the
screw base. To light the lamp the current is switched on as in any
lamp. The current enters at _A_ and passes down the connecting piece to
the contact _B_. The piece _B_ is moved by the cord to light either the
large or the small filament. In the position shown the current enters
the small filament at _C_ and in order to complete the circuit to _E_
must traverse both the large and the small filament. The resistance
of the small filament is such that the passing current raises it to
a temperature of incandescence but the large filament does not heat
sufficiently to give an appreciable amount of light. When the cord is
pulled to light the large filament, the contact is made at _D_ and the
current passes directly through the large filament to complete the
circuit at _E_.

Turn-down lamps are especially adapted to the home. Their use in a
child’s bedroom or sick chamber is a great convenience. The lamps are
often constructed with a long-distance cord extending from a fixture to
the bedside. By this means a dim or bright light is given as desired,
with the least inconvenience. Turn-down lamps are made in a variety
of sizes. The large filaments are arranged to give 8, 16, and 32
candlepower. With the 8-candlepower lamp the small filament gives 1/2
candlepower and with the 16-and 32-candlepower the small filament gives
1 candlepower.

With the lamps described, the variation in amount of light is attained
by changing the contacts, to bring into action filaments of different
resistances. They admit of only two changes, either the lamp burns
at full capacity or at the least light the lamp will give. The heat
liberated by the large filament, when the small light is in use, takes
place inside the lamp globe.

=The Dim-a-lite.=--In another form of turn-down lamp the change in
amount of light is produced by external resistance in the circuit.
The resistance is furnished by a coil of wire which is enclosed in a
special lamp socket. It possesses the advantage as a turn-down lamp
in a number of changes of light. The added resistance in a socket
decreases the flow of current and, therefore, the filament gives less
light. The resistance wire is divided into a number of sections and
contact with the terminals of these sections decreases the light with
each addition of resistance. The heat generated in the resistance coils
is dissipated by the brass covering of the socket.

[Illustration: FIG. 223.--The resistance type of “turn-down” lamp.]

An illustration of a turn-down lamp using a separate resistance is
that of Fig. 223, known commercially as the Dim-a-lite, which is an
excellent example. The Dim-a-lite attachment is a lamp socket in which
is enclosed a miniature rheostat or resistance unit. The lamp, when
placed on the Dim-a-lite, makes electrical contact as in an ordinary
socket but with the difference that in series with the lamp filament
is the rheostat, by means of which additional resistance may be added
to change the current flowing in the lamp. The rheostat is so arranged
that contact may be made at four different points in the resistance
coil, through which the electricity may be varied from 100 to 20 per
cent. of the normal quantity. The resistance in any case permits
current to pass through the filament in amounts of 70, 30 and 20 per
cent. of the normal amount. In use, the variation is made by pulling
one string to add resistance and thus dim the light; or by pulling the
other string, the resistance is decreased and more electricity passes
through the filament to produce a brighter light. The quantity of light
given out by the filament does not vary in the ratio of the added
resistance but a variable light is obtained at the expense of a small
amount of electricity which is changed into heat. When the light is
burning at its dimmest only 20 per cent. of the normal current is used.
Under this condition the light given out by filament does not express
the high efficiency attained when the lamp is burning at its full power
but it does give a convenient form of light regulation with the minimum
waste of energy.

=Gas-filled Lamps.=--Until 1913 the filaments of all Mazda lamps
operated in a vacuum. The vacuum serving the purpose of preventing
oxidation and at the same time it reduced the energy loss to the least
amount. It was found, however, under some conditions of construction
that lamps filled with inert gas gave a higher efficiency and
more satisfactory service than those of the vacuum type. In this
construction, the filament is operated at a temperature much higher
than that of the vacuum lamp and as a consequence gives light at a
less cost per candlepower. Mazda vacuum lamps are now designated by
the General Electric Co. as Mazda B lamps, Fig. 224, and those of the
gas-filled variety, Fig. 225, are designated as Mazda C lamps.

[Illustration: FIG. 224.--40-watt Mazda B lamp (1/2 scale).]

[Illustration: FIG. 225.--750-watt Mazda C lamp (1/4 scale).]

The filaments of the gas-filled lamps are intensely brilliant and
where they come within the line of vision should be screened from the
eyes. The high efficiency of these lamps permit the use of opal shades
to produce a desired illumination at a rate of cost that compares
favorably with the unscreened light of the vacuum lamps.

=Daylight Lamps.=--The color of the light from an incandescent electric
lamp depends on the temperature of the filament. In the case of the
gas-filled Mazda lamp the high filament temperature produces a light
that differs markedly from the vacuum lamps in that it contains a
greater amount of blue and green rays. It is therefore possible to
produce light that is the same as average daylight. Gas-filled lamps
with globes colored to produce light of noonday quality are produced at
an expenditure of 1.2 watts per candlepower.

In the matching of colors, it should be kept in mind that the tint of
any color is influenced by the kind of light by which it is viewed.
Colors matched by ordinary incandescent light containing a large
percentage of red rays cannot produce the same effect when the same
articles are seen in light of different quality. The daylight lamps are
therefore intended to be used under conditions that require daylight

=Miniature Tungsten Lamps.=--The wonderful light-giving properties of
tungsten has made possible the use of miniature incandescent lamps for
an almost infinite variety of usages. The miniature lamps are similar
in action to other incandescent electric lamps except that they are
operated on voltages lower than is used on commercial circuits. When
used on commercial circuits, incandescent tungsten lamps of less than
10 watts capacity require filaments that are too delicate to withstand
the conditions of ordinary use. The properties of tungsten are such
that the passage of only a small amount of current is required to
render the filament incandescent. In the case of a 110-volt circuit,
a 10-watt lamp requires only 0.09+ ampere to produce the desired
incandescence. It will be remembered that the watt is a volt-ampere and
the 10-watt lamp will then require

    110 volts × 0.09 + ampere = 10 watts.

Since 10-watt lamps are the smallest units that may be used on 110-volt
circuits, their employment in smaller sizes must be such as will give
more stable filaments. This is possible when the lamps are used at
lower voltage. A 10-watt lamp on a 10-volt circuit will require an
ampere of current.

    10 volts × 1 ampere = 10 watts.

A filament suitable for an ampere of current is shorter and heavier
than that of the 110-volt lamp and therefore furnishes a good form of
construction. Still lower voltages may be used with filaments suited to
the quantity of light desired.

In the case of battery lamps that are intended to operate on 1 or more
volts, the filaments are made in size and length to suit the condition
of action. In all cases the product of the volts and amperes give the
capacity of the lamp in watts.

Miniature lamps are ordinarily marked to show the voltage on which they
are intended to operate. A 6-volt battery lamp is intended to be used
with a primary battery of four to six cells depending on the condition
of usage, or three cells of storage battery, each cell of which gives 2
volts of pressure.

=Flash Lights.=--These are portable electric lamps composed of a
miniature incandescent bulb, which with one or more dry cells are
enclosed in a frame to suit the purpose of their use. They are made
in pocket sizes or in form to be conveniently carried in the hand and
are convenient and efficient lamps wherever a small amount of light is
required for a short time. The electricity for operating the lamp is
supplied by a battery of dry cells (to be described later), or by a
single dry cell. In each case the incandescent bulb is suited to the
voltage of the battery.

In replacing the bulbs care must be taken to see that the voltage is
that suited to the battery. The voltage is usually stamped on the lamp
base or marked on the bulb. In case a lamp intended for a single cell
is used with a battery of three or four cells, the lamp filament will
soon be destroyed. The reverse will be true should a lamp intended
for a battery be used with a single cell. The single cell giving not
much more than a volt of electromotive force will not send sufficient
current through the lamp filament to render it incandescent.

=The Electric Flat-iron.=--The changes that have been made in domestic
appliances by the extended use of electricity have brought many
innovations but none are more pronounced than the improvements made
in the domestic flat-iron. It was the first of the household heating
devices to receive universal recognition and its place as a domestic
utility is firmly established.

The relatively high cost of heat as generated through electric energy
is in a great measure counterbalanced in the flat-iron by high
efficiency in its use. In the electric iron, the heat is developed
in the place where it can be used to the greatest advantage, and
transmitted to the face of the iron with but very little loss. Because
of this direct application the cost of operation is but slightly in
excess of the other methods of heating.

The electric flat-iron has now become a part of the equipment of every
commercial laundry, where electricity can be obtained at a reasonable
rate. The popularity of the electric iron is due to its cleanliness
and to the increased amount of work that may be accomplished through
its use. Because of the time saved in changing irons and the comfort
of the room by reason of its lower temperature, a sufficiently greater
amount of work is accomplished to more than compensate for the greater
cost of heat.

The electric current is conducted to the flat-iron from the house
circuit by wires made into the form of a flexible cord. The cord
attaches to the electric-lamp fixture by a screw-plug and connects with
the iron by a special attachment piece as indicated at _P_ and _R_ in
Fig. 226. Connection is made to an incandescent lamp socket at any
convenient place. The only precaution necessary in attaching the iron
is to see that the fuse and the wires, which form the circuit, are of
size sufficient to transmit the amount of current the iron is rated to
use. As explained later, the fuse which is a part of every electric
house circuit, and the conducting wires which form the heater circuit,
must be sufficient in size to transmit the necessary current without
material heating.

[Illustration: FIG. 226.--Electric flat-iron and its attachments.]

The cord connects with the socket at _P_, and the current turned on. It
is attached with the iron by a piece _R_, made of non-conducting and
heat-resisting material and arranged to make contact with the heater
terminals by two brass plugs that are insulated from the body of the
iron and afford easy means of making electric contact. The contact
plugs are shown in Fig. 227. To make electric connection, the contact
piece is simply pushed over the plugs, where it is held in place by
friction. Instructions which accompany a flat-iron when purchased
advise that the attachment piece be used in turning off the current.
The reason for this is because of the flash that accompanies the break
in the circuit when disconnection is made in the socket. This flash
is really a small electric arc, that forms as the circuit is broken
and which burns away the switch at the point of disconnection. The arc
so formed burns away the contact pieces in the switch and it is soon
destroyed. The attachment piece will stand this wear more readily than
the socket switch and hence is preferable for disconnecting. The irons
are frequently provided with a special switch for the service required
in the flat-iron.

[Illustration: FIG. 227.--Electric flat-iron showing position of the
heating element and contact plugs.]

A spiral spring connected to the attachment cord prevents it from
kinking when in use and thus breaking the conducting wires. The
attachment cord is made of stranded wires to make it flexible. The
strands of fine copper wire are made to correspond to the gage numbers
by which the various sizes of wire are designated. In use the constant
movement of the iron tends to kink the cord and thus breaks the
strands. This action is most pronounced at the point where the cord
attaches to the iron. For this reason a spiral spring wire encloses the
cord for a short distance above the attachment piece. After long usage
the cord is apt to break in this vicinity. It may usually be repaired
by cutting off the ends of the cords and new connections made in the
attachment piece. When the iron is in use the slack portion of the cord
is kept from interfering with the work by the coiled wire _S_, which
connects with the cord at any convenient place.

Electric flat-irons are made in a variety of styles and forms, the
mechanism of each possessing some particular advantage, but all are
provided with the same essential parts, chief of which is the heater
with its electric attachment piece. In Fig. 228 is shown very clearly
the construction of an example in which attention is called to the
points of excellence that are required in a particularly serviceable
iron. The form of the heating element which is recognized in the iron
is also shown in Fig. 228.

[Illustration: FIG. 228.--Electric flat-iron heating element.]

In the figure the heater is made of coils of resistance wire, wound
on a suitable frame of mica. The heating element is insulated from
the body of the iron with sheets of mica, this being a material
that makes an excellent insulator and is not materially affected by
the heat to which it is subjected. The resistance wire of which the
element is composed is especially prepared to resist the corroding
action common to metal when heated in air. The form of the element is
such as to permit the least movement of the turns of wire--in their
constant heating and cooling--that will allow the different spires to
make contact and thus change the resistance. Should the spires of wire
come together, the current would be shunted across the contact and the
resistance of the element decreased. The effect of such a reduction of
resistance would be an increased flow of current and a corresponding
increase of heat. In this, as in the electric lamp and all other
electric circuits, the current, voltage and resistance follow the
conditions of Ohm’s law.

Different sizes of irons will, of course, require different amounts of
current. A 6-pound iron, such as is commonly used for household work,
will take about 5 amperes of current at 110 volts pressure. The amount
of electricity the iron is intended to consume is generally stamped on
the nameplate of the manufacturer. This is specified by the number of
volts and amperes of current the iron is rated to use. As an example,
the iron may be marked, Volts 105-115, Amperes 2-3. This indicates
that the iron is intended to be used on circuits that carry electric
pressure varying from 105 to 115 volts and that the heater will use
from 2 to 3 amperes of current, depending on the voltage.

To estimate the cost of operating such an iron, it is necessary to
determine the number of watts of electric energy consumed. The number
of watts of energy developed under any condition will be the product of
the volts times the amperes. Suppose that in the above example the iron
was used on a circuit of 110 volts. Under this condition the current
required to keep the iron hot would be 2.5 amperes. The product of
these two qualities, 110 × 2.5 is 275 watts. If the cost of electricity
is 10 cents per kilowatt-hour (1000 watts) the cost of operating the
iron would be

    275/1000 × 10 cents = 2-3/4 cents an hour.

Since the electric iron requires a much larger amount of current than
is usually required for ordinary lighting, the circuit on which it is
used should receive more than passing attention. The wires should be
of size amply large to carry without heating the current necessary for
its operation. This topic will be discussed later but it is well here
to call attention to the necessity for a circuit suited to the required
current. If an iron requiring 5 amperes of current is attached to a
circuit that is intended to carry only 3 amperes the conducting wires
will be overheated and may be the cause of serious results.

=The Electric Toaster.=--As shown in Fig. 229 the toaster is made of
a series of heating elements mounted on mica frames and supported on
a porcelain base. It is an example of heating by exposed wires and
direct radiation. The heaters _H_ are coils of flat resistance wire
that are wound on wedge-shaped pieces of mica. They are supported on a
wire frame that is formed to receive slices of bread on each side of
the heaters. The attachment piece _A_ and the material of the heater is
similar in construction to that of the flat-iron. The electric circuit
may be traced from the contacts at _A_ and _B_ in the attachment plug
by the dotted lines which indicate the wires in the porcelain base.
The current traverses each coil in turn and connects with the next,
alternately at the top and bottom. The resistance is such as will
permit the voltage of the circuit to send through the coils current
sufficient to raise the heaters to a red heat. The added resistance of
the hot wires decreases the flow of current to keep the temperature at
the desired degree.

[Illustration: FIG. 229.--The electric toaster.]

In a heater of this kind the resistance of the wire may increase with
age and the coils fail to glow with a sufficient brightness. The
reason for the lack of heat is that of decrease in current, due to the
increased resistance of the wires. This condition may be corrected by
the removal of a little of the heater coils. If a turn or two of the
heater wire is removed, the resistance of the circuit is reduced and
the effect of the increased current will produce a higher temperature
in the heater.

=Motors.=--As a means of developing mechanical power in small units,
the electric motor has made possible its application in many household
uses that were formerly performed entirely by manual labor. As a
domestic utility electrical power is generated at a cost that is the
least expensive of all its applications. As a means of lighting and
heating electricity has had to compete with established methods and has
won place because of the advantages it possesses over that of cost.
In the development of domestic power it has practically no opponent.
There is no other form of power that can be so successfully utilized
in delivering mechanical work for the purposes required. A kilowatt of
electric energy, for which 10 cents is a common price, will furnish a
surprising amount of manual labor. Theoretically, 746 watts is equal to
1 horsepower. The commercial kilowatt is rated at an hour of time, and
is, therefore, equal theoretically to 1-1/3 horsepower for one hour.
While motors cannot be expected to transform all of this energy into
actual work without loss, even at the low rate of efficiency attained
by the small electric motor, they furnish power at a relatively small

The first applications of electric power were those for sewing
machines, fans, washing machines, etc. Its use has made possible the
vacuum cleaner, automatic pumping, refrigeration, ventilation, and many
other minor uses as the turning of ice-cream freezers, churning and
rocking the cradle.

Electric motors are made in many sizes for power generation and in
forms to suit any application. They are made to develop 1/30 horsepower
and in other fractional sizes for both direct and alternating current.

In applying mechanical power to any particular purpose special
appliances must be made to adopt electric motors to the required work.
This is accomplished in all household requirements. The motors are made
to run at a high rate of speed and must be reduced in motion by pulleys
or gears to suit their condition of operation. As in the case of
electric lamps they must be suited to the voltage and type of current
of the circuit on which they are to be used.

Commercial electric circuits furnish electricity in two types, direct
current, ordinarily termed D.C., and A.C. or alternating current. The
terms direct and alternating current apply to the direction of the
electric impulses which constitute the transmitted energy. In the
electric dynamo, the generation of the current is due to impulses that
are induced in the wires of the dynamo armature as they pass through a
magnetic field of great intensity. These electric impulses are directed
by the manner in which the wires cut across the lines of force which
make up the magnetic field. In the case of the direct current the
impulses are always in the same direction through the circuit, while
in the other they are induced alternately to and fro and so produce
alternating current.

The term electric current is used only for convenience of expressing
a directed form of energy. Since nothing really passes through the
wires but a wave of energy, the effect is the same whether the electric
impulses are in the same or in opposite directions. An incandescent
lamp will work equally well on an A.C. or a D.C. circuit of the proper
voltage; but in the case of motors the form of construction must be
suited to the kind of current. Both A.C. and D.C. commercial circuits
are in common use, the units of measurement are the same for each but
in ordering a motor it is necessary to state the type of current and
the voltage, in order that the dealer may supply the required machine.
In the case of an alternating motor it is further necessary to state
the number of cycles of changes of direction made per second in the
A.C. circuit. All of this information may be obtained by inquiring of
a local electrician or of the power station from which the current is

There is still another item of information necessary to be supplied
with an order for a motor, other than those of fractional horsepower.
With motors of a horsepower or more it is necessary to state the number
of phases included in the circuit. This information to be complete must
state whether the motor is to operate on a single-phase, two-phase, or
three-phase circuit. These terms apply to a condition made possible in
A.C. generation that permits one, two, or three complete impulses to be
developed in a circuit at the same time. These phases are transmitted
by three wires, any two of which will form a circuit and give a supply
of energy at the same voltage. Either one phase or all may be used at
the same time and for this reason the phase of an A.C. motor should be
given in an order. To make the information complete there should be
included the number of cycles or complete electric impulses per second
produced in the circuit. Suppose that a 1-horsepower motor is required
to work on an A.C. circuit of 110 volts. Inquiry of the electric
company reveals that the circuit is three-phase at 60 cycles per
second. The dealer on receiving this information will be able to send
a motor to suit your conditions. Most A.C. motors of 1 horsepower or
less are of the single-phase variety. In the case of D.C. motors it is
necessary only to state the voltage of the circuit to make the required
information complete.

=Fuse Plugs.=--Every electric circuit is liable to occurrences known as
short-circuiting or “shorting.” This is a technical term describing a
condition where, by accident or design, the wires of a circuit are in
any way connected by a low-resistance conductor or by coming directly
into contact with each other. In case of shorting, the resistance is
practically all removed and the amount of current which flows through
the circuit is so great as to produce a dangerous amount of heat in the
wires. If the covering of a lamp cord becomes worn so as to permit the
bare wire of the two strands to come together, a “short” is produced.
Immediately, the reduced resistance permits the electric pressure to
send an amount of current through the wires, greater than they are
intended to carry. When this occurs an electric arc will form at the
point of contact with the accompanying flash of vaporizing metal and
the wire will finally burn off. Fires started from this cause are not

To guard against accidents from short-circuiting, every electric
circuit should be provided with fuses which, in cases of emergency,
are intended to melt and thus break the circuit. Fuses are made of
lead-composition or aluminum and are used in the form of wire or
ribbon-like strips, of sizes that will carry a definite amount of
current. They are designated by their carrying capacity in amperes. As
an example: a 2-ampere fuse will carry 2 amperes of current without
noticeable heating, but at a dangerous overload the fuse will melt and
the circuit be broken. Should a short-circuit be formed at any time,
the rush of current through the fuse will cause it almost immediately
to melt, and stop the flow of current. They are, therefore, the
safeguard of the circuit against undue heating of the conducting wires.

When an open fuse blows (melts), the heat generated by the arc,
formed at the breaking circuit, is so sudden that there is frequently
an explosive effect that throws the melted metal in all directions,
and in case it comes into contact with combustible material a fire
may result. To do away with this danger, fire insurance companies in
their specifications of electric fixtures state what forms of fuses
will be acceptable in the buildings to be insured. These specifications
are known as the Underwriters Rules and may be obtained from any fire
insurance company. The fuses, or fuse plug, as they are commonly
called, generally occupy a place in a cabinet or distributing panel,
near the point where the lead wires enter the building. The cabinet
contains the porcelain cutouts for sending the current through the
different circuits; the fuse plugs form a part of the cutouts, one fuse
to each wire. The cabinet contains besides the cutouts a double-poled
switch to be used for shutting off the current from the building when

[Illustration: FIG. 230.--Electric cabinets.]

Cabinets for this purpose are made in standard form of wood or steel
to suit the condition of service. These cabinets may be obtained from
any dealers in electrical supplies or the cabinet may be made a part
of the house since they are only small shallow closets. Fig. 230
represents such a cabinet as is used in the average dwelling. It is
made of a light wooden frame set between the studding of a partition
at any convenient place. The bottom of the cabinet is made sloping to
prevent its being used as a place of storage for articles that might
lead to trouble. The cabinet is sometimes lined with asbestos paper as
a prevention from fire but this is not necessary as the fuse plugs and
their receptacles, when of approved design, are sufficient to prevent

The main wires which supply the house with electricity--marked lead
wires--are brought into the cabinet as shown in Fig. 231 and attached
to the poles of the switch _S_. In passing through the switch the lead
wires each contain a mica-covered fuse plug _F_, that will be described
later. The current at any time may be entirely cut off from the house
by pulling the handle _H_, which is connected by an insulating bar
and the contacts _N_ of the switch. When the handle _H_ is pulled to
separate the contact pieces, all electric connection is severed at that

[Illustration: FIG. 231.--Electric panel containing cutout blocks,
fuses and switch.]

The wattmeter for measuring the current is placed at the points
marked _meter_, as a part of the main circuit. The main wires in the
cabinet terminate in the porcelain cutouts, from which are taken off
the various circuits of the house. In the figure, three such cutouts
are shown making three circuits marked 1, 2, and 3. In circuit No. 1,
the fuses are marked _F_. These wires are joined to the main wires at
the points marked _C_ and _C´_. The number of circuits the house will
contain depends on the number of lights and the manner in which they
are placed. The circuits are intended to be arranged so that in case of
a short, no part of the house will be left entirely in darkness.

Fuses for general use are made in two different types--the plug type
and the cartridge type--each of which conforms to the rules of the
Underwriters Association. Those most commonly used for house wiring
are the plug type shown in Fig. 232 and indicated in the figure just
described. These plugs are made of porcelain and provided with a screw
base which permits their being screwed into place like an incandescent
lamp. The front of the plug is arranged with a mica window which allows
inspection to be made in case of a short, the blown fuse indicating
the circuit in which the trouble is located. Another style of the same
type of plug, known as the re-fusable fuse plug, permits the fuse to be
replaced after the wire has been destroyed by a short.

[Illustration: FIG. 232.--Mica covered fuse plug.]

[Illustration: FIG. 233.--Cartridge fuse.]

[Illustration: FIG. 234.--Plug receptacle for cartridge fuse.]

The second type is commonly known as the cartridge fuse plug from its
general appearance. This fuse is shown in Fig. 233. The fusable wire
is enclosed in a composition fiber tube, the ends of which are covered
by brass caps which afford contact pieces in the fuse receptacle and
to which are fastened the ends of the fuse wire. These fuses are very
generally employed in power circuits and others of large current
capacity. The small circle in the center of the label is the indicator.
When the fuse burns out, a black spot will appear in the circle. It
is sometimes desirable to use the cartridge fuse plug in receptacles
intended for the mica-covered type. The use of the cartridge fuses
under this condition is effected by use of a porcelain receptacle such
as is shown in Fig. 234; the cartridge fuse is simply inserted into the
receptacle which is then screwed into the socket in place of the mica

In order to avoid any possible chance of overloading the wires of
a circuit, fuses are installed which are suited to the work to be
performed. Suppose that there are ten 40-watt lamps that may be used
on a circuit, each lamp of which requires 4/11 ampere of current.

    110 × C = 40 watts

    C = 40/110 = 4/11 ampere per lamp.

Ten such lamps require ten times 4/11 ampere or 40/11 = 3.7 amperes to
supply the lamps.

A fuse that will carry 3.7 amperes of current will supply the circuit
but a 5-ampere fuse will permit an increase in the size of the lamp and
will fulfill all the necessary conditions. If, however, an electric
heater requiring 7 amperes were attached to the circuit, the fuse being
intended for only 5 amperes would soon burn out. When a fuse burns out
it must be replaced either with an entirely new receptacle or the fuse
wire must be replaced.

It sometimes happens that in case of a blown fuse there is no extra
part at hand and a wire of much greater carrying capacity is used in
its place. It should be remembered that in this practice of “coppering”
a blown fuse, has taken away the protection against short-circuiting
with its possibility of mischief.

When a short occurs, the cause should be sought for. It cannot be
located and on being replaced a second fuse blows, the services of an
electrician should be secured.

=Electric Heaters.=--All electric heating devices--whether in
the form of hot plates, ovens, stoves or other domestic heating
apparatus-possess heating elements somewhat similar to the flat-iron
or the toaster. The construction of the heating element will depend
on the use for which the heater is intended and the temperature to be
maintained. Hot plates similar to that of Fig. 235 are made singly or
two or more in combination. When the heat is to be transmitted directly
by radiation the heating coils are open, as with the toaster. Under
other conditions the coils are embedded in enamel that is fused to a
metal plate. In elements of this kind the heat is transmitted to the
plate entirely by conduction from which it is utilized in any manner
requiring a heated surface. The form of the heating element will,
therefore, depend on the application of the heat, whether it is by
direct radiation or by a combination of radiation and conduction.

Electric ovens are constructed to utilize electric heat in an insulated
enclosure. Heat derived from electricity is more expensive than from
other sources but when used in insulated ovens it may be made to
conveniently perform the service of that derived from other fuels.
In electric ovens the heaters are attached to inside walls. As in
other heating elements they are arranged to suit the conditions for
which the oven is to be used. The heaters are usually so divided as
to permit either all of the heaters to be used at the same time to
quickly produce a high temperature, or only a portion of the heat to
be used in keeping up the temperature lost by radiation. Ovens of this
kind may be provided with regulators by means of which the heat may
be automatically kept at any desired temperature. Such heating and
temperature regulation may be used to produce any desired condition,
but in practice the cost of the heat is the factor which determines its
use. Unless electric heat is conserved by insulation it cannot become a
competitor with other forms of heating.

[Illustration: FIG. 235.--Electric three-burner hot plate. Electric hot

Electric cooking stoves and ranges are made for every form of domestic
and culinary service. They fulfill many purposes that may be obtained
in no other way. As conveniences, the cost of heat becomes of secondary
consideration and their use is constantly increasing. In Fig. 236 is
an example of a time-controlled and automatically regulated electric
range. In the picture is shown separately all of the heaters for the
ovens and stove top. The part _S_ shows the switches attached to the
heaters of the stove top, which is raised to show the connecting wires.
In the larger oven there are two heaters of 1000 watts each, and in the
smaller oven one heater of 850 watts. Each heater may be controlled
separately with a switch giving three regulations of heat--high, medium
and low. The advantage of this arrangement lies in the fact that one
can set the two heaters in the oven at different temperatures which
will permit either a slow or quick heat, but when the predetermined
temperature is reached the current will be automatically cut off by the
circuit-breakers. Such flexibility of heat control in the ovens permits
the operator to apply heat at both top and bottom for baking and
roasting at just the desired temperature. This arrangement also avoids
the danger of scorching food from concentration of heat, and warping
utensils or the linings of the oven. All oven heaters on the automatic
ranges are further controlled and mastered by the circuit-breakers.

[Illustration: =Fig. 236.=--Electric range. Showing how all parts can
be removed for cleaning and replacement.]

=Intercommunicating Telephones.=--This form of telephone is used
over short distances such as from room to room in buildings or for
connecting the house with the stable, garage, etc. It is complete, in
that it possesses the same features as any other telephone but the
signal is an electric call-bell instead of the polarized electric bell
used in commercial telephone service.

Any telephone is made to perform two functions: (1) that of a
signal with which to call attention; and (2) the apparatus required
to transmit spoken words. In the intercommunicating telephone or
interphone, the signal is made like any call-bell and parts are similar
to those described under _electric signals_. The bell-ringing mechanism
is included in the box with the transmitting apparatus and the signal
is made by pressing a push button. It is not suitable for connecting
with public telephones. Telephone companies, as a rule, do not permit
connection with their lines any apparatus which they do not control.

The interphone of Fig. 237 shows the instrument complete except the
battery. This form of instrument is inexpensive, easy to put in, simple
to operate and supplies a most excellent means of intercommunication.
Complete directions for installation are supplied with the phones by
the manufacturers.

[Illustration: FIG. 237.--The intercommunicating telephone.]

=Electric Signals.=--Electrical signaling devices for household use, in
the form of bells and buzzers, are made in a great variety of forms and
sizes to suit every condition of requirement. The vibrating mechanism
of the doorbell is used in all other household signals except that of
the magneto telephone. It is an application of the electromagnet, in
which the magnetism is applied to vibrate a tapper against the rim of a

A bell system consists of the gong with its mechanism for vibrating
the armature, an electric battery or A.C. transformer connected to
the magnet coils to form an electric circuit and a push button which
serves to close the circuit whenever the bell is to be sounded. The
bell system is an open-circuit form of apparatus; that is, the circuit
is not complete except during the time the bell is ringing. By pressing
the push button the circuit is closed and the electric current from
the battery flows through the magnet and causes the tapper to vibrate.
When the push button is released the circuit is broken and the circuit
stands open until the bell is to be again used. The parts of the bell
mechanism are shown in Fig. 238 where with the battery, the push
button and the connecting wires is shown a complete doorbell outfit.
These parts may be placed in different parts of the building and
connected by wires as shown in the Fig. 239. The bell is located at
_R_, in the kitchen. The battery is placed in the closet at _B_, the
connecting wires are indicated by the heavy lines; they are secured
to any convenient part of the wall and extend into the basement and
are fastened to the joists. The wires terminate in the push button
_P_, where they pass through the frame of the front door. The wires
are secured by staples to keep them in place. Each wire is fastened
separately to avoid the danger of short-circuiting. If both wires are
secured with a single staple there is a possibility of the insulation
being cut and a short produced across the staple.

[Illustration: FIG. 238.--Diagram showing the parts of an electric

The battery _B_, in Fig. 238, is a single dry cell but more commonly
it is composed of two dry cells joined in series. It is connected,
as shown in the figure, to the binding posts _P₁_ and _P₂_ of the
vibrating mechanism, the push button _PB_ serving to make contact when
the circuit is to be closed. When the button is pressed the circuit
is complete from the + pole of the battery cell through the binding
post _P₁_, across the contact _F_, through the spring _A_, through
the magnet coils _M_, across the binding post _P₂_ and push button to
the-pole of the cell. The vibration of the tapper is caused by the
magnetized cores of the coils _M_. When the electric current flows
through the coils of wire, the iron cores become temporary magnets.
This magnetism attracts the iron armature attached to the spring _A_,
and it is suddenly pulled forward with energy sufficient to cause the
tapper to strike the gong. As the armature moves forward, the spring
contact at _F_ is broken and the current stops flowing through the
magnet coils. When the current ceases to flow in the magnet coils, the
cores are demagnetized and the armature is drawn back by the spring _A_
to the original position. As soon as the contact is restored at _F_ a
new impulse is received only to be broken as before. In this manner the
bell continues ringing so long as the push button makes contact. The
screw at _F_ is adjusted to suit the contact with the spring attached
to the armature. The motion of the armature may be regulated to a
considerable degree by this adjustment. When properly set the screw is
locked in place by a nut and should require no further attention.

[Illustration: FIG. 239.--Example of an electric doorbell installation.]

Electric bells vary in price according to design and workmanship. A
bell outfit may be purchased complete for $1 but it is advisable to
install a bell of better construction, as few pieces of household
mechanism repay their cost in service so often as a well-made bell.
The bell should be rigid, well-constructed, and the contact piece _F_
should be adjustable. This part _F_, being the most important of the
moving parts of the bell, is shown separately in Fig. 240. Only the
ends of the magnet coils with their cores are shown in the figure. The
contact is made at _A_, by the pressure of the spring against the end
of the adjustable screw _D_. When the screw is properly adjusted it is
locked securely in place by the nut _G_. The screw _D_ is held with
a screw-driver and the nut _G_ forced into position to prevent any
movement. If the screw is moved, so that contact is lost at _A_, the
bell will not ring. In the better class of bells the point of the screw
and its contact at _A_ are made of platinum to insure long life. With
each movement of the armature a spark forms at the contact which wears
away the point, so that to insure good service these points must be
made of refractory material.

[Illustration: FIG. 240.--Diagram of the vibrating mechanism used in
buzzers and doorbells.]

=Buzzers.=--Electric bells are often objectionable as signal calls
because of their clamor, but with the removal of the bell the vibrating
armature serves equally well as a signal but without the undesirable
noise. With the bell and tapper removed the operating mechanism of such
a device works with a sound that has given to them the name of buzzers.
Fig. 241 illustrates the form of an iron-cased buzzer for ordinary
duty. The working parts are enclosed by a stamped steel cover that
may be easily removed. The mechanism is quite similar to that already
described in the doorbell and Fig. 240 shows in detail the working
parts. The noise, from which the device takes its name, is produced by
the armature and spring in making and breaking contact.

=Burglar Alarms.=--A burglar alarm is any device that will give notice
of the attempted entrance of an intruder. It is usually in the form
of a bell or buzzer placed in circuit with a battery, as a doorbell
system, in which the contact piece is placed to detect the opening of
a door or window. The contact is arranged to start the alarm whenever
the window or door is opened beyond a certain point. The attachment
shown in Fig. 242 is intended to form the contact for a window. It
is set in the window frame so that the lug _C_ will be depressed and
close the alarm circuit in case the sash is raised sufficiently to
admit a man. Each window may be furnished with a similar device and the
doors provided with suitable contacts which together form a system to
operate in a single alarm. During the time when the alarm is not needed
it is disconnected by a switch. The windows and doors are sometimes
connected with an annunciator which will indicate the place from which
an alarm is given. An annunciator used for this purpose designates the
exact point at which the contact is made and removes the necessity of
searching for the place of attempted entrance.

[Illustration: FIG. 241.--The electric buzzer.

FIG. 242.--Contact for a window burglar alarm.

FIG. 243.--Trip contact which announces the opening of a door.

FIG. 244.--Contact for a door alarm.

FIG. 245.--Doorway or hall matting with contacts for electric alarm.]

In Fig. 243 is illustrated one form of door trip which may be used on
a door to announce its opening. This trip makes electric connection in
the alarm circuit when the opening door comes into contact with the
swinging piece _T_, but no contact is made as the door closes. The
trip is fastened with screws at _D_ to the frame above the door. The
opening door comes into contact with _T_ and moves it forward until the
electric circuit is formed at _C_; after the door has passed, a spring
returns it to place. As the door is closed, the part _T_ is moved
aside without making electric contact.

Fig. 244 is another form of door alarm that makes contact when the
door is opened and remains in contact until the door is closed. The
part _P_ is set into the door frame of the door in such position that
the contact at _C_ is held open when the door is closed. When the door
is opened a spring in _C_ closes the contact and causes the alarm to
sound. It continues to sound until the door is closed and the contact
is broken. When the use of the alarm is not required, the contact-maker
is turned to one side and the contact is held open by a catch. It is
put out of use by pressing the plunger to one side.

The matting shown in Fig. 245 is provided with spring contacts so
placed that no part may be stepped upon without sounding the alarm.
When placed in a doorway and properly connected with a signal, no
person can enter without starting an alarm. The matting is attached to
the alarm by the wires _C_ and contacts are set at close intervals so
that a footstep on the mat must close at least one contact.

=Annunciators.=--It is often convenient for a bell or buzzer to serve
two or more push buttons placed in different parts of the house. In
order that there may be means of designating the push button used--when
the bell is rung--an annunciator is provided. This is a box arranged
with an electric bell and the required number of pointers and fingers
corresponding to the push buttons. In Fig. 246 is shown an annunciator
with which two push buttons are served by the single bell. The
annunciator is placed at the most convenient place of observation,
usually in the kitchen. When the bell rings the pointer indicates the
push button that has last been used. In hotels or apartment houses
an annunciator with a single bell may thus serve any number of push
buttons. In a burglar-alarm system the annunciator numbers are arranged
to indicate the windows and other openings at which entrance might be
made. When the alarm sounds the annunciator indicates the place from
which the alarm is made.

=Table Pushes.=--Call bells to be rung from the dining-room table are
connected with an annunciator or to a separate bell. The table pushes
may be temporarily clamped on the edge of the table and connected by
a cord to an attachment set in the floor or the connection may be made
by a foot plate set on the floor. In Fig. 247 is shown a form of push
_P_ which is intended to be clamped to the edge of the table under the
cloth. The plate _F_ forms the floor connection. It is set permanently
with the upper edge flush with the surface of the floor. The part _S_,
in which the connecting cord terminates, when inserted in the floor
plate, makes contact at the points _C_ to form an electric circuit
with the battery. The foot plate shown in Fig. 248 is only an enlarged
push button which is set under the table in convenient positions to
be pressed with the foot. Its connection might be made as indicated
or with the same floor connection as that of the preceding figure.
Fig. 249 is a simpler form of floor push in which a metallic plug is
inserted in the floor plate. When the plug _R_ is pressed, contact is
made at the points _C_ to form the circuit with the battery and bell.

[Illustration: FIG. 246.--A kitchen annunciator.

FIG. 247.--Plug attachment and table push for a dining table.

FIG. 248.--Foot plate and contact for table bell.

FIG. 249.--Call bell attachment with detachable contact piece.]

=Bell-ringing Transformers.=--The general employment of alternating
electricity for all commercial service requiring distant transmission
is because of the possibility of changing the voltage to suit any
condition. The energy transmitted is determined by the amperes of
current carried by the wires and the volts of pressure by which it
is impelled. The product of these two factors determines the watts of
energy transmitted.

    110 volts × 1 ampere = 110 watts.

If the voltage is raised to say ten times the original intensity with
the same current, the quantity of energy is ten times the original

    1100 volts × 1 ampere = 1100 watts.

The carrying capacity of wires is determined by the amperes of current
that can be transmitted without heating.

The cost of copper wire is such that the expense of large wires for
carrying a large current is unnecessary where by raising the voltage a
small wire will perform the same service; therefore, it is desirable
to transmit electric energy at a high voltage and then transform it to
suit the condition of usage.

Alternating current may be transformed to a higher or a lower voltage
to suit any condition by using step-up or step-down transformers.

A transformer is a simple device composed of two coils of wire wound on
a closed core of iron. The coil into which is sent the inducing current
is the primary. That in which the current is induced is the secondary
coil. The change in voltage between primary and secondary coils vary as
the number of turns of wire which compose the coils. The house circuit
may be stepped down from the customary 110 volts to a voltage such as
is furnished by a single dry cell, or a battery of cells.

In principle, the action of the transformer is the same as that of
the induction coil, a detailed explanation of which will be found
in any text-book of physics. Each impulse of current in the primary
coil of the transformer magnetizes its core and the magnetism thus
excited induces a corresponding current in the secondary coil. Since
alternating current in the primary coil constantly changes the polarity
of the core, each change of magnetism induces current in the secondary

Small transformers are frequently used for operating doorbells,
annunciators, etc., in place of primary batteries. These transformers
are also used to supply current for lighting low-power tungsten lamps
that cannot be used with the ordinary voltages employed in house
lighting. The primary wires of the transformer are attached to the
service wires in the house and from the secondary wires voltages are
taken to suit the desired purposes.

[Illustration: FIG. 250.--Doorbell transformer.]

[Illustration: FIG. 251.--Details of doorbell transformer.]

Fig. 250 shows such a transformer with the cover partly broken away to
expose the interior construction. The wires from house mains _MM_ lead
the current to the primary coil _P_ which is a large number of turns
of fine wire wound about a soft-iron core. The induced current in the
secondary coil _S_ is taken from the contact points 1, 2, 3 and 4.
The construction of the transformer coils shown in Fig. 250 indicates
the primary wires at _LL_ of Fig. 251. The wires of the primary coil
are permanently attached to house wires. The reactive effect of the
magnetism in the coil permits only enough current to flow as will keep
the core excited. This is a step-down transformer and the secondary
coil contains fewer turns of wire than the primary coil. Since the
voltage induced in the secondary coil is determined by the number of
turns of wire in action, this coil is so arranged that circuits formed
by attachment with different contacts give a variety of voltages. The
numbers on the front of Fig. 250 correspond to those of Fig. 251. The
coils between contact 1 and the others 2, 3 and 4, represent different
number of turns of wire and in them is induced voltages corresponding
with the number of turns of wire in each.

=The Recording Wattmeter.=--To determine the amount of electricity used
by consumers, each circuit is provided with some form of wattmeter.
These meters might be more correctly called watt-hour meters since they
register the watt-hours of electrical energy that pass through the

[Illustration: FIG. 252.--Recording watt meter.]

In the common type of meter, the recording apparatus in composed of
a motor and a registering dial. The motor is intended to rotate at a
rate that is proportional to the amount of passing current. An example
of this device is the Thompson induction meter of Fig. 252. The motion
of the aluminum disc seen through the window in front indicates at any
time the rate at which electricity is being used. This constitutes
the rotating part of the motor. It is propelled by the magnetism,
created by the passing current, and is sensitive to every change that
takes place in the electric circuit. Each lamp, heater or motor that
is brought into use or turned off produces a change of current in the
conducting wires and this change is indicated by the rate of rotation
of the disc. Each rotation of the disc represents the passage of a
definite amount of electricity that is recorded on the registering

The shaft on which the disc is mounted is connected with the recording
mechanism by a screw which engages with the first of a train of gears.
These gears have, to each other, a ratio of 10 to 1; that is, ten
rotations of any right-hand gear, causes one rotation of the gear
next to the left. The pointers on the dial are attached to the gear
spindles. One rotation of the right-hand dial will move the pointer
next to the left one division on its dial. Each dial in succession will
move in like ratio.

The meters are carefully calibrated and usually record with
truthfulness the amount of electricity used. They are, however, subject
to derangement that produces incorrect registration.

=To Read the Meter.=--_First_, note carefully the unit in which the
dial of the meter reads. The figures above the dial circle indicate
the value of one complete revolution of the pointer in that circle.
Therefore, each division indicates one-tenth of the amount marked above
or below the circle.

_Second_, in reading, note the direction of rotation of the pointers.
Commencing at the right, the first pointer rotates in the direction of
the hands of a clock (clockwise); the second rotates counter-clockwise;
the third, clockwise; etc., alternately. The direction of rotation of
any one pointer may easily be determined by noting the direction of
the sequence of figures placed around each division. The arrows (shown
above) indicate the direction of rotation of the pointers when the
meter is in operation.

_Third_, read the figures indicated by the pointers from right to
left, setting down the figures as they are read, _i.e._, in a position
relative to the position of the pointers. NOTE: One revolution of
the first or right-hand pointer makes one-tenth of a revolution of
the pointer next to it on the left. One revolution of this second
pointer makes one-tenth of a revolution of the pointer next to it on
the left, etc. Therefore, if, when reading the dial, it is found that
the second pointer rests very nearly over one of the tenth divisions
and it is doubtful as to whether it has passed that mark, it is only
necessary to refer to the pointer next to it on the right. If this
pointer on the right has not completed its revolution, it shows that
the second pointer has not yet reached the division in question. If it
has completed its revolution, that is, passed the zero, it indicates
that the second pointer has reached the division and the figure
corresponding is to be set down for the reading.

[Illustration: FIG. 253_a_.--This dial reads 9484 kilowatt hours.]

The foregoing also applies to the remaining pointers. When it is
desired to know whether a pointer has passed a tenth division mark, it
is necessary to refer only to the next pointer to the right of it.

_Fourth_, see if the register is direct-reading, _i.e._, has no
multiplying constant. Some registers are not direct-reading in that
they require multiplying the dial reading by a constant such as 10
or 100 in order to obtain the true reading. If the register bears
some notation such as “Multiply by 100,” the reading as indicated by
the pointers should be multiplied by 10 or 100 as the case may be to
determine the true amount of energy consumed.

Some of the earlier forms of meters were equipped with what is known
as a “non-direct-reading register.” In this case, the reading must be
multiplied by the figure appearing on the dial as just explained, but
the dial differs from those just described in that the multiplying
constant is generally a fraction such as 1/2, etc., and the dial has
five pointers. This older style of register reads in “watt-hours” of

_Fifth_, the reading of the dial does not necessarily show the
watt-hours used during the past month. In other words, the pointers
do not always start from zero. To determine the number of watt-hours
used during a certain period it is necessary to read the dial at
the beginning of a period and again at the end of that period. By
subtracting the first reading from the second, the number of watt-hours
or kilowatt-hours used during the period is obtained.

The meter man, having in his possession a record of the readings
of each customer’s meter for the preceding months, is thus able to
determine the amount of energy consumed monthly.


Fig. 253_a_ shows an example of an ordinary dial reading. Commencing
at the first right-hand pointer, Fig. 253_c_, it is noted that the
last figure passed over by the pointer is 1. The next circle to the
left shows the figure last passed to be 2, bearing in mind that the
direction of the rotation of this pointer is counter-clockwise. The
last figure passed by the next pointer to the left is 1, while that
passed by the last pointer to the left is obviously 9. The reading to
be set down, therefore, is 9121.

[Illustration: FIG. 253_b_.--This dial reads 997 kilowatt hours.]

[Illustration: FIG. 253_c_.--This dial reads 9121 kilowatt hours.]

In a similar manner the dial shown in Fig. 253_b_ may be read. In
this case, however, three of the pointers rest nearly over the
divisions and care must be used to follow the direction to avoid
error. Commencing at the right, the first pointer indicates 7. The
second pointer has passed 9 and is approaching 0. The third pointer
appears to rest directly over 0, but since the second pointer reads
but 9, the third cannot have completed its revolution and hence the
figure last passed is set down which in this case is 9. Similarly,
the fourth or left-hand pointer appears to rest directly over 1 but
by referring to the pointer next to it on the right, we find that its
indication is 9 as just explained. Therefore, the fourth pointer cannot
have reached 1, and so the figure last passed which is 0 is set down,
which in this case is 9. Similarly, the fourth or left-hand pointer
appears to rest directly over 1, but by referring to the pointer next
to it on the right we find that its indication is 9 as just explained.
Therefore, the fourth pointer cannot have reached 1, and so we set down
the figure last passed which is 0. The figures as they have been set
down, therefore, are 0997, which indicates that 997 kilowatt-hours of
electricity have been used.

If, for example, the reading of this meter for the preceding month was
976 kilowatt-hours, the number of kilowatt-hours used during that month
would be 997-976 = 21 kilowatt-hours.

=State Regulation of Meter Service.=--Electric wattmeters are subject
to errors that may cause them to run either fast or slow. Complaints
made of inaccurate records or readings are usually rectified by the
electric company. In many States all public utilities are governed
by laws that are formulated by public utilities commissions or other
bodies from which may be obtained bulletins fully describing the
conditions required of public service corporations or owners of public
utilities. The following quotation from Bulletin No. V., 233 of the
Railroad Commission of Wisconsin, will give an illustration of the
requirement in that State.

     RULE 14.--CREEPING METERS.--No electric meter which registers
     upon “no load” shall be placed in service or allowed to remain in

This means that when no electricity is being used in the system the
motor disc should remain stationary and if it shows any motion under
such condition it is not recording accurately.


     RULE 17.--Each watt-hour meter shall be tested according to
     the following schedule and adjusted whenever it is found to
     be in error more than 1 per cent., the tests both before and
     after adjustment being made at approximately three-quarters and
     one-tenth of the rated capacity of the meter. Meters operated at
     low power-factor shall also be tested at approximately the minimum
     power-factor under which they will be required to operate. The
     tests shall be made by comparing the meter, while connected in
     its permanent position, on the consumer’s premises with approved,
     suitable standards, making at least two test runs at each load, of
     at least 30 seconds each, which agree within 1 per cent.

     Single-phase, induction-type meters having current capacities not
     exceeding 50 amperes shall be tested at least once every 4 months
     and as much oftener as the results obtained shall warrant.

     All single-phase induction-type meters having current capacities
     exceeding 50 amperes and all polyphase and commutator-type meters
     having voltage ratings not exceeding 250 volts and current
     capacities not exceeding 50 amperes shall be tested at least once
     every 12 months.

     All other watt-hour meters shall be tested at least once every 6

     RULE 20.--REQUEST TESTS.--Each utility furnishing metered electric
     service shall make a test of the accuracy of any electricity
     meter upon request of the consumer, provided the consumer does
     not request such test more frequently than once in 6 months. A
     report giving the results of each request test shall be made to
     the consumer and the complete, original record kept on file in the
     office of the utility.

=Electric Batteries.=--Electric batteries are composed of electric
cells that are made in two general types: the _primary cell_, in
which electricity is generated by the decomposition of zinc; and the
_secondary cell_ or storage cell in which electricity from a dynamo
may be accumulated and thus stored. Electric cells are the elements
of which electric batteries are made; a single electric cell is often
called a battery but the battery is really two or more cells combined
to produce effects that cannot be attained by a single element.

Both primary and secondary batteries form a part of the household
equipment but the work of the secondary battery is used more
particularly for electric lighting, the operation of small motors and
for other purposes where continuous current is required. It will,
therefore, be considered in another place.

Primary batteries are used to operate call-bells, table pushes,
buzzers, night latches and various other forms of electric alarms
besides which they are used in gas lighters, thermostat motors and
for many special forms, all of which form an important part in the
affairs of everyday life. Primary battery cells for household use
are made to be used in the wet and dry form, but the dry cell is now
more extensively used than any other kind and for most purposes has
supplanted the wet form.

Formerly all primary cells were made of zinc and copper plates placed
in a solution called an electrolite, that dissolved the zinc and thus
generated electricity, the electrolite acting as a conductor of the
electricity to the opposite plate. In later electric cells the copper
was replaced by plates of carbon and from the zinc and carbon cell was
finally evolved the present-day _dry cell_. When the use of electric
cells reached a point where portable batteries were required, a form
was demanded from which the solution could not be lost accidentally.
The first electric cells in which the electrolite was not fluid was,
therefore, called a dry cell. These cells are not completely dry. The
electrolite is made in the form of a paste that acts in the same manner
as the fluid electrolite and is only dry in that it is not fluid.

[Illustration: FIG. 254.--Electric dry cell.]

[Illustration: FIG. 255.--Details of electric dry cell.]

In construction the dry cell is shown in Figs. 254 and 255, the former
showing its exterior and the latter exposing its internal construction.
The container is a zinc can which is lined with porous paper to prevent
the filler from coming into contact with the zinc. The zinc further is
the active electrode, the chemical destruction of which generates the
electricity. The parts enclosed in the container are: a carbon rod,
which acts as the positive pole; and the filler, composed of finely
divided carbon mixed with manganese dioxide and wet with a solution of
salammoniac. The composition plug, made of coal-tar products and rosin,
is intended to keep the contents of the can in place and prevent the
evaporation of the moisture. Binding posts attached to the carbon rod
and soldered to the can furnish the + and-poles.

In the action of cell, the salammoniac attacks the zinc in which
chemical action electricity is evolved. The electricity is conducted
to the carbon pole through the carbon and the salammoniac solution
which in this case is the electrolite. In the dissolution of the
zinc, hydrogen gas is liberated which adds to the resistance of the
cell and thus reduces the current. The presence of the hydrogen is
increased when the action of the cell is rapid and the decrease in
current is said to be due to _polarization_. The manganese dioxide is
mixed with the filler in order that the free hydrogen may combine with
the oxide and thus reduce the resistance. This process is known as
_depolarization_. The combination between the hydrogen and the oxide
is slow and for this reason the depolarization of batteries sometimes
require several hours. Dry cells are usually contained in paper cartons
to prevent the surfaces from coming into contact and thus destroying
their electrical action.

The best cell is that which gives the greatest amount of current for
the longest time. Under any condition the working value of a cell
is determined by the number of amperes of current it can furnish.
The current is measured by a battery tester such as Fig. 257. The
+ connection of the tester is placed in contact with the + pole of
the cell or battery and the other connection placed on the-pole. The
pointer will immediately indicate the current given out by the battery.
A new dry cell will give 20 or more amperes of current for a short
time but if used continuously the quantity of current will be reduced
by polarizing until but a very small amount is generated. A cell that
indicates less than 5 amperes should be replaced. If short-circuited,
that is if the poles are connected without any intervening resistance,
a large amount of current will be given but the cell will soon wear
out and possibly be ruined. A cell should, therefore, never be allowed
to become short-circuited. The voltage of a cell is practically
continuous and should be from 1.5 to 1 volt. It is quite possible that
a cell may possess its normal voltage and yet deliver little current;
the voltage of a cell does not indicate its working property. In order
to be assured of active cells they should be tested at the time of
purchase with an ammeter.

The moisture in the paste of a cell is that which forms the circuit
between the zinc and the carbon elements. If the paste has dried out
its resistance is increased and the cell generates little current. The
voltage of such a cell may be normal while the amperage is very low.
Cells in this condition may be revived by adding moisture to the paste
as a temporary remedy. This may be accomplished by puncturing the can
with a nail and adding water. A solution of salammoniac may be used
instead of water and the cell soaked to accomplish the same purpose;
this, however, is only a temporary expedient.

Temperature influences the working properties of an electric cell in
pronounced manner. The moisture contained in the cell is composed of
ammonium chloride and zinc chloride and consequently the resistance
of the cell increases with the fall of temperature; the effect of the
resistance thus added is a decrease in the flow of current. Batteries
should be kept in a temperature as nearly as possible that of 70°F. The
battery regains its normal rate of discharge when the temperature is

The normal voltage and amperage for a given make of cell is practically
the same for all. The size of the cell does not in any way influence
the voltage. Small cells and large cells are the same. The large
cells are advantageous only in that they give out a greater number
of ampere-hours of energy. All batteries are rated in the number of
ampere-hours of current they are capable of furnishing. The ampere-hour
represents an ampere of current for one hour. On this basis all
batteries are rated for the total amount of energy they are capable
of producing. If the battery is worked at a high current, its life is
short; if however, it is discharged at a low rate, its life should be
long. In all cases the product of the number of amperes and the number
of hours constitute the ampere-hours of energy produced.

=Battery Formation.=--For ordinary household work as that of operating
doorbells, etc., the cells which form a battery are joined in series,
that is the positive or carbon pole of one cell is joined to the zinc
or negative pole of the next. The cells so connected are placed in
circuit with the bell and push button. If by accident the two cells of
a battery are joined with both carbon poles or both zinc poles together
the battery will give out no current because the voltage is opposed.

[Illustration: FIG. 256.--Battery combinations.]

In the use of batteries for ignition as for gasoline engines,
automobiles, etc., the arrangement of the cells has frequently
a decided influence on the effect produced. In Fig. 256 _A_ is
represented four cells joined in series, that is the carbon or + poles
are joined with the zinc or-poles, alternately. Connected in this
manner if each cell gives 1.5 volts the battery will give 4 × 1.5 = 6
volts; the current, however, will remain as that of a single cell. If
the cells singly give 20 amperes, the battery will give 20 amperes.
When cells are connected in this form the current passes through each
cell in turn and is as much a part of the circuit as the wires. Should
one of the cells be “dead”--that is delivering no current--it will act
as additional resistance and the current is reduced.

When joined in multiple or parallel connection as in Fig. 256 _B_, in
which all similar binding posts are connected, the effect is decidedly
different. In the multiple connection all of the zincs are joined to
act as a single zinc and all of the carbons are likewise joined and act
as a single carbon. In such a combination the voltage will be that of
a single cell 1.5 volts, but the amperage will be four times that of a
single cell or 80 amperes.

The diagrams and following descriptions of possible combinations were
taken from a bulletin on battery connections issued by the French
Battery and Carbon Co.

By combining the series and multiple connections, as shown in Fig.
_C_, both the voltage and current can be increased over that delivered
by one cell. Referring to the figure, it is seen that in each of the
two rows of four cells the cells are connected in series. This would
produce 6 volts and 20 amperes for the series of four which may now be
assumed as a unit, so that the two rows can be imagined as two large
cells, each of which has a normal output of 20 amperes at 6 volts. Now
by connecting the similar poles of two such large cells they are in
multiple and we get an increased current or 40 amperes and 6 volts,
which is the capacity of the eight cells connected as shown in the
figure. This is commonly designated as a _multiple-series_ battery.

Fig. 256 _D_ illustrates a multiple-series connection made in a
different manner, but which produces the same voltage and current as
the above mentioned. In Fig. _D_, two cells at a time are connected in
multiple, and these sets are then connected in series. The capacity of
each set of two is 40 amperes at 1-1/2 volts, and as these four sets
are connected in series the total output of the eight cells combined is
6 volts and 40 amperes, the same as that produced by the connections
shown in Fig. _C_.

Fig. _E_ shows the multiple-series connection illustrated in Fig. _D_,
applied to twelve cells in which four sets of three cells each are
wired in series, the three cells of a set being in multiple so that the
capacity of a set is 1-1/2 volts and 60 amperes. By connecting the
four sets in series as shown, the total capacity will be 60 amperes at
6 volts.

The use of the series-multiple connection is a distinct step forward
in dry-cell use. The arrangement of cells shown in Figs. _C_ or _D_ is
better than the arrangement in Fig. _A_, in just the same way that a
team of horses is better than a single horse. One horse pulling a load
of 2 tons may become exhausted in one hour, but two horses pulling that
same load may work continuously for six hours. It is true that in Fig.
_C_ there are twice as many cells used as in Fig. _A_, but the eight
cells in Fig. _C_ will do from three to four times as much work as
the four cells in Fig. _A_. In other words, while more cells are used
in the multiple-series arrangement, the amount of service per cell is
greater and the service is, therefore, cheaper in the multiple-series

Some battery manufacturers sell their batteries put up in boxes, the
cells being connected up in multiple-series and surrounded by pitch
or tar to keep out the moisture. This has certain advantages as well
as certain disadvantages. One of the objections to this method of
putting up dry cells is that if by any chance one cell out of the eight
or twelve which are buried in the pitch is defective it will run all
of the cells down, and being buried offers no means of detection or
removal. It is not possible to guarantee absolutely that a weak cell
will not be occasionally included in a large number, so dry cells may
be expected to vary to some degree among themselves.

It is interesting to know the effect of one weak cell on a
series-multiple arrangement. If, for example, in Fig. _C_ or Fig. _D_,
the dotted line connecting (_a_) and (_b_) be used to indicate a cell
which is partly short-circuited by internal weakness or external defect
the result is as follows:

In the arrangement shown in Fig. _C_, where one cell of the upper four
is short-circuited, the lower four will discharge through the upper
four even though the external circuit is not closed; that is, one
short-circuited cell will cause a run-down in all of the cells. In Fig.
_D_, however, one short-circuited cell will influence not the entire
set but the other one to which it is directly connected. There is thus
seen to be an advantage in the arrangement of Fig. _D_ and Fig. _E_,
over the arrangement in Fig. _C_.

In making connections between cells insulated wire should be used, or
special battery connectors are preferably employed. The ends of the
wires or connectors and the binding posts must be scraped clean so that
good electrical connection can be made between the two, and the knurled
nuts should be screwed tight into place. Care must also be taken that
the pasteboard covering around the battery is not torn. This would
allow contact between the zinc containers, and thus short-circuit the
cells. The batteries should be placed so that the zinc cans and the
binding posts of any cell do not come into contact with any other cell.
Vibration might cause enough motion for the brass terminal to wear
through the pasteboard of the neighboring cell and make contact with
the zinc can.

Different classes of work require different amounts of current at
different voltages and by choosing the proper combination of series,
multiple, or series-multiple connections practically every requirement
can be fulfilled. For electric bells, telegraph instruments, miniature
lights, toy motors with fine wire windings, etc., series connection is
recommended for the reason that the resistance of the external circuit
is high and a large voltage is necessary. For spark coils, magnets
and toy motors with large wire windings, multiple or series-multiple
connection of batteries should be used as a high voltage is not

For some work, gas-engine ignition especially, it is economical to have
two complete sets of batteries, either of which can be thrown into
the circuit at will, so that while one set is delivering current the
other is recuperating. It has been estimated that by using two sets of
batteries, properly connected to give the desired current, the life of
each set is increased about four times. Thus it is seen that a saving
of 50 per cent. is effected in the cost of the batteries.

=Battery Testers.=--The “strength” of a cell is determined by the
amperes of current it is capable of producing; therefore, a meter that
will indicate the amount of current being produced is used to test the
current strength of the cell. Battery testers are made to indicate
voltage or amperage and sometimes the instrument is made to indicate
both volts and amperes. As explained above, the voltage of a cell is
not a true indicator of its strength. The ampere meter or ammeter, as
it is termed, is the proper indicator of the strength of the cell.

[Illustration: FIG. 257.--Battery tester.]

The common battery tester does not always give the exact number of
amperes of current, but it indicates the relative strength which is
really the thing desired. When the current from an active cell is once
shown on the dial of the tester, any other cell of the same intensity
will be indicated in like amount.

=Electric Conductors.=--Covered wire for carrying electricity is made
in a great variety of forms and designated by names that have been
suggested by their use. These wires are made of a single strand or in
cables, where several wires are collected, insulated and formed into a
single piece. Cables may contain any number of insulated wires.

The sizes of wires are determined by a wire gage. In the United States
the B. & S. gage is used as the standard for all wires and sheet metal.
The gage originated with the Brown & Sharp Mfg. Co. of Providence,
R. I., and has become a national standard by common consent. The
numbers range from No. 0000 to No. 60. The size of wire for household
electrical service ranges from No. 18 which is 0.04 inch in diameter to
No. 8 which is 0.128 inch across. The carrying capacities in amperes of
wires, as given by the Underwriters’ table of sizes from No. 8 to No.
18, are as follows:

    | Wire |   Rubber    |    Other    |
    | gage | insulation, | insulation, |
    |  No. |   amperes   |   amperes   |
    |   8  |     35      |     50      |
    |  10  |     25      |     30      |
    |  12  |     20      |     25      |
    |  14  |     15      |     20      |
    |  16  |      6      |     10      |
    |  18  |      3      |      5      |

=Lamp Cord.=--The flexible cord used for drop lights, connectors,
portable lamps, extensions, etc., is made of two cords twisted together
or two cords laid parallel and covered with braided silk or cotton.
The conductors consist of a number of No. 30 B. & S. gage, unannealed
copper wires twisted into a cable of required capacity. The conductor
is wound with fine cotton thread over which is a layer of seamless
rubber, and the whole is covered with braided cotton or silk. Lamp
cord is sold in three grades, old code, new code, and commercial, which
vary only in the thickness and quality of rubber which encloses the

The new code lamp cord is identical with the old code form except that
it is required by the National Board of Fire Underwriters to be covered
with a higher quality of rubber insulation than was used in the old
form. The commercial cord is not recognized by the National Board of
Underwriters. It is practically the same as that described but does not
conform to the tests prescribed for the new code cord.

The sizes of the conductors enclosed in the lamp cord are made equal
in carrying capacity to the standard wire gage numbers. The sizes
ordinarily used are No. 18 and 20 gage but they are made in sizes from
No. 10 to No. 22 of the Brown & Sharp gage.

=Portable Cord.=--This is a term used to designate reinforced
lamp cord. The wires are laid parallel and are covered as with a
supplementary insulation of rubber. The additional insulation and the
braided covering assumes a cylindrical form. The covering is saturated
with weatherproof compound, waxed and polished.

=Annunciator Wire.=--This wire is made in the usual sizes and covered
with two layers of cotton thread saturated with a special wax and
highly polished. As the name implies it is used for annunciators, door
bells and other purposes of like importance.

=Private Electric Generating Plants.=--The conveniences to be derived
from the use of electricity were for many years available only by
those who lived in distributing areas covered by commercial electrical
generating plants. Except in towns of sufficient size to warrant the
erection of expensive light and power systems or along the lines of
electric power transmission, current for domestic purposes was not

Within a comparatively few years there have been developed a number
of small electric generating systems that are suitable for supplying
the average household with the electric energy for all domestic
conveniences. The combination of the gasoline engine, the electric
dynamo and the storage battery have made possible generating apparatus
that is operated with the minimum of difficulty and which supplies
all of the electric appliances that were formerly served only from
commercial electric circuits.

An electric generating system is commonly termed an electric plant.
It consists of an engine for the development of power, a dynamo
for changing the power into electricity and--to be of the greatest
service--a storage battery for the accumulation of a supply of energy
to be used at such times as are not convenient to keep the dynamo in
active operation.

Such a combination, each part comprised of mechanism with which
the average householder is unfamiliar, seems at first too great a
complication to put into successful practice. Such, however, is not the
case. The operation of small electric generating plants is no longer an
experiment. Their general use testifies to their successful service.
The working principles are in most cases those of elementary physics
combined with mechanism, the management of which is not difficult to
comprehend. Such plants are made to suit every condition of application
and at a cost that is condusive to general employment.

In a brief space it is not possible to enter into a detailed discussion
of the gasoline engine, the electric dynamo, and the storage battery
with the various appliances necessary for their operation; it is,
therefore, intended to give only a general description of the leading
features of each. The manufacturers of such plants furnish to their
customers and to others who are interested detailed information with
explicit instructions for their successful management.

The first private lighting plants were made up of parts built by
different manufacturers and assembled to form generating systems with
little regard to their adaptability. A gasoline engine belted to a
dynamo of the proper generating capacity supplied the electricity.
Neither the engines nor the dynamos were particularly suited to
the work to be performed, yet these combinations were sufficiently
successful to command a ready sale. The energy thus generated was
accumulated in a storage battery from which was taken the current for
a lighting and heating device. Besides the generating and storage
apparatus there is required in such a system, a switchboard, to which
are attached the necessary meters and switches that are required to
measure and direct the current to the various electric circuits.

Foresighted manufacturers, comprehending the probable future demand,
began the construction of the various parts, suited to the work and
the conditions under which they were to be employed. The manufacture of
apparatus, designed for the special service and composed of the fewest
possible parts, has reduced the operating difficulty to a point of
relative simplicity. Experience in the use of a large number of these
plants has revealed to the maker the course of many minor difficulties
of operation and the means of their correction. The mechanism has been
improved to prevent possible derangement and to simplify the means of
control, until the private electric plant is successfully employed by
those who have had no former experience with power-generating machines.

[Illustration: FIG. 258.--Household electric generating plant.]

As an example of the private electric plant Fig. 258 shows the
apparatus included in a combined engine, dynamo and switchboard,
connected with a storage battery. The relative size of the machine is
shown by comparison with the girl in the act of starting the motor.
This plant is of capacity suitable for supplying an average home with
electricity for all ordinary domestic uses. A nearer view of the
generating apparatus is given in Fig. 259 in which all of the exterior
parts are named. An interior view of the generating apparatus is
given in Fig. 260, in which is exposed all of the working parts. The
right-hand side of the picture shows all of the parts of the gasoline
engine that furnishes the power for driving the generator. This is
an example of an air-cooled gasoline engine in which the excess heat
developed in the cylinder is carried away by a drought of air. The air
draft is induced by the flywheel of the engine, which is constructed as
a fan. The blades of the fan, when in motion, are so set as to draw air
into the top of the engine casing and exhaust it from the rim of the
wheel. The air in passing takes up the heat in excess of that necessary
for the proper cylinder temperature. This form of cylinder cooling
takes the place of the customary water circulation and thus eliminates
its attending sources of trouble. In principle the engine is the same
as is employed in automobiles and other power generation.

[Illustration: FIG. 259.--Combined motor, electric generator and

On the left-hand side is seen the dynamo and switchboard. The
dynamo armature is attached to the crankshaft of the engine by which
it is rotated in a magnetic field to produce the desired amount of
electricity. The brushes, in contact with the commutator, conduct the
electricity as it is generated in the armature, which after passing
through the switchboard is made available from the two wires at the top
of the board marked “light and power wires.” These wires are connected
with the storage battery and also to the house circuits through which
the current is to be sent.

[Illustration: FIG. 260.--Details of motor, electric generator and

Referring to the switchboard of Fig. 259, the three switches and the
ammeter comprise the necessary accessories. The starting switch is
so arranged that by pressing the lever a current of electricity from
the storage battery is sent through the dynamo. The dynamo acting as
a motor starts the engine. When the engine has attained its proper
speed its function as a dynamo overcomes the current pressure from the
battery and sends electricity into the cells to restore the expended
energy, or if so desired the current may be used directly from the
dynamo for any household purpose. The box enclosing the switch
contains a magnetic circuit-breaker so constructed that when the
battery is completely charged the switch automatically releases its
contact and stops the engine.

The “stopping switch” at the right of the board and the “switch for
light and circuit” on the left are used respectively for stopping the
engine and for opening and closing the house circuits.

The meter performs a multiple function, in that it shows at any time
the condition of charge in the storage battery, the rate at which
current is entering or leaving the battery and also acts to stop the
engine when the battery is charged. At any time the pointer reaches the
mark indicated in the picture, the ignition circuit is automatically
broken and the engine stops. The fuses on the board in this case
perform the same function as those already described.

=Storage Batteries.=--These batteries have already been mentioned as
secondary batteries. They are sometimes called electric accumulators.
The electricity is stored or accumulated, not by reason of the
destruction of an electrode as in the primary cell but by the chemical
change that takes place in the plates as the charging current is sent
through the cell. When the battery is discharged, the current from the
dynamo is sent through the battery circuit in the reverse direction to
that of the discharge and the plates are restored to their original
condition. The action that takes place in charging and discharging is
due to chemical changes that take place in the plates and also in the
solution or electrolyte in which the plates are immersed.

There are two types of storage batteries, those made of lead plates
immersed in an acid electrolyte and the Edison battery which is
composed of iron-nickel cells immersed in a caustic potash electrolyte.
The former type is most commonly used and is the one to be described.

The lead-plate cell illustrated in Fig. 262 shows all of the parts of
a working element. The plates are made in the form of lead grids which
when filled to suit the requirements of their action, form the positive
and negative electrodes. The negative plates are filled with finely
divided metallic lead which when charged are slate gray in color. The
positive plates are filled with lead oxide. When charged they are
chocolate brown in color. In the figure there are three positive and
four negative plates which together form the element, then with their
separators are placed in a solution of sulphuric acid electrolyte. The
separators are thin pieces of wood and perforated rubber plates that
keep the positive and negative plates from touching each other and keep
in place the disintegration produced by the electro-chemical action of
the cell.

The unit of electric capacity in batteries is the ampere-hour. The
cell illustrated will accumulate 80 ampere-hours of energy. It will
discharge an ampere of current for 80 hours. If desired it may be
discharged at the rate of two amperes for 40 hours, or four amperes
for 20 hours, or at any other rate of amperes and hours, the product
of which is 80. The number of ampere-hours a cell will accumulate will
depend on the area of the positive and negative plates; large cells
will store a greater number of ampere-hours than those of small size.

The cells, no matter what size, give an average electric pressure of 2

The plates are joined by heavy plate-straps connecting all of the
positives on one end and all of the negative kind on the opposite end.
To insure rigidity the two sets are secured to the rubber cover by
locknuts. In this cell the plates are suspended from the cover. The
plate terminals are made of heavy lead connectors that when formed into
a battery are joined together with lead bolts and nuts.

[Illustration: FIG. 261.--Hydrometer for testing storage battery

The electrolyte is a solution of pure sulphuric acid in distilled water
and on its purity depends, in a great measure, its action and length of
life. The electrolyte is made of a definite density which is expressed
as its specific gravity. When fully charged the electrolyte will test
1220 by the hydrometer. That is, it will be 1.220 heavier than water.
When discharged it will test by the hydrometer 1185. This means that in
discharging the density has been reduced to 1.185 that of water. The
chemical change in the electrolyte is, therefore, an important part of
the charge and discharge of the cell. The density of an electrolyte
may be determined by a hydrometer such as Fig. 261. This is an ordinary
glass hydrometer such as is used for determining the density of fluids,
enclosed in a glass tube, to which is attached a rubber bulb. The point
of the tube is inserted into the opening at the top of the cell and the
electrolyte drawn into the tube by the reopening of the collapsed bulb.
The density is then read from the stem of the hydrometer.

=The Pilot Cell.=--In order to make apparent this density of the
electrolyte without the necessity of its measurement with a hydrometer,
one cell of the battery is provided with a gage as that of Fig. 262.
This is an enlargement of the end of the jar in which floats a hollow
glass ball of such weight that it will at any time indicate by its
position the relative density of the solution. When the cell is charged
the ball stands at the top of the gage and indicates a density 1220;
when discharged it is at the bottom and expressed by its position a
density of 1185. The electrolyte densities are the indicators of the
conditions of charge. The ball by its position shows at a glance the
quantity of electricity in the battery.

The voltage usually employed in household electric plants is that
of a battery composed of 16 cells. Since the normal voltage of a
storage cell is 2 volts such a battery joined in series is 32 volts.
This voltage for the purpose fulfills all ordinary conditions and is
generally employed. A battery of 16 cells, of 80-ampere-hour capacity,
will deliver current of 1 ampere for 80 hours at 32 volts intensity.
A 20-watt lamp on a 32-volt circuit requires 2/3 ampere for its
operation. The battery will, therefore, keep lighted one such lamp for
96 hours, or four 20-watt lamps may be lighted continuously for 24
hours, or eight lamps for 12 hours, before recharging.

Aside from its ability to supply the required light for the average
home, it furnishes energy sufficient for heating a flat-iron or other
heating apparatus, to operate motors for pumping water, driving a
washing machine or any other of the domestic requirements.

Such plants are made in sizes to suit any condition of requirement.
In large establishments a larger motor generator and battery will be
necessary with which to generate and store the required electricity
but in any case suitable apparatus is to be obtained to meet any
requirement of light, heat or power developed.

[Illustration: FIG. 262.--Electric storage cell.]

=National Electrical Code.=--The details governing the size, the
manner of placing and securing wires in buildings is included in the
regulations published by the National Board of Fire Underwriters as the
National Electric Code. Likewise the mechanical construction of all
apparatus dealing with electric distribution is definitely specified
so that manufacturers furnish reliable materials for all requirements.
In the specifications for furnishing buildings with the use of
electricity, descriptions are made of the desired types and styles of
the switches and various other fixtures to suit the requirements.

=Electric Light Wiring.=--In the equipment of a house for the use of
electricity, the wiring, together with distributing panel, the various
outlets, receptacles, switches, and other appliances that make up the
system, is of more than passing consequence. In the construction of the
electric system it is important that the wires and their installation
be done in a manner to meet every contingency.

The following descriptions for electric house wiring were taken from a
set of specifications published by the Bryant Electric Co. as applying
to buildings of wood frame construction. The specifications serve as
explanations for the appliances required in an ordinary dwelling. The
specifications are for the least expensive form of good practice in
wiring for frame buildings. They would not be permitted in large cities
where further protection from fire is required and where more rigid
rules are demanded by the Board of Fire Underwriters.

     1. SYSTEM.--The circuit wiring shall be installed as a two-wire
     direct current or alternating system. Not more than 16 outlets
     or a maximum of 660 watts shall be placed on any one circuit,
     allowing 110 watts for each baseboard plug connection or extension
     outlet and 55 watts for each 16 candlepower lamp indicated at the
     various wall and ceiling outlets on plans. All wiring shall be
     installed as a concealed knob-and-tube system.

The type of wiring is designated as a two-wire direct or alternating
current system in order that there shall be no doubt as to the method
of wiring to be used. There are other methods that might be employed
that need not be discussed here.

The 16 outlets mentioned are intended to cover all lamps or plug
attachments that are to be used for heaters, fans, motors, or any other
electric device. The 660 watts at 110 volts pressure will require 6
amperes in the main wires of the circuit, which is the maximum current
the wires are intended to carry. This does not mean that 110-watt lamps
might not be used but that no single circuit shall carry lamps that
will aggregate more than 660 watts.

The concealed knob-and-tube system mentioned is illustrated in Figs.
263 and 264, in which the wires which pass through joists and studding
are to be insulated by porcelain tubes and those wires which lay
parallel to these members are to be fastened to porcelain knobs which
are secured by screws to the wood pieces to prevent any possibility of
coming into contact with electric conducting materials.

[Illustration: FIG. 263.--Manner of securing wires by the knob-and-tube
system for ceiling outlets.]

     2. OUTLETS.--At each and every switch, wall, ceiling, receptacle
     or other outlet shown on plans, install a metal outlet box of a
     style most suitable for the purpose of the outlet. All outlet
     boxes must be rigidly secured in place by approved method and
     those intended for fixtures shall be provided with a fixture stud,
     or in the case of large fixtures, a hanger to furnish support
     independent of the outlet box.

=Outlet Boxes.=--For the safe and convenient accommodation of
switches, receptacles or other connections in the walls and ceilings
of a building, outlet boxes are used as a means of securing the wire
terminals to the receptacles. These boxes are made in a number of forms
for general application. One style is shown in Fig. 265. The boxes are
made of sheet steel and arranged to be secured in place with screws.
The box is further provided with screw fastenings to which the switch
or receptacle may be firmly attached.

[Illustration: FIG. 264.--This shows the knob-and-tube system of
securing the wires in partitions and the manner of fastening metal “cut
out” boxes; for switch, attachments, plugs, etc.]

     3. INSTALLATION OF WIRES, ETC.--All wires shall be rigidly
     supported on porcelain insulators which separate the wire at
     least 1 inch from the surface wired over. Wires passing through
     floors, studding, etc., shall be protected with porcelain tubes,
     and where wires pass vertically through bottom plates, bridging,
     etc., of partitions, an extra tube shall be used to protect wires
     from plaster droppings. Wires must be supported at least every 4
     feet and where near gas or water pipes extra supports shall be
     used. All porcelain material shall be non-absorptive and broken
     or damaged pieces must be replaced. Tubes shall be of sufficient
     length to bush entire length of hole. At outlets the wires shall
     be protected by flexible tubing, the same to be continuous from
     nearest wire support to inside of outlet box. Wires installed in
     masonry work shall be protected by approved rigid iron conduit
     which shall be continuous from outlet to outlet.

The method and reasons for supporting the wires described above are
as have already been mentioned under item 1. The reason for extra
supports near gas pipes and water pipes is as a precaution against the
possibility of short-circuiting.

[Illustration: FIG. 265.--Outlet box.]

     4. CONDUCTORS.--Conductors shall be continuous from outlet to
     outlet and no splices shall be made except in outlet boxes. No
     wire smaller than No. 14 B. & S. gage shall be used and for all
     circuits of 100 feet or longer, No. 12, B. & S. gage or larger
     shall be used. All conductors of No. 8 B. & S. gage or larger
     shall be stranded. Wires shall be of sufficient length at outlets
     to make connection to apparatus without straining connections.
     Splices shall be made both mechanically and electrically perfect,
     and the proper thickness of rubber and friction tape shall be then

Continuous conductors are required because of the possibility of
defects in the joints of spliced wire.

     5. POSITION OF OUTLETS.--Unless otherwise indicated or directed,
     plug receptacles shall be located just above baseboard; wall
     brackets, 5 feet above finished floor in bedrooms, and 5 feet 6
     inches in all other rooms; wall switches, 4 feet above finished
     floors. All outlets shall be centered with regard to panelling,
     furring, trim, etc., and any outlet which is improperly located on
     account of above conditions must be corrected at the contractor’s
     expense. All outlets must be set plumb and extend to finish of
     wall, ceiling or floor, as the case may be, without projecting
     beyond same.

     6. MATERIALS.--All materials used in carrying out these
     specifications shall be acceptable to the National Board of Fire
     Underwriters and to the local department having jurisdiction.
     Where the make or brand is specified or where the expression
     “equal to” is used, the contractor must notify the architect of
     the make or brand to be used and receive his approval before any
     of said material is installed. Where a particular brand or make is
     distinctly specified, no substitution will be permitted.

     7. GRADE OF WIRE.--The insulation of all conductors shall be
     rubber, with protecting braids, which shall be N.E.C. Standard
     (National Electrical Code Standard).

     8. OUTLET BOXES.--Outlet boxes shall be standard pressed steel,
     knock-out type and shall be enameled.

     9. LOCAL SWITCHES.--Local wall switches shall be two-button flush
     type completely enclosed in a box of non-breakable insulating
     material with brass beveled-edge cover plate finished to match
     surrounding hardware.

Fig. 269 shows the various forms and grades of switches that there are
on the market. The screws which attach the plate to the switch enter
bushings that are under spring tension thereby preventing defacement
of the plate by overtightening of the screws. Single-pole is to be
used where the load will not be in excess of 660 watts; double-pole to
be used where the load is more then 660 watts or where for any other
reason it is desirable to break the current at both wires. Three-point
switches are to be used when a light or group of lights is to be
controlled, as hall lights that may be lighted or extinguished, from
either the top or at the bottom of a stairway. Four-point switches are
to be used between and two, three-point switches to control additional
lights. Where two or more switches are placed together an approved gang
plate is to be provided which designates the use of each switch. Where
indicated on the plan, clothes closets shall be equipped with automatic
door switch to connect the light when the door is open.

     10. PILOT LIGHTS.--Switches controlling cellar, attic and porch
     lights shall have pilot lamp in parallel on the load side of the
     switch. The switch in Fig. 3 requires for its installation a
     two-gang outlet box. The ruby bull’s-eye which covers the lamp is
     practically flush, extending from the wall no further than the
     buttons of the switch.

Pilot lights are intended to indicate the operation of other lights or
apparatus that cannot be directly observed.

The term bull’s-eye applies to a colored-glass button covering a
miniature lamp which burns whenever a light is used which is apt to be
forgotten and allowed to burn for a longer time than necessary.

     11. PLUG RECEPTACLES.--Plug receptacles shall be of the
     disappearing-door type, with beveled-edge brass cover plate
     finished to match surrounding hardware (see Fig. 266). In this
     receptacle the doors are pushed inward by the insertion of the
     plug and upon its withdrawal close automatically, effectually
     excluding dirt and concealing the live terminals. It is the latest
     and best plug receptacle obtainable.

Plug receptacles are the attachments for the terminal pieces of plugs,
which temporarily connect portable lamps, electric fans or other
devices, they are made in many forms.

     12. WALL AND CEILING SOCKETS.--One-light ceiling receptacles shall
     be of a type to fit standard 3-1/4-inch or 4-inch outlet boxes.
     Wall sockets shall be of the insulated base type. Sockets in
     cellars shall be made entirely of porcelain and of the pull type.
     All lamp sockets used in fulfilling these specifications shall
     have an approved rating of 660 watts, 250 volts.

     13. DROP LIGHTS.--Drop lights shall consist of the necessary
     length of reinforced cord supported by an insulated rosette
     with brass base and cover; the latter to cover 4-inch outlet
     box, and furnished with a key socket complete with a 2-1/4-inch
     shade-holder. Each drop cord shall have an adjuster.

     14. HEATER SWITCH, PILOT AND RECEPTACLE.--Heating device outlets
     shall be equipped with combination of switch, pilot light and
     receptacle with plug and spare pilot lamp.

     15. SERVICE SWITCH.--The service-entrance switch shall be 30
     amperes, porcelain base with connections for plug fuses.

     INSTALLATION OF SERVICE SWITCH.--Service switch shall be installed
     in a moisture-proof metal box with hinged door.

     PANEL CABINET.--The distributing panel cabinet shall be of steel
     not less than No. 12 gage reinforced with angle iron frames, which
     shall be securely riveted in place. Cabinet shall be larger than
     panel to give at least 4-inch wire space around panel and shall be
     given at least two coats of moisture-repellant paint.

     DISTRIBUTING PANEL.--The distributing panel shall consist of
     two-wire 125-volt branch cutouts, two-wire 125-volt porcelain-base
     panel-board units, two-wire 125-volt porcelain-base deadfront
     panel-board units. The distributing panel shall be surrounded with
     an ebony asbestos or slate partition 1/2 inch thick which will
     form a wire space around panel.

     FUSES.--All fuses for branch circuits shall be not more than 10
     amperes capacity. The contractor shall furnish the owner with
     150 per cent. of required number of 125-volt plug-type fuses for
     complete installation.

     PANEL TRIM AND DOOR.--The panel trim and door shall be of steel,
     with brass cylinder lock and concealed hinges, all furnished under
     this contract. A directory of circuits and outlets served by panel
     shall be enclosed in glass with metal frame, mounted on inside of
     panel door.

     HARDWARE.--All hardware furnished under this contract shall match
     in quality and finish other adjacent hardware.

     THREE-WAY CONTROL.--The nearest outlet at top and bottom of all
     stairs and in entrance hall shall be controlled by three-way
     switches located on separate floors where directed.

     ELECTROLIER CONTROL.--Wherever there are ceiling outlets for
     fixtures having three or more sockets controlled by wall switches
     three wires shall be run between the switch box and the outlet to
     permit the use of electrolier switches.

     DINING-ROOM CIRCUIT.--Furnish and install in dining-room, where
     indicated on plans, an approved floor box containing an approved
     25-ampere plug receptacle. The wires connecting this receptacle to
     the center of distribution shall be No. 10 B. & S. gage. Furnish
     and deliver to whom directed an approved multiple-connection block
     consisting of three individually fused plug receptacles. The
     connection between the plug receptacle and this block shall be
     made by means of 10 feet of No. 10 B. & S. approved silk-covered
     portable cord with an approved 20-ampere cord connector 2 feet
     from the multiple block.

     HOUSE FEEDERS.--The size of the feeder from the service switch to
     the panel board shall be figured in accordance with the National
     Code rules for carrying capacity, allowing for all circuits being
     fully loaded. The feeder shall be of sufficient size, however, to
     confine the drop in voltage with all lights in circuit to 1 per
     cent. of the line voltage.

     SERVICE CONNECTION.--Make extension of house feeder overhead to
     lighting company’s mains and make all connections complete to the
     satisfaction of the light company and the architect. Furnish and
     install the necessary frame or backboard for meter.

     CALL BELLS.--The contractor shall furnish, install and connect
     all push buttons, bells, buzzers and annunciators, as shown on
     plans or therein described. All wiring shall be cleated in joists,
     studs, etc., with insulated staples. Damp places, metal pipes of
     all descriptions, flues, etc., must be avoided and wire fastenings
     must be applied in such a way that insulation is not damaged. No
     splices shall be made where same will not be accessible at any
     time after completion of building. Wires shall not be smaller than
     No. 18 B. & S. gage and shall be damp-proof insulated. Bells,
     buzzers, buttons, etc., shall be of approved make. Push button
     for main entrance door shall be provided with ornamental place
     with approved finish. Push button in dining-room shall consist of
     combination floor push, with necessary length of flexible cord and
     approved portable foot push. Furnish and install where directed
     three cells of carbon cylinder battery in a substantial cabinet.

     BURGLAR ALARM.--Furnish and install complete burglar alarm
     system consisting of the necessary wires, window springs, door
     springs, night latch cutout for front door, bell, batteries,
     cabinet, interconnection strip, etc., and everything required
     for a complete open-circuit system. Each window sash and door
     throughout the building shall be equipped with contact spring of
     approved make and all springs on same side of building on each
     floor shall be wired on one circuit and terminated on single-pole
     knife switch on interconnection strip. The interconnection strip
     shall be located as directed and shall have cutout switches for
     each circuit as well as a double-pole battery switch. The battery
     shall consist of at least three dry cells in suitable cabinet
     placed where directed and both positive and negative leads shall
     be carried direct to interconnection strip. The burglar-alarm
     wires shall be not less than No. 16 B. & S. gage, insulated and
     installed as specified for call bells.

     INTERCOMMUNICATING TELEPHONES.--Furnish and install an
     intercommunicating telephone system complete with all telephone
     sets, wiring, batteries, etc. All wires to be cables containing
     one pair of No. 22 B. & S. gage conductors for each station and
     a pair of No. 16 B. & S. gage conductors for talking and ringing
     battery respectively. Each pair of wires shall be twisted and all
     pairs shall be twisted around each other to eliminate cross talk
     and inductive noises. The wires shall be silk insulated, with a
     moisture repellent of beeswax or varnish and the whole covered
     with a lead sheath at least 1/64 inch in thickness. Where cables
     terminate in outlet boxes they shall be fanned out and laced in
     an orderly manner and secured to connecting terminals, one of
     which shall be provided for each wire. Install where directed in
     an approved cabinet at least four cells of dry battery each, for
     talking and ringing purposes.

     INSTALLATION OF INTERPHONE CABLE.--Intercommunicating cables shall
     be supported with pipe straps and liberal clearance shall be
     observed where near steam or other pipes.

=Automatic Door Switch.=--Where indicated on the plan, clothes closets
shall be equipped with automatic door switch to connect the light when
the door is open.

Fig. 266 is placed in the door frame in such position that electric
contact is made by release of the projecting pin as the door is
opened. When the door is closed, the pin is depressed and the light is

=Plug Receptacles.=--Plug receptacles shall be selected from the styles
shown in Figs. 267,_a_, _b_, _c_ or _d_.

[Illustration: FIG. 266.--Automatic door switch.]

Fig. 267,_a_ is the disappearing-door type with beveled-edge brass
cover plate finished to match surrounding hardware. In this receptacle
the doors are pushed inward by the insertion of the plug and upon
its withdrawal close automatically, effectually excluding dirt
and concealing the live terminals. It is the latest and best plug
receptacle obtainable.

Fig. 267,_b_ is of the Chapman type with beveled-edge brass cover plate
finished to match surrounding hardware. In this receptacle the doors
open outward but are flush whether the plug is in or out.

[Illustration: FIG. 267.--Styles of plug receptacles.]

[Illustration: FIG. 268.--Heating-device receptacles.]

Fig. 267,_c_ is of the screw-plug type with beveled-edge brass cover
plate finished to match surrounding hardware. By many this is
preferred for apartment use as it will receive any style of Edison
attachment plug.

[Illustration: FIG. 269.--Service switches.]

Fig. 267,_d_ is of the removable-mechanism type with beveled-edge brass
cover plate finished to match surrounding hardware. The mechanism of
this receptacle is exchangeable with the mechanism of the double-pole
switch as shown in Fig. 270,_c_.

=Heater Switch, Pilot and Receptacle.=--Heating-device outlets shall be
equipped with combination of switch, pilot light and receptacle with
plug and spare pilot lamp. Figs. 268,_a_, _b_, _c_ and _d_, represent
various forms from which selection may be made. All are adapted for the
same purpose and differ only in mechanical arrangement.

[Illustration: FIG. 270.--Local wall switches.]

=Service Switch.=--The service entrance switch may be selected from the
three styles shown in Figs. 269,_a_, _b_, and _c_.

[Illustration: FIG. 271.--Pilot lights.]

[Illustration: FIG. 272.--Wall and ceiling sockets.]

Fig. 269,_a_ is composed of a 30-ampere porcelain base with connections
for plug fuses.

Fig. 269,_b_ is a slate base with connections for cartridge fuses.

Fig. 269,_c_ is a slate base with connections for open-link fuses

=Local Switches.=--Local wall switches may be selected from the various
styles shown in Figs. 270,_a_, _b_, _c_, _d_ and _e_.

Fig. 270,_a_ is the two-button flush type completely enclosed in a box
of non-breakable insulating material with brass beveled cover plate
finished to match surrounding hardware.

[Illustration: FIG. 273.--Drop-light attachments and lamp bases.]

Fig. 270,_b_ is a two-button flush type with brass beveled-edge cover
plate finished to match surrounding hardware.

Fig. 270,_c_ is of the removable-mechanism type with brass beveled-edge
cover plate finished to match surrounding hardware.

Fig. 270,_d_ is the single-button flush type with brass beveled-edge
cover plate finished to match surrounding hardware.

Fig. 270,_e_ is the rotary-flush type with brass beveled-edge cover
plate finished to match surrounding hardware.

=Pilot Lights.=--Switches controlling cellar, attic and porch lights
may be either Fig. 270,_a_ or _b_.

Fig. 270,_a_ requires for its installation a two-gang outlet box. The
ruby bull’s-eye which covers the lamp is practically flush, extending
from the wall no further than the buttons of the switch.

Fig. 270,_b_ is installed in a single-gang box. The lamp extends
through the plate and is protected by a perforated cage which extends
about an inch from the plate.

=Wall and Ceiling Sockets.=--One-light ceiling receptacles may be
selected from the types shown in Figs. 272,_a_, _b_, _c_, _d_ and _e_.

Fig. 272,_a_ is of a type to fit standard 3-1/4-inch or 4-inch outlet

Fig. 272,_b_ is of the small concealed-base type.

Fig. 272,_c_ is of the large concealed-base type.

Fig. 272,_d_ is of the insulated-base type.

Fig. 272,_e_ is of the porcelain-base type.

Sockets in cellars shall be made entirely of porcelain. Those in
bathrooms shall be entirely of porcelain and of the pull type.

=Drop Lights.=--Drop lights shall consist of the necessary length of
reinforced cord supported by either brass or porcelain bases. Each drop
cord to have an adjuster. Figs. 273,_a_, _b_, _c_, _d_, _e_, _f_, _g_,
illustrate the various styles. Fig. 273,_h_ is a shade holder to be
used with the drop lights.



    Acetylene, gas burner, 302
      gas machine, the Colt, 300
        machines, 295
      generators, types of, 297
      stoves, 304

    Air conditioning, 240
      cooling plants, 244
      discharged by a flue, 225
      eliminators, 35, 36
      properties of, table, 199
      tester, the Wolpert, 233
      valves, 19

    Alcohol, sad irons, 289
      table stoves, 293

    Annunciators, 346

    Anthracite, graphitic, 186

    Atmospheric humidity, 196


    Backventing, of plumbing, 105

    Bathroom, 97

    Bathtubs, 98
      fixtures for, 100

    Bibb, compression flange, 89
      flange, 89
      Fuller, 89
      hose, 89
      lever handle, 90
      screw, 89
      self-closing, 90
      solder, 89
      wash-tray, 91

    Boiler, at end of season, 79
      cast-iron, 19, 20, 38
      cylindrical form of, 38
      house heating, 19, 24
      rules for management of, 77
      sheet-metal, 19

    Boiler, steam, rules for management of, 78
      the house-heating steam, 19

    Boyle’s law, definition, 161, 272

    Briquettes, 189

    British thermal units, 4
      for one cent, 190

    B.t.u., 2, 32, 182, 185

    Burglar alarms, 344

    Buzzers, 344


    Candle, foot, 313
      Hefner, 310
      power, 310
        horizontal, 310
        spherical, 311

    Cellar drain, 84

    Cell, Pilot, storage battery, 370

    Cesspools, 169

    Charcoal, 188

    Check-draft damper, 24

    Chimney flue, the right, 79

    Chimneys, “smokey,” 80, 81

    Cisterns, filters for, 152, 153
      galvanized iron tanks as, 152
      rain-water, 151
      wooden, 152

    Clinkers, 72, 73

    Close-nipples, 28

    Coal, 182
      anthracite or hard, 183, 193
      bituminous or soft, 184
      burning soft, 75
      calorific value of typical American, 192, 193
      cannel, 186
      coking, 184
      comparative value of, 189
      free burning, 75

    Coal, fusing-coking, 75
      grades of soft, 184
      pea size, 76
      price of, 190, 191
      semi-bituminous, 186, 193

    Cocks, basin, 92
      bibb, 88
      corporation, 87
      curb, 87
      Fuller, 91
        bibb, 89
        repairs for, 91
      pantry, 93
      sill, 93
      stop and drain, 88
      stop and waste, 87

    Code, national electric, 371

    Coke, 76, 188
      gas, 188

    Column, the water, 22

    Condensation, water of, 6, 10, 11, 15, 35

    Conductors, 374

    Cord, lamp, 363
      portable, 363

    Current, alternating, 332
      direct, 332


    Damper, ash-pit, 59
      check-draft, 24, 67, 69, 70
      direct-draft, 59, 61, 67
      regulator, 59, 60
        combined thermostat and, 67
        for hot-water furnaces, 61, 62
        for steam boiler, 60, 78

    Design, heating plant, 44

    Devining rod, 137

    Dew-point, 209
      to determine the, 212

    Dim-a-lite, 323

    Door bells, 342

    Draft, economy of good furnace, 70
      hand, regulation, 59
      induced, 69

    Drip-cock, 23

    Dry cells, 354


    Electric annunciators, 346
      batteries, 354
      battery formation, 358
        testers, 360
      burglar alarms, 344
      buzzers, 344
      conductors, 362
      door bell, 342
      dry cell, 355
      flat-iron, 326
      fuse plugs, 334, 337
      generating plants, 363
      heaters, 338
      heating devices, 305
      lamp cord, 362
      lamps, Gem, 306
        incandescent, 306
      motors, 332
      panel, 336
      range, 340
      signals, 341
      stoves, 339
      table pushes, 346
      toaster, 330

    Electrical measurements, units of, 317

    Electricity, 305

    Eliminator, air, 35, 36

    Evaporation as a cooling agent, 243


    Filaments, carbon, 308
      incandescent lamp, 306, 307
      tungsten, 307

    Fire-box, 19, 20, 54

    Firing, first day, 73
      in moderate weather, 74
      in severe weather, 74
      night, 72

    Fixtures, bathroom, 105
      kitchen and laundry, 94

    Flat-iron, electric, 326

    Flues, furnace, 55

    Flush tanks, 110
      details of construction, 112, 113
      low down, 111

    Foot-candle, 313

    Frost prediction, 212

    Fuels, comparative value of coal to other, 189
      danger from gaseous and liquid, 294
      heating values of domestic, 252
      moisture in, 194

    Furnace, cast-iron, 54
      firing, general rules for, 70
        times of day for, 72
      location of, 54
      the hot-air, 51, 52
        construction of, 52

    Furnace-gas leaks, 54

    Fuse plugs, 334


    Gage, Bourdon type of, 23
      electrified Bourdon spring pressure, 36
      glass, 22, 40, 161, 162
      steam, 22
      water, 22

    Gas, acetylene, machines, 295
      all-oil water, 251
      Blau, 251
      burner, Bunsen, 275
        open-flame, 278
      coal, 250
      lamps, mantle, 274, 276, 277
      lighters, 302
      measurements of, 253
      meter dials, reading of, 255, 256
      meters, 254
        prepayment, 256
      Pintsch, 251
      service rules, 256, 257
      ranges, 258
      water, 251

    Gases, heating values of, 252

    Gasoline, 250
      Beaumé test of, 261

    Gasoline, boulevard lamp, 287
      central generator plants for use of, 282
      cold process system of lighting with, 264, 265
      gas lamps, 286
      gravity test of, 262
      hollow-wire system of lighting and heating with, 269
      lamps, inverted mantle, 279
        portable, 280, 281
      lighting and heating with, 259, 264
      regulation and sale of, 261
      sad irons, 289
      stoves, burners for, 288

    Gate valve, 94

    Globe valve, 93
      angle, 94

    Grate surface, 53

    Gravity system, low pressure, 6, 15


    Heaters, combination hot-air and hot-water, 56
      direct and indirect, 28
      furnace hot-water, 122
      instantaneous, 123
      tank, 121
      wash boilers, 96

    Heating, C. A. Dunham’s system of vapor, 34, 35
      direct indirect, 30
      hot-water, 26
      indirect method of, 29, 30
      low pressure system of, 5, 6
      overhead or drop system of steam, 14
        system of hot water, 44
      plants, management of, 70
      separate return system of steam, 13
      single pipe system of steam, 6, 12, 15
      steam, 26
      surface of furnaces, 56

    Heating, radiators, 26
      two pipe system of steam, 6, 10, 11, 15

    Heat, of vaporization, 2
      specific, 37

    Hot-air furnace, 61

    Hot-water heaters, 38

    House drain, 82

    Humidifying apparatus, 215
      plants, 242

    Humidity, absolute, 196
      atmospheric, 196
      control, 244
      of the air, 196
      relative, 197, 204

    Hydraulic ram, 154
      double acting, 157
      single acting, 155

    Hydrometer, storage battery, 368

    Hygrodeik, 206

    Hygrometer, 204
      dial, 208


    Illumination, 313
      intensity of, 314
      quantity of, 314


    Kerosene, 263
      legal tests for, 263


    Lamp, base, the Edison, 311
      cord, 363
      labels, 312

    Lamps, boulevard, 287
      carbon filament, 311
      central-generator gas, 286
      daylight, electric, 324
      gas-filled electric, 324
      incandescent electric, 306
        mantle, 276
      inverted-mantle gasoline, 279

    Lamps, Mazda, 310
      miniature electric, 320, 325
      portable, gasoline, 280
      tantalum, 306
      tungsten-filament, 306
      turn-down electric, 321

    Lights, drop, 383
      flash, 326
      pilot, 383

    Lignite, 186

    Lumen, 313


    Outlet boxes, 373

    Overflow pipe, 45

    Overheated water, 47


    Peat, 187

    Pilot light, 375

    Pipes, covering, 33
      eliminator, 36
      flow, 57
      openings stopped, 113
      overflow, 40, 41
      return, 6, 10, 57
      supply, 6, 10

    Plant, hot-water heating, 37
      steam heating, 1, 5

    Plug receptacles, 378

    Plumbers friend, 113

    Plumbing, 81
      rough, 82

    Pneumatic motor valve, 237
      radiator valve, 237

    Polluted water, 134

    Pollution of wells, 134

    Pressure, absolute, 4
      gage, 4
      tank, 162
      vapor, 35, 36

    Properties of steam, 3

    Psychrometer, 207

    Pump, force, the, 146
      lift, the, 144
      tank, 146

    Pumps, 144
      chain, 151
      deep well, 150
      for driven wells, 150
      priming of, 145
      well, 148
      wooden, 148


    Radiating surface, 1, 21, 22, 27

    Radiators, air vent on, 77
      connections, 10, 47
      corner, 28
      finishings, 31
      forms of, 26
      hot-water, 28, 49
      rules for proportioning, 24, 25
      single column, 28
        pipe, 10, 15
      three column, 28
      to control, 79
      wall, 28
      water-filled, 15

    Range boilers, 115
      blow-off cock, 118
      double heater connections for, 119
      excessive pressure in, 117
      horizontal, 119
      location, 118

    Reflectors, 315
      choice of, 316
      focusing, 316
      holoplane, 315
      intensive, 316

    Registers, rules for proportioning, 55

    Regulator, combined thermostat and damper, 67
      damper, 59, 60, 67
      draft, 24
      temperature, 59, 67

    Riser, 6, 10


    Sad irons, alcohol, 292
      gasoline, 289

    Safety valve, 24, 44, 47, 67

    Septic tank, 170
      and anaerobic filter, 174
      automatic siphon for, 176
      concrete, 179
      limit of efficiency of, 178
      Universal Portland Cement Co., 179
      with sand-bed filter, 171

    Sewage, 168
      disposal, 168
      purification, 168

    Sewer, 82, 85

    Short circuiting, 334

    Sitz bath, 98

    Slicing bar, 72

    Slugging, 15

    Soil pipe, 84, 107

    Soot pocket, 80

    Stand pipe eliminator, 36

    Steam temperatures, 4

    Stop-cock, 46

    Stove, acetylene, 292
      gasoline, 288
      putty, 54

    Surface, grate, 53
      air-heating, 53

    Surging, 15

    Switch, automatic door, 378
      heater, 380
      local, 382
      service, 381

    System, high-pressure hot-water, 41
      low-pressure gravity, 6
        hot-water, 38
      overhead or drop, 14
      separate return, 13
      single pipe, 8
      two pipe, 10


    Table, air discharged from flues, 229
        required for ventilation, 220
      calorific value of American coals, 192

    Table, dew-point, 210, 211
      frost prediction, 214
      heating values of coals, 93
        gases, 252
        wood, 187, 188
      hot-air furnaces, 51
        registers, 51
      lumens per watt, 314
      prices of fuels, 191
      properties of air, 199
        steam, 3
      radiators, sizes of, 27
      record of evaporation from hot-air furnace, 217
      relative heating values of domestic fuel, 252
        humidity, 202, 203
      sizes of hard coal, 183
        heating mains, 26
        hot-air furnaces, 51
        soft coal, 184
      thermal units for one cent, 190

    Table pushes, 346

    Tank heaters, 121
      expansion, 38, 40, 41, 45, 46, 47

    Telephones, intercommunicating, 340

    Temperature regulation, 59
      hand, 59
      pneumatic, 234

    Thermostats, 62, 67
      controllers, 62, 63
      electric, 62
      motor, 64
      National Regulator Co., 235, 236
      pneumatic, 62
      time attachment, 63

    Transformers, bell-ringing, 347
      lamp, 316

    Traps, Bower, 103
      clean sweep, 103
      drum, 103, 105
      for bathroom fixture, 102, 103
      inside, 83
      non-siphoning, 105
      outside, 83
      sewer for house drains, 82
      siphoning, 106
      S, 103, 104

    Try-cocks, 22, 23

    Tungsten, 307


    Union joint, 18


    Vacuum, 5

    Valve, air, 79
      angle, 18
      check, 42, 43
      definition of, 88, 93
      disc, 19
      globe, 93
      hot-water radiator, 49
      Ohio hot-water, 49
      on cellar mains, 78
      safety, 24, 44, 47
      steam radiator, 18
      stem, 19

    Valves, definition of, 93
      globe, 93

    Vaporization, heat of, 2

    Ventilation, 219
      apparatus, 239
      by direct method of heating, 31
      by indirect method of heating, 31
      cost of, 230
      De Chaumont standard of, 219
      mechanical, 237
      of dwellings, 222, 223, 224
      Plenum method of, 239
      quantity of air required for, 220

    Vents, air, 16, 45, 48, 49
      automatic air, 16
        hot-water air, 50
      Monash No. 16 air, 16
      pipe, 83
      radiator, 16
      sewer, 85
      the Allen float, 16

    Voltage variation, effect of, 321


    Wash stands and lavatories, 101

    Waste stack, 84, 85

    Water, ammonia in, 130
      analyses, 126
      artesian, 128
      back, 115
      chlorine in, 133
      closets, 108
        siphon-jet, 108
        washdown, 109
        washout, 108
      frost, 115
      hammer, 9, 15
      hardness in, 131
      iron in, 131
      lift, 165
      medical, 128
      of condensation, 11
      organic matter in, 130
      overheated, 121
      Pokegama, 127
      polluted, 133
      river, 127
      seal, 83
      softening with hydrated silicates, 132
      supply, 87, 125
        electric power, 164
        plants, domestic, 158
          gravity, 158
      power, 163
      pressure tank system of, 160
      wind power, 164
      table, 137

    Wattmeter, periodic tests of, 354
      readings, 352
      recording, 350
      state regulation of, 353
      to read the, 350

    Well, the ideal, 140

    Wells, artesian, 140
      bored, 141
      breathing, 143
      cleaning of, 142
      concrete coverings for, 140
      construction of, 138
      curbing of, 136, 140
      cylinders for tubular, 151
      driven, 141
      dug, 139
      flowing, 138
      freezing, 144
      gases in, 142
      open, 139
      peculiarities of, 143
      safe distance in the location of, 135
      selection of the type of, 138
      surface pollution of, 135

    Wiped joints, 107

    Wire annunciator, 353

    Wiring, electric light, 372

    Wood, 187
      heating value of, 187

Transcriber's note:

Minor punctuation errors e.g. missing "." in "Fig." have been corrected.

Inconsistent hyphenation and use of ligatures has been left
e.g. cast-iron and cast iron. (Often the difference is between the
hyphenation in the text, that used in captions to illustrations
 and that used in the index.)

Both gasolene and gasoline are used in the text

Both carburator and carburetor are used in the text

Many of the table values have errors which can be shown by graphing the
results, these have been left as printed but are noted here:

  p.5. Absolute Pressure 5, Latent heat of 958.30 should be 956.30

  Air temperature 33 degF. Weight of cu. ft. air 566.4 should be 560.4
  Air temperature 43 degF. Weight of cu. ft. air 548.4 should be 542.4
  Air temperature 49 degF. Weight of cu. ft. air 542.5 should be 541.5
  Air temperature 58 degF. Weight of cu. ft. air 534.9 should be 530.9
  Air temperature 63 degF. Weight of vapor/cu. ft. air should be 6.45

  p.203. Air Temp. 106,
    2 deg. depression of wet-bulb thermometer 95 should be 93

  p.211. Dew point. 69,
   12 deg. depression of wet-bulb thermometer 84 should be 48

  Dry-bulb temp. 39,
    12 deg. depression of wet-bulb thermometer 23 should be -23
  Dry-bulb temp. 38
     9 deg. depression of wet-bulb thermometer -6  should be 6

  p.314. Column heading should read Watts per lamp 25 40 60 100 150 250

Other errors found:

  Page  |  Original       Corrected
  number|   text           text
  33    |asbestus plaster             |Asbetos is used elsewhere but
        |                             |this could be a trade name so it
        |                             |has been left as printed.
  55    |two layers of asbestus paper |       As above.
  56    |heating the house            |The "us" in house was upside-down.
  93    |pipe to which A is attached  |A should be in italics.
  100   |bath tubs, avatories         |bath tubs, lavatories
  133   |drinking porposes            |drinking purposes
  133   |elementary tract             |alimentary tract
  137   |It is flatest                |It is flattest
  161   |Boyles                       |Boyle's
  162   |wtih the pump                |with the pump
  180   |its legnth                   |its length
  181   |hould                        |should
  188   |As given by Suplees          |As given by Suplee's
  216   |hydrodeik                    |hygrodeik
  220   |Cubic feet or pure air       |Cubic feet of pure air
  239   |containg coils               |containing coils
  243   |sheet-met a surfaces         |sheet-metal surfaces
  259   |and explosion                |an explosion
  268   |The vitally improtant        |The vitally important
  269   |end of the supending bar     |end of the suspending bar
  269   |gasoline in the caburetor    |gasoline in the carburetor
  270   |gasoline for the stove _S_   | gasoline for the stove _R_
  272   |Boyles law                   |Boyle's law
  279   |Inverted-mantel Gasoline Lamp|Inverted-mantle Gasoline Lamp
  281   |percolating trough the tube  |percolating through the tube
  305   |elect ic transmission        |electric transmission
  309   |the electrotromotive force   |electromotive force
  319   |1000 746 = 1.3 horsepower    |1000/746 = 1.3 horsepower
  320   |Minature screw base          |Miniature screw base
  329   |also shown in Fig. 288       | also shown in Fig. 228
  343   |the contact peice            |the contact piece
  345   |window burgler alarm         |window burglar alarm
  347   |inserted in the floor place  |inserted in the floor plate
  352   |at the begining              |at the beginning
  356   |require severals hours       |require several hours
  357   |The amper-hour               |The ampere-hour
  358   |If the cells singly give     |If the cells singly give
        |20 volts, the battery will   |20 amperes, the battery will
        |give 20 volts                |give 20 amperes
  385   |Boyles' law, definition      |Boyle's law, definition
  387   |blau, 251                    |Blau, 251
  390   |DeChaumont                   |De Chaumont

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