| By Author | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Title | [ A B C D E F G H I J K L M N O P Q R S T U V W X Y Z | Other Symbols ] |
| By Language |
|
Download this book: [ ASCII | HTML | PDF ] Look for this book on Amazon Tweet |
Title: Scientific American Supplement, No. 441, June 14, 1884.
Author: Various
Language: English
As this book started as an ASCII text book there are no pictures available.
*** Start of this LibraryBlog Digital Book "Scientific American Supplement, No. 441, June 14, 1884." ***
[Illustration]
SCIENTIFIC AMERICAN SUPPLEMENT NO. 441
NEW YORK, JUNE 14, 1884
Scientific American Supplement. Vol. XVII., No. 441.
Scientific American established 1845
Scientific American Supplement, $5 a year.
Scientific American and Supplement, $7 a year.
* * * * *
TABLE OF CONTENTS.
I. CHEMISTRY AND METALLURGY.--On Electrolysis.--Precipitation
of lead, thallium, silver, bismuth, manganese, etc.--By H.
SCHUCHT
The Electro-Chemical Equivalent of Silver
Zircon.--How it can be rendered soluble.--By F. STOLBA
A New Process for Making Wrought Iron Directly from the Ore.
--Comparison with other processes.--With descriptions and
engravings of the apparatus used
Some Remarks on the Determination of Hardness in Water
On the changes which Take Place in the Conversion of Hay
into Ensilage.--By F.J. Lloyd
II. ENGINEERING AND MECHANICS.--Faure's Machine for
Decorticating Sugar Cane.--With full description
and 13 figures
The Generation of Steam and the Thermodynamic Problems
Involved.--By WM. ANDERSON.--Apparatus used in the
experimental determination of the heat of combustion and
the laws which govern its development.--Ingredients of
fuel.--Potential energy of fuel.--With 7 figures and
several tables
Planetary Wheel Trains.--Rotations of the wheels relatively
to the train arm.--By Prof. C.W. MACCORD
The Pantanemone.--A New Windwheel.--1 engraving
Relvas's New Life Boat.--With engraving
Experiments with Double Barreled Guns and Rifles.
--Cause of the divergence of the charge.--4 figures
Improved Ball Turning Machine.--1 figure
Cooling Apparatus for Injection Water.--With engraving
Corrugated Disk Pulleys.--1 engraving
III. TECHNOLOGY.--A New Standard Light
Dr. Feussner's New Polarizing Prism.--Points of difference
between the old and new prisms.--By P.R. SLEEMAN
Density and Pressure of Detonating Gas
IV. ELECTRICITY, LIGHT, ETC.--Early History of the Telegraph.
--Pyrsia, or the system of telegraphy among the Greeks.
--Communication by means of characters and the telescope.
--Introduction of the magnetic telegraph between Baltimore
and Washington
The Kravogl Electro Motor and its Conversion Into a Dynamo
Electric Machine.--5 figures
Bornhardt's Electric Machine for Blasting in Mines.
--15 figures
Pritchett's Electric Fire Alarm.--1 figure
A Standard Thermopile
Telephonic Transmission without Receivers.--Some of the
apparatus exhibited at the annual meeting of the French
Society of Physics.--Telephonic transmission through a
chain of persons
Diffraction Phenomena during Total Solar Eclipses.--By G.D.
Hiscox
V. BOTANY AND HORTICULTURE.--Gum Diseases in Trees.--
Cause and contagion of the same
Drinkstone Park.--Trees and plants cultivated therein.--
With 2 engravings
VI. MEDICINE AND HYGIENE.--Miryachit.--A newly-discovered
disease of the nervous system, and its analogues.--By WM. A.
HAMMOND
VII. MISCELLANEOUS.--Turkish Baths for Horses.--With
diagram.
* * * * *
FAURE'S MACHINE FOR DECORTICATING SUGAR-CANE.
The object of the apparatus shown in the accompanying engraving is to
effect a separation of the tough epidermis of the sugar-cane from the
internal spongy pith which is to be pressed. Its function consists in
isolating and separating the cells from their cortex, and in putting
them in direct contact with the rollers or cylinders of the mill.
After their passage into the apparatus, which is naturally placed in a
line with the endless chain that carries them to the mill, the canes
arrive in less compact layers, pass through much narrower spaces, and
finally undergo a more efficient pressure, which is shown by an
abundant flow of juice. The first trials of the machine were made in
1879 at the Pointe Simon Works, at Martinique, with the small type
that was shown at the Paris Exhibition of 1878. These experiments,
which were applied to a work of 3,000 kilos of cane per hour, gave
entire satisfaction, and decided the owners of three of the colonial
works (Pointe Simon, Larcinty, and Marin) to adopt it for the season
of 1880.
The apparatus is shown in longitudinal section in Fig. 1, and in plan
in Fig. 2.
Fig. 3 gives a transverse section passing through the line 3-4, and
Fig. 4 an external view on the side whence the decorticated canes make
their exit from the apparatus.
[Illustration: FAURE'S MACHINE FOR DECORTICATING SUGAR CANE.]
The other figures relate to details that will be referred to further
along.
_The Decorticating Cylinder._--The principal part of the apparatus is
a hollow drum, A, of cast iron, 430 mm. in internal diameter by 1.41
m. in length, which is keyed at its two extremities to the shaft, a.
Externally, this drum (which is represented apart in transverse
section in Fig. 5) has the form of an octagonal prism with well
dressed projections between which are fixed the eight plates, C, that
constitute the decorticating cylinder. These plates, which are of
tempered cast iron, and one of which is shown in transverse section in
Fig. 7, when once in place form a cylindrical surface provided with 48
helicoidal, dentate channels. The length of these plates is 470 mm.
There are three of them in the direction of the generatrices of the
cylinder, and this makes a total of 24. All are strengthened by ribs
(as shown in Fig. 8), and each is fixed by 4 bolts, _c_, 20mm. in
diameter. The pitch of the helices of each tooth is very elongated,
and reaches about 7.52 m. The depth of the toothing is 18 mm.
_Frame and Endless Chain._--The cylinder thus constructed rotates with
a velocity of 50 revolutions per minute over a cylindrical vessel, B',
cast in a piece with the frame, B. This vessel is lined with two
series of tempered cast iron plates, D and D', called exit and
entrance plates, which rest thereon, through the intermedium of well
dressed pedicels, and which are held in place by six 20-millimeter
bolts. Their length is 708 mm. The entrance plates, D, are provided
with 6 spiral channels, whose pitch is equal to that of the channels
of the decorticating cylinder, C, and in the same direction. The depth
of the toothing is 10 mm.
The exit plates, D', are provided with 7 spiral channels of the same
pitch and direction as those of the preceding, but the depth of which
increases from 2 to 10 mm. The axis of the decorticating cylinder does
not coincide with that of the vessel, B', so that the free interval
for the passage of the cane continues to diminish from the entrance to
the exit.
The passage of the cane to the decorticator gives rise to a small
quantity of juice, which flows through two orifices, _b'_, into a sort
of cast iron trough, G, suspended beneath the vessel. The cane, which
is brought to the apparatus by an endless belt, empties in a conduit
formed of an inclined bottom, E, of plate iron, and two cast iron
sides provided with ribs. These sides rest upon the two ends of the
vessel, B', and are cross-braced by two flat bars, _e_, to which is
bolted the bottom, E. This conduit is prolonged beyond the
decorticating cylinder by an inclined chute, F, the bottom of which is
made of plate iron 7 mm. thick and the sides of the same material 9
mm. thick. The hollow frame, B, whose general form is like that of a
saddle, carries the bearings, _b_, in which revolves the shaft, _a_.
One of these bearings is represented in detail in Figs. 9 and 10. It
will be seen that the cap is held by bolts with sunken heads, and that
the bearing on the bushes is through horizontal surfaces only. In a
piece with this frame are cast two similar brackets, B², which support
the axle, _h_, of the endless chain. To this axle, whose diameter is
100 mm., are keyed, toward the extremities, the pinions, H, to which
correspond the endless pitch chains, _i_. These latter are formed, as
may be seen in Figs. 11 and 12, of two series of links. The shorter of
these latter are only 100 mm. in length, while the longer are 210 mm.,
and are hollowed out so as to receive the butts of the boards, I. The
chain thus formed passes over two pitch pinions, J, like the pinions,
H, that are mounted at the extremities of an axle, _j_, that revolves
in bearings, I', whose position with regard to the apparatus is
capable of being varied so as to slacken or tauten the chain, I. This
arrangement is shown in elevation in Fig. 13.
_Transmission._--The driving shaft, _k_, revolves in a pillow block,
K, cast in a piece with the frame, B. It is usually actuated by a
special motor, and carries a fly-wheel (not shown in the figure for
want of space). It receives in addition a cog-wheel, L, which
transmits its motion to the decorticating cylinder through, the
intermedium of a large wooden-toothed gear wheel, L'. The shaft, _a_,
whose diameter is 228 mm., actuates in its turn, through the pinions,
M' and M, the pitch pinion, N, upon whose prolonged hub is keyed the
pinion, M. This latter is mounted loosely upon the intermediate axle,
_m_. Motion is transmitted to the driving shaft, _h_, of the endless
chain, I, by an ordinary pitch chain, through a gearing which is shown
in Fig. 12. The pitch pinion, N', is cast in a piece with a hollow
friction cone, N², which is mounted loosely upon the shaft, _h_, and
to which corresponds a second friction cone, O. This latter is
connected by a key to a socket, _o_, upon which it slides, and which
is itself keyed to the shaft, _h_. The hub of the cone, O, is
connected by a ring with a bronze nut, _p_, mounted at the threaded
end of the shaft, _h_, and carrying a hand-wheel, P. It is only
necessary to turn this latter in one direction or the other in order
to throw the two cones into or out of gear.
If we allow that the motor has a velocity of 70 revolutions per
minute, the decorticating cylinder will run at the rate of 50, and the
sugar-cane will move forward at the rate of 12 meters per minute.
This new machine is a very simple and powerful one. The decortication
is effected with wonderful rapidity, and the canes, opened throughout
their entire length and at all points of their circumference, leave
the apparatus in a state that allows of no doubt as to what the result
of the pressure will be that they have to undergo. There is no
tearing, no trituration, no loss of juice, but merely a simple
preparation for a rational pressure effected under most favorable
conditions.
The apparatus, which is made in several sizes, has already received
numerous applications in Martinique, Trinidad, Cuba, Antigua, St.
Domingo, Peru, Australia, the Mauritius Islands, and
Brazil.--_Publication Industrielle._
* * * * *
MOVING A BRIDGE.
An interesting piece of engineering work has recently been
accomplished at Bristol, England, which consisted in the moving of a
foot-bridge 134 feet in length, bodily, down the river a considerable
distance. The pontoons by means of which the bridge was floated to its
new position consisted of four 80-ton barges, braced together so as to
form one solid structure 64 feet in width, and were placed in position
soon after the tide commenced to rise. At six o'clock A.M. the top of
the stages, which was 24 feet above the water, touched the under part
of the bridge, and in a quarter of an hour later both ends rose from
their foundations. When the tide had risen 4 ft. the stage and bridge
were floated to the new position, when at 8.30 the girders dropped on
to their beds.
* * * * *
THE GENERATION OF STEAM, AND THE THERMODYNAMIC PROBLEMS
INVOLVED.[1]
[Footnote 1: Lecture delivered at the Institution of Civil
Engineers, session 1883-84. For the illustrations we are indebted
to the courtesy of Mr. J. Forrest, the secretary.]
By Mr. WILLIAM ANDERSON, M.I.C.E.
It will not be necessary to commence this lecture by explaining the
origin of fuel; it will be sufficient if I remind you that it is to
the action of the complex rays of the sun upon the foliage of plants
that we mainly owe our supply of combustibles. The tree trunks and
branches of our forests, as well as the subterranean deposits of coal
and naphtha, at one time formed portions of the atmosphere in the form
of carbonic acid gas; that gas was decomposed by the energy of the
solar rays, the carbon and the oxygen were placed in positions of
advantage with respect to each other--endowed with potential energy;
and it is my duty this evening to show how we can best make use of
these relations, and by once more combining the constituents of fuel
with the oxygen of the air, reverse the action which caused the growth
of the plants, that is to say, by destroying the plant reproduce the
heat and light which fostered it. The energy which can be set free by
this process cannot be greater than that derived originally from the
sun, and which, acting through the frail mechanism of green leaves,
tore asunder the strong bonds of chemical affinity wherein the carbon
and oxygen were hound, converting the former into the ligneous
portions of the plants and setting the latter free for other uses. The
power thus silently exerted is enormous; for every ton of carbon
separated in twelve hours necessitates an expenditure of energy
represented by at least 1,058 horse power, but the action is spread
over an enormous area of leaf surface, rendered necessary by the small
proportion of carbonic acid contained in the air, by measure only
1/2000 part, and hence the action is silent and imperceptible. It is
now conceded on all hands that what is termed heat is the energy of
molecular motion, and that this motion is convertible into various
kinds and obeys the general laws relating to motion. Two substances
brought within the range of chemical affinity unite with more or less
violence; the motion of transition of the particles is transformed,
wholly or in part, into a vibratory or rotary motion, either of the
particles themselves or the interatomic ether; and according to the
quality of the motions we are as a rule, besides other effects, made
conscious of heat or light, or of both. When these emanations come to
be examined they are found to be complex in the extreme, intimately
bound up together, and yet capable of being separated and analyzed.
As soon as the law of definite chemical combination was firmly
established, the circumstance that changes of temperature accompanied
most chemical combinations was noticed, and chemists were not long in
suspecting that the amount of heat developed or absorbed by chemical
reaction should be as much a property of the substances entering into
combination as their atomic weights. Solid ground for this expectation
lies in the dynamic theory of heat. A body of water at a given height
is competent by its fall to produce a definite and invariable quantity
of heat or work, and in the same way two substances falling together
in chemical union acquire a definite amount of kinetic energy, which,
if not expended in the work of molecular changes, may also by suitable
arrangements be made to manifest a definite and invariable quantity of
heat.
At the end of last century Lavoisier and Laplace, and after them, down
to our own time, Dulong, Desprez, Favre and Silbermann, Andrews,
Berthelot, Thomson, and others, devoted much time and labor to the
experimental determination of the heat of combustion and the laws
which governed its development. Messrs. Favre and Silbermann, in
particular, between the years 1845 and 1852, carried out a splendid
series of experiments by means of the apparatus partly represented in
Fig. 1 (opposite), which is a drawing one-third the natural size of
the calorimeter employed. It consisted essentially of a combustion
chamber formed of thin copper, gilt internally. The upper part of the
chamber was fitted with a cover through which the combustible could be
introduced, with a pipe for a gas jet, with a peep hole closed by
adiathermanous but transparent substances, alum and glass, and with a
branch leading to a thin copper coil surrounding the lower part of the
chamber and descending below it. The whole of this portion of the
apparatus was plunged into a thin copper vessel, silvered internally
and filled with water, which was kept thoroughly mixed by means of
agitators. This second vessel stood inside a third one, the sides and
bottom of which were covered with the skins of swans with the down on,
and the whole was immersed in a fourth vessel tilled with water, kept
at the average temperature of the laboratory. Suitable thermometers of
great delicacy were provided, and all manner of precautions were taken
to prevent loss of heat.
[Illustration: THE GENERATION OF STEAM. Fig 1.]
It is impossible not to admire the ingenuity and skill exhibited in
the details of the apparatus, in the various accessories for
generating and storing the gases used, and for absorbing and weighing
the products of combustion; but it is a matter of regret that the
experiments should have been carried out on so small a scale. For
example, the little cage which held the solid fuel tested was only 5/8
inch diameter by barely 2 inches high, and held only 38 grains of
charcoal, the combustion occupying about sixteen minutes. Favre and
Silbermann adopted the plan of ascertaining the weight of the
substances consumed by calculation from the weight of the products of
combustion. Carbonic acid was absorbed by caustic potash, as also was
carbonic oxide, after having been oxidized to carbonic acid by heated
oxide of copper, and the vapor of water was absorbed by concentrated
sulphuric acid. The adoption of this system showed that it was in any
case necessary to analyze the products of combustion in order to
detect imperfect action. Thus, in the case of substances containing
carbon, carbonic oxide was always present to a variable extent with
the carbonic acid, and corrections were necessary in order to
determine the total heat due to the complete combination of the
substance with oxygen. Another advantage gained was that the
absorption of the products of combustion prevents any sensible
alteration in the volumes during the process, so that corrections for
the heat absorbed in the work of displacing the atmosphere were not
required. The experiments on various substances were repeated many
times. The mean results for those in which we are immediately
interested are given in Table I., next column.
Comparison with later determinations have established their
substantial accuracy. The general conclusion arrived at is thus
stated:
"As a rule there is an equality between the heat disengaged or
absorbed in the acts, respectively, of chemical combination or
decomposition of the same elements, so that the heat evolved during
the combination of two simple or com-pound substances is equal to the
heat absorbed at the time of their chemical segregation."
TABLE I.--SUBSTANCES ENTERING INTO THE COMPOSITION OF FUEL.
-----------------------+-------------+-----------+-------------------+
| | Heat evolved in |
| Symbol and Atomic |the Combustion of |
| Weight. | 1 lb. of Fuel. |
+------------+------------+--------+----------+
| | | |In Pounds |
| | | In | of Water |
| | |British |Evaporated|
| Before | After |Thermal | from and |
| Combustion | Combustion | Units. | at 212°. |
+------------+------------+--------+----------+
Hydrogen burned | H 1 | H2O 18 | 62,032 | 64.21 |
in oxygen. | | | | |
-----------------------+------------+------------+--------+----------+
Carbon burned to | C 12 | CO 28 | 4,451 | 4.61 |
carbonic oxide. | | | | |
-----------------------+------------+------------+--------+----------+
Carbon burned to | C 12 | CO2 44 | 14,544 | 15.06 |
carbonic acid. | | | | |
-----------------------+------------+------------+--------+----------+
Carbonic oxide burned | CO 28 | CO2 44 | 4,326 | 4.48 |
to carbonic acid. | | | | |
-----------------------+------------+------------+--------+----------+
Olefiant gas (ethylene)| C2H4 28 | 2CO2 124 | 21,343 | 22.09 |
burnt in oxygen. | | 2H2O | | |
-----------------------+------------+------------+--------+----------+
Marsh gas (methane) | CH4 16 | 2CO2 80 | 23,513 | 24.34 |
burnt in oxygen. | | 2H2O | | |
-----------------------+------------+------------+--------+----------+
Composition of air--
by volume 0.788 N + 0.197 O + 0.001 CO2 + 0.014 H2O
----------------------------------------------------
by weight 0.771 N + 0.218 O + 0.009 CO2 + 0.017 H2O
This law is, however, subject to some apparent exceptions. Carbon
burned in protoxide of nitrogen, or laughing gas, N_{2}O, produces
about 38 per cent. more heat than the same substance burned in pure
oxygen, notwithstanding that the work of decomposing the protoxide of
nitrogen has to be performed. In marsh gas, or methane, CH_{4}, again,
the energy of combustion is considerably less than that due to the
burning of its carbon and hydrogen separately. These exceptions
probably arise from the circumstance that the energy of chemical
action is absorbed to a greater or less degree in effecting molecular
changes, as, for example, the combustion of 1 pound of nitrogen to
form protoxide of nitrogen results in the absorption of 1,157 units of
heat. Berthelot states, as one of the fundamental principles of
thermochemistry, "that the quantity of heat evolved is the measure of
the sum of the chemical and physical work accomplished in the
reaction"; and such a law will no doubt account for the phenomena
above noted. The equivalent heat of combustion of the compounds we
have practically to deal with has been experimentally determined, and
therefore constitutes a secure basis on which to establish
calculations of the caloric value of fuel; and in doing so, with
respect to substances composed of carbon, hydrogen, and oxygen, it is
convenient to reduce the hydrogen to its heat-producing equivalent of
carbon. The heat of combustion of hydrogen being 62,032 units, that of
carbon 14,544 units, it follows that 4.265 times the weight of
hydrogen will represent an equivalent amount of carbon. With respect
to the oxygen, it is found that it exists in combination with the
hydrogen in the form of water, and, being combined already, abstracts
its combining equivalent of hydrogen from the efficient ingredients of
the fuel; and hence hydrogen, to the extent of 1/8 of the weight of
the oxygen, must be deducted. The general formula then becomes:
Heat of combustion = 14,544 {C + 4.265 (H-(O/8))},
and water evaporated from and at 212°, taking 966 units as the heat
necessary to evaporate 1 pound of water,
lb. evaporated = 15.06 {C + 4.265 (H-(O/8))},
carbon, hydrogen, and oxygen being taken at their weight per cent. in
the fuel. Strictly speaking, marsh gas should be separately
determined. It often happens that available energy is not in a form in
which it can be applied directly to our needs. The water flowing down
from the mountains in the neighborhood of the Alpine tunnels was
competent to provide the power necessary for boring through them, but
it was not in a form in which it could be directly applied. The
kinetic energy of the water had first to be changed into the potential
energy of air under pressure, then, in that form, by suitable
mechanism, it was used with signal success to disintegrate and
excavate the hard rock of the tunnels. The energy resulting from
combustion is also incapable of being directly transformed into useful
motive power; it must first be converted into potential force of steam
or air at high temperature and pressure, and then applied by means of
suitable heat engines to produce the motions we require. It is
probably to this circumstance that we must attribute the slowness of
the human race to take advantage of the energy of combustion. The
history of the steam engine hardly dates back 200 years, a very small
fraction of the centuries during which man has existed, even since
historic times.
The apparatus by means of which the potential energy of fuel with
respect to oxygen is converted into the potential energy of steam, we
call a steam boiler; and although it has neither cylinder nor piston,
crank nor fly wheel, I claim for it that it is a veritable heat
engine, because it transmits the undulations and vibrations caused by
the energy of chemical combination in the fuel to the water in the
boiler; these motions expend themselves in overcoming the liquid
cohesion of the water and imparting to its molecules that vigor of
motion which converts them into the molecules of a gas which,
impinging on the surfaces which confine it and form the steam space,
declare their presence and energy in the shape of pressure and
temperature. A steam pumping engine, which furnishes water under high
pressure to raise loads by means of hydraulic cranes, is not more
truly a heat engine than a simple boiler, for the latter converts the
latent energy of fuel into the latent energy of steam, just as the
pumping engine converts the latent energy of steam into the latent
energy of the pumped-up accumulator or the hoisted weight.
If I am justified in taking this view, then I am justified in applying
to my heat engine the general principles laid down in 1824 by Sadi
Carnot, namely, that the proportion of work which can be obtained out
of any substance working between two temperatures depends entirely and
solely upon the difference between the temperatures at the beginning
and end of the operation; that is to say, if T be the higher
temperature at the beginning, and _t_ the lower temperature at the end
of the action, then the maximum possible work to be got out of the
substance will be a function of (T-_t_). The greatest range of
temperature possible or conceivable is from the absolute temperature
of the substance at the commencement of the operation down to absolute
zero of temperature, and the fraction of this which can be utilized is
the ratio which the range of temperature through which the substance
is working bears to the absolute temperature at the commencement of
the action. If W = the greatest amount of effect to be expected, T and
_t_ the absolute temperatures, and H the total quantity of heat
(expressed in foot pounds or in water evaporated, as the case may be)
potential in the substance at the higher temperature, T, at the
beginning of the operation, then Carnot's law is expressed by the
equation:
/ T - t \
W = H( ------- )
\ T /
I will illustrate this important doctrine in the manner which Carnot
himself suggested.
[Illustration: THE GENERATION OF STEAM. Fig 2.]
Fig. 2 represents a hillside rising from the sea. Some distance up
there is a lake, L, fed by streams coming down from a still higher
level. Lower down on the slope is a millpond, P, the tail race from
which falls into the sea. At the millpond is established a factory,
the turbine driving which is supplied with water by a pipe descending
from the lake, L. Datum is the mean sea level; the level of the lake
is T, and of the millpond _t_. Q is the weight of water falling
through the turbine per minute. The mean sea level is the lowest level
to which the water can possibly fall; hence its greatest potential
energy, that of its position in the lake, = QT = H. The water is
working between the absolute levels, T and _t_; hence, according to
Carnot, the maximum effect, W, to be expected is--
/ T - t \
W = H( ------- )
\ T /
/ T - t \
but H = QT [therefore] W = Q T( ------- )
\ T /
W = Q (T - t),
that is to say, the greatest amount of work which can be expected is
found by multiplying the weight of water into the clear fall, which
is, of course, self-evident.
Now, how can the quantity of work to be got out of a given weight of
water be increased without in any way improving the efficiency of the
turbine? In two ways:
1. By collecting the water higher up the mountain, and by that means
increasing T.
2. By placing the turbine lower down, nearer the sea, and by that
means reducing _t_.
Now, the sea level corresponds to the absolute zero of temperature,
and the heights T and _t_ to the maximum and minimum temperatures
between which the substance is working; therefore similarly, the way
to increase the efficiency of a heat engine, such as a boiler, is to
raise the temperature of the furnace to the utmost, and reduce the
heat of the smoke to the lowest possible point. It should be noted, in
addition, that it is immaterial what liquid there may be in the lake;
whether water, oil, mercury, or what not, the law will equally apply,
and so in a heat engine, the nature of the working substance, provided
that it does not change its physical state during a cycle, does not
affect the question of efficiency with which the heat being expended
is so utilized. To make this matter clearer, and give it a practical
bearing, I will give the symbols a numerical value, and for this
purpose I will, for the sake of simplicity, suppose that the fuel used
is pure carbon, such as coke or charcoal, the heat of combustion of
which is 14,544 units, that the specific heat of air, and of the
products of combustion at constant pressure, is 0.238, that only
sufficient air is passed through the fire to supply the quantity of
oxygen theoretically required for the combustion of the carbon, and
that the temperature of the air is at 60° Fahrenheit = 520° absolute.
The symbol T represents the absolute temperature of the furnace, a
value which is easily calculated in the following manner: 1 lb. of
carbon requires 2-2/3 lb. of oxygen to convert it into carbonic acid,
and this quantity is furnished by 12.2 lb. of air, the result being
13.2 lb. of gases, heated by 14,544 units of heat due to the energy of
combustion; therefore:
14,544 units
T = 520° + ------------------ = 5,150° absolute.
13.2 lb. X 0.238
The lower temperature, _t_, we may take as that of the feed water, say
at 100° or 560° absolute, for by means of artificial draught and
sufficiently extending the heating surface, the temperature of the
smoke may be reduced to very nearly that of the feed water. Under such
circumstances the proportion of heat which can be realized is
5,150° - 560°
= --------------- = 0.891;
5,150°
that is to say, under the extremely favorable if not impracticable
conditions assumed, there must be a loss of 11 per cent. Next, to give
a numerical value to the potential energy, H, to be derived from a
pound of carbon, calculating from absolute zero, the specific heat of
carbon being 0.25, and absolute temperature of air 520°:
Units.
1 lb. of carbon X 0.25 X 520 = 130
12.2 of air X 0.238 X 520 = 1,485
Heat of combustion = 14,544
------
16,159
Deduct heat equivalent to work of \
displacing atmosphere by products of }
combustion raised from 60° to 100°, } 32
or from 149.8 cubic feet to 161.3 }
cubic feet, /
------
Total units of heat available 16,127
Equal to 16.69 lb. of water evaporated from and at 212°. Hence the
greatest possible evaporation from and at 212° from a lb. of carbon--
16,159 u. X 0.891 - 32 u.
W = --------------------------- = 14.87 lb.
966 u.
I will now take a definite case, and compare the potential energy of a
certain kind of fuel with the results actually obtained. For this
purpose the boiler of the eight-horse portable engine, which gained
the first prize at the Cardiff show of the Royal Agricultural Society
in 1872, will serve very well, because the trials, all the details of
which are set forth very fully in vol. ix. of the _Journal_ of the
Society, were carried out with great care and skill by Sir Frederick
Bramwell and the late Mr. Menelaus; indeed, the only fact left
undetermined was the temperature of the furnace, an omission due to
the want of a trustworthy pyrometer, a want which has not been
satisfied to this day.[2]
[Footnote 2: In the fifty-second volume of the _Proceedings_
(1887-78), page 154, will be found a remarkable experiment on the
evaporative power of a vertical boiler with internal circulating
pipes. The experiment was conducted by Sir Frederick Bramwell and
Dr. Russell, and is remarkable in this respect, that the quantity
of air admitted to the fuel, the loss by convection and
radiation, and the composition of the smoke were determined. The
facts observed were as follows:
Steam pressure 53 lb................................... = 300.6° F.
lb.
Fuel--Water in coke and wood........................... 26.08
Ash.............................................. 10.53
Hydrogen, oxygen, nitrogen, and sulphur.......... 7.18
------
Total non-combustible..................... 43.79
Carbon, being useful combustible................. 194.46
------
Total fuel................................ 238.25
Air per pound of carbon................................ 17-1/8 lb.
Time of experiment..................................... 4 h. 12 min.
Water evaporated from 60° into steam at 53 lb. pressure 1,620 lb.
Heat lost by radiation and convection.................. 70,430 units.
Mean temperature of chimney............................ 700° F.
" " " air................................ 70° F.
No combustible gas was found in the chimney.
I will apply Carnot's doctrine to this case.
Potential energy of the fuel with respect to absolute zero:
Units.
239.25 lb. × 530° abs. × 0.238 ...................... = 30,053
194.46 lb. × 17-1/8 × 530° × 0.238,
the weight and heat of air....................... 420,660
194.46 × 14,544 units heat of combustion of carbon... 2,828,200
---------
Total energy 3,278,813
Heat absorbed in evaporating 26.08 lb. of water
in fuel............................................ -29,888
---------
Available energy.......................... 3,248,425
Temperature of furnace--
The whole of the fuel was heated up, but the heat absorbed in the
evaporation of the water lowered the temperature of the furnace,
and must be deducted from the heat of combustion.
Units.
Heat of combustion................................... 2,828,200
" " evaporation of 26.08 lb. water............... -29,888
---------
Available heat of combustion.............. 2,798,312
Dividing by 238.25 lb. gives the heat per 1 lb.
of fuel used................................... = 11,745 units.
And temperature of furnace:
11,745 units/(18.125 lb. × 0.238) + 530°......... = 3,253°
Temperature of chimney 700° + 460°............... = 1,160°
Maximum duty (3,253° - 1,160°)/3,253°............ = 0.643°
Work of displacing atmosphere by smoke at 700°:
Cubic feet.
Volumes of gases at 70°........................ = 228.3
" " " " 700°........................ = 499.8
-----
Increase of volume.................... 271.5
Units.
Work done=
(194.46 lb. × 271.5 cub. ft. × 144 sq. in. × 15 lb.)
/722 units ..................................... = 147,720
Maximum amount of work to be expected =
3,248,425 × 0.643.............................. = 2,101,700
Deduct work of displacing atmosphere............. = 147,720
---------
Available work........................ 1,953,980
Actual work done:
Units.
1,620 lb. of water raised from 60° and turned
into steam at 53 lb..... ...................... = 1,855,900
Loss by radiation and convection................. 70,430
10-1/2 lb. ashes left, say at 500°............... 1,129
---------
Total work actually done.............. 1,927,459
Unaccounted for.................................. 26,521
---------
Calculated available work........................ 1,953,980
The unaccounted-for work, therefore, amounts to only 1½ per cent.
of the calculated available work.
Sir Frederick Bramwell ingeniously arranged his data in the form
of a balance sheet, and showed 253,979 units unaccounted for; but
if from this we deduct the work lost in displacing the air, the
unaccounted-for heat falls to less than 4 per cent. of the total
heat of combustion. These results show how extremely accurate the
observations must have been, and that the loss mainly arises from
convection and radiation from the boiler.]
The data necessary for our purpose are:
Steam pressure 80 lb. temperature 324° = 784° absolute.
Mean temperature of smoke 389° = 849° "
Water evaporated per 1 lb of coal, from and at 212° 11.83 lb.
Temperature of the air 60° = 520° absolute.
" of feed water 209° = 669° "
Heating surface 220 square feet.
Grate surface 3.29 feet.
Coal burnt per hour 41 lb.
The fuel used was a smokeless Welsh coal, from the Llangennech
colleries. It was analyzed by Mr. Snelus, of the Dowlais Ironworks,
and in Table II. are exhibited the details of its composition, and the
weight and volume of air required for its combustion. The total heat
of combustion in 1 lb of water evaporated:
= 15.06 × (0.8497 + 4.265 × (0.426 - 0.035/8))
= 15.24 lb. of water from and at 212°
= 14,727 units of heat.
TABLE II.--PROPERTIES OF LLANGENNECH COAL.
---------------------+----------+------------+---------------------+
| | | |
| | | Products of |
| | Oxygen | Combustion at 32° F.|
| Analyses | required +--------+------------+
| of 1 lb. | for | | |
| of Coal. | Combustion.| Cubic | Volume |
| | Pounds. | feet. | per cent. |
---------------------+----------+------------+--------+------------+
Carbon........... | 0.8497 | 2.266 | 25.3 | 11.1 |
Hydrogen......... | 0.0426 | 0.309 | 7.6 | 3.4 |
Oxygen........... | 0.0350 | --- | --- | --- |
Sulphur.......... | 0.0042 | --- | --- | _ --- |
Nitrogen......... | 0.1045 | --- | 0.18 | | |
Ash.............. | 0.0540 | --- | --- | | |
+----------+------------+ | | 85.5 |
| | | | | |
Total........... | 1.0000 | 2.572 | --- | | |
9-1/3.lb nitrogen | --- | --- | 118.9 | | |
6 lb. excess of air. | --- | --- | 71.4 | _| |
+----------+------------+--------+------------+
Total cubic feet of | | | | |
products per 1 lb. | | | | |
of coal........... | -- | -- | 226.4 | 100.0 |
---------------------+----------+------------+--------+------------+
The temperature of the furnace not having been determined, we must
calculate it on the supposition, which will be justified later on,
that 50 per cent more air was admitted than was theoretically
necessary to supply the oxygen required for perfect combustion. This
would make 18 lb. of air per 1 lb. of coal; consequently 19 lb. of
gases would be heated by 14,727 units of heat. Hence:
14,727 u.
T = ---------------- = 3,257°
19 lb. × 0.238
above the temperatures of the air, or 3,777° absolute. The temperature
of the smoke, _t_, was 849° absolute; hence the maximum duty would be
3,777° - 849°
--------------- = 0.7752.
3,777°
The specific heat of coal is very nearly that of gases at constant
pressure, and may, without sensible error, be taken as such. The
potential energy of 1 lb. of coal, therefore, with reference to the
oxygen with which it will combine, and calculated from absolute zero,
is:
Units.
19 lb. of coal and air at the temperature
of the air contained 19 lb. × 520° × 0.238 2,350
Heat of combustion 14,727
-------
17,078
Deduct heat expended in displacing atmosphere 151 cubic feet - 422
------
Total potential energy 16,656
Hence work to be expected from the boiler:
/ 3,777° - 849° \
= 17,078 units X ( --------------- ) - 422 units
\ 3,777° /
---------------------------------------------- = 13.27 lb.
966 units
of water evaporated from and at 212°, corresponding to 12,819 units.
The actual result obtained was 11.83 lb.; hence the efficiency of this
boiler was
11.83
------- = 0.892.
13.27
I have already claimed for a boiler that it is a veritable heat
engine, and I have ventured to construct an indicator diagram to
illustrate its working. The rate of transfer of heat from the furnace
to the water in the boiler, at any given point, is some way
proportional to the difference of temperature, and the quantity of
heat in the gases is proportional to their temperatures. Draw a base
line representing -460° Fahr., the absolute zero of temperature. At
one end erect an ordinate, upon which set off T = 3,777°, the
temperature of the furnace. At 849° = _t_, on the scale of
temperature, draw a line parallel to the base, and mark on it a length
proportional to the heating surface of the boiler; join T by a
diagonal with the extremity of this line, and drop a perpendicular on
to the zero line. The temperature of the water in the boiler being
uniform, the ordinates bounded by the sloping line, and by the line,
_t_, will at any point be approximately proportional to the rate of
transmission of heat, and the shaded area above _t_ will be
proportional to the quantity of heat imparted to the water. Join T by
another diagonal with extremity of the heating surface on the zero
line, then the larger triangle, standing on the zero line, will
represent the whole of the heat of combustion, and the ratio of the
two triangles will be as the lengths of their respective bases, that
is, as (T - _t_) / T, which is the expression we have already used. The
heating surface was 220 square feet, and it was competent to transmit
the energy developed by 41 lb. of coal consumed per hour = 12,819 u. ×
41 u. = 525,572 units, equal to an average of 2,389 units per square
foot per hour; this value will correspond to the mean pressure in an
ordinary diagram, for it is a measure of the energy with which
molecular motion is transferred from the heated gases to the
boiler-plate, and so to the water. The mean rate of transmission,
multiplied by the area of heating surface, gives the area of the
shaded portion of the figure, which is the total work which should
have been done, that is to say, the work of evaporating 544 lb. of
water per hour. The actual work done, however, was only 485 lb. To
give the speculations we have indulged in a practical turn, it will be
necessary to examine in detail the terms of Carnot's formula. Carnot
labored under great disadvantages. He adhered to the emission theory
of heat; he was unacquainted with its dynamic equivalent; he did not
know the reason of the difference between the specific heat of air at
constant pressure and at constant volume, the idea of an absolute zero
of temperature had not been broached; but the genius of the man, while
it made him lament the want of knowledge which he felt must be
attainable, also enabled him to penetrate the gloom by which he was
surrounded, and enunciate propositions respecting the theory of heat
engines, which the knowledge we now possess enables us to admit as
true. His propositions are:
1. The motive power of heat is independent of the agents employed to
develop it, and its quantity is determined solely by the temperature
of the bodies between which the final transfer of caloric takes place.
2. The temperature of the agent must in the first instance be raised
to the highest degree possible in order to obtain a great fall of
caloric, and as a consequence a large production of motive power.
3. For the same reason the cooling of the agent must be carried to as
low a degree as possible.
4. Matters must be so arranged that the passage of the elastic agent
from the higher to the lower temperature must be due to an increase of
volume, that is to say, the cooling of the agent must be caused by its
rarefaction.
This last proposition indicates the defective information which Carnot
possessed. He knew that expansion of the elastic agent was accompanied
by a fall of temperature, but he did not know that that fall was due
to the conversion of heat into work. We should state this clause more
correctly by saying that "the cooling of the agent must be caused by
the external work it performs." In accordance with these propositions,
it is immaterial what the heated gases or vapors in the furnace of a
boiler may be, provided that they cool by doing external work and, in
passing over the boiler surfaces, impart their heat energy to the
water. The temperature of the furnace, it follows, must be kept as
high as possible. The process of combustion is usually complex. First,
in the case of coal, close to the fire-bars complete combustion of the
red hot carbon takes place, and the heat so developed distills the
volatile hydrocarbons and moisture in the upper layers of the fuel.
The inflammable gases ignite on or near the surface of the fuel, if
there be a sufficient supply of air, and burn with a bright flame for
a considerable distance around the boiler. If the layer of fuel be
thin, the carbonic acid formed in the first instance passes through
the fuel and mixes with the other gases. If, however, the layer of
fuel be thick, and the supply of air through the bars insufficient,
the carbonic acid is decomposed by the red hot coke, and twice the
volume of carbonic oxide is produced, and this, making its way through
the fuel, burns with a pale blue flame on the surface, the result, as
far as evolution of heat is concerned, being the same as if the
intermediate decomposition of carbonic acid had not taken place. This
property of coal has been taken advantage of by the late Sir W.
Siemens in his gas producer, where the supply of air is purposely
limited, in order that neither the hydrocarbons separated by
distillation, nor the carbonic oxide formed in the thick layer of
fuel, may be consumed in the producer, but remain in the form of crude
gas, to be utilized in his regenerative furnaces.
[Illustration: THE GENERATION OF STEAM. Fig 3.]
[Illustration: THE GENERATION OF STEAM. Fig 4.]
[Illustration: THE GENERATION OF STEAM. Fig 5.]
[Illustration: THE GENERATION OF STEAM. Fig 6.]
[Illustration: THE GENERATION OF STEAM. Fig 7.]
_(To be continued.)_
* * * * *
[Continued from SUPPLEMENT No. 437, page 6970.]
PLANETARY WHEEL-TRAINS.
By Prof. C.W. MACCORD, Sc.D.
II.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 14]
It has already been shown that the rotations of all the wheels of a
planetary train, relatively to the train-arm, are the same when the
arm is in motion as they would be if it were fixed. Now, in Fig. 14,
let A be the first and F the last wheel of an _incomplete_ train, that
is, one having but one sun-wheel. As before, let these be so connected
by intermediate gearing that, when T is stationary, a rotation of A
through _m_ degrees shall drive F through _n_ degrees: and also as
before, let T in the same time move through _a_ degrees. Then, if _m'_
represent the total motion of A, we have again,
m' = m + a, or m = m' - a.
This is, clearly, the motion of A relatively to the fixed frame of the
machine; and is measured from a fixed vertical line through the
center of A. Now, if we wish to express the total motion of F
relatively to the same fixed frame, we must measure it from a vertical
line through the center of F, wherever that maybe; which gives in this
case:
n' = n + a, or n = n' - a.
but with respect to the train-arm when at rest, we have:
ang. vel. A n
------------ = ---, whence again
ang. vel. F m
n' - a n
------ = --- .
m' - a m
This is the manner in which the equation is deduced by Prof. Willis,
who expressly states that it applies whether the last wheel F is or is
not concentric with the first wheel A, and also that the train may be
composed of any combinations which transmit rotation with both a
constant velocity ratio and a constant directional relation. He
designates the quantities _m'_, _n'_, _absolute revolutions_, as
distinguished from the _relative revolutions_ (that is, revolutions
relatively to the train-arm), indicated by the quantities _m_, _n_:
adding, "Hence it appears that the absolute revolutions of the wheels
of epicyclic trains are equal to the sum of their relative revolutions
to the arm, and of the arm itself, when they take place in the same
direction, and equal to the difference of these revolutions when in
the opposite direction."
In this deduction of the formula, as in that of Prof. Rankine, all the
motions are supposed to have the same direction, corresponding to that
of the hands of the clock; and in its application to any given train,
the signs of the terms must be changed in case of any contrary motion,
as explained in the preceding article.
And both the deduction and the application, in reference to these
incomplete trains in which the last wheel is carried by the
train-arm, clearly involve and depend upon the resolving of a motion
of revolution into the components of a circular translation and a
rotation, in the manner previously discussed.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 15]
To illustrate: Take the simple case of two equal wheels, Fig. 15, of
which the central one A is fixed. Supposing first A for the moment
released and the arm to be fixed, we see that the two wheels will turn
in opposite directions with equal velocities, which gives _n_/_m_ = -1;
but when A is fixed and T revolves, we have _m'_ = 0, whence in the
general formula
n' - a
------ = -1, or n' = 2 a;
-a
which means, being interpreted, that F makes two rotations about its
axis during one revolution of T, and in the same direction. Again, let
A and F be equal in the 3-wheel train, Fig. 16, the former being fixed
as before. In this case we have:
n
--- = 1, m' = 0, which gives
m
n' - a
------- = 1, [therefore] n' = 0;
-a
that is to say, the wheel F, which now evidently has a motion of
circular translation, does not rotate at all about its axis during the
revolution of the train-arm.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 16]
All this is perfectly consistent, clearly, with the hypothesis that
the motion of circular translation is a simple one, and the motion of
revolution about a fixed axis is a compound one.
Whether the hypothesis was made to substantiate the formula, or the
formula constructed to suit the hypothesis, is not a matter of
consequence. In either case, no difficulty will arise so long as the
equation is applied only to cases in which, as in those here
mentioned, that motion of revolution _can_ be resolved into those
components.
When the definition of an epicyclic train is restricted as it is by
Prof. Rankine, the consideration of the hypothesis in question is
entirely eliminated, and whether it be accepted or rejected, the whole
matter is reduced to merely adding the motion of the train-arm to the
rotation of each sun-wheel.
But in attempting to apply this formula in analyzing the action of an
incomplete train, we are required to add this motion of the train-arm,
not only to that of a sun-wheel, but to that of a planet-wheel. This
is evidently possible in the examples shown in Figs. 15 and 16,
because the motions to be added are in all respects similar: the
trains are composed of spur-wheels, and the motions, whether of
revolution, translation, or rotation, _take place in parallel planes
perpendicular to parallel axes_. This condition, which we have
emphasized, be it observed, must hold true with regard to the motions
of the first and last wheels and the train-arm, in order to make this
addition possible. It is not essential that spur-wheels should be used
exclusively or even at all; for instance, in Fig. 16, A and F may be
made bevel or screw-wheels, without affecting the action or the
analysis; but the train-arm in all cases revolves around the central
axis of the system, that is, about the axis of A, and to this the axis
of F _must_ be parallel, in order to render the deduction of the
formula, as made by Prof. Willis, and also by Prof. Goodeve, correct,
or even possible.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 17]
This will be seen by an examination of Fig. 17; in which A and B are
two equal spur-wheels, E and F two equal bevel wheels, B and E being
secured to the same shaft, and A being fixed to the frame H. As the
arm T goes round, B will also turn in its bearings in the same
direction: let this direction be that of the clock, when the apparatus
is viewed from above, then the motion of F will also have the same
direction, when viewed from the central vertical axis, as shown at F':
and let these directions be considered as positive. It is perfectly
clear that F will turn in its bearings, in the direction indicated, at
a rate precisely equal to that of the train-arm. Let P be a pointer
carried by F, and R a dial fixed to T; and let the pointer be vertical
when OO is the plane containing the axes of A, B, and E. Then, when F
has gone through any angle a measured from OO, the pointer will have
turned from its original vertical position through an equal angle, as
shown also at F'.
Now, there is no conceivable sense in which the motion of T can be
said to be added to the rotation of F about its axis, and the
expression "absolute revolution," as applied to the motion of the last
wheel in this train, is absolutely meaningless.
Nevertheless, Prof. Goodeve states (Elements of Mechanism, p. 165)
that "We may of course apply the general formula in the case of bevel
wheels just as in that of spur wheels." Let us try the experiment;
when the train-arm is stationary, and A released and turned to the
right, F turns to the left at the same rate, whence:
n
--- = -1; also m' = 0 when A is fixed,
m
and the equation becomes
n' - a
------ = -1, [therefore] n' = 2a:
- a
or in other words F turns _twice_ on its axis during one revolution of
T: a result too palpably absurd to require any comment. We have seen
that this identical result was obtained in the case of Fig. 15, and it
would, of course, be the same were the formula applied to Figs. 5 and
6; whereas it has never, so far as we are aware, been pretended that a
miter or a bevel wheel will make more than one rotation about its axis
in rolling once around an equal fixed one.
Again, if the formula be general, it should apply equally well to a
train of screw wheels: let us take, for example, the single pair shown
in Fig. 8, of which, when T is fixed, the velocity ratio is unity. The
directional relation, however, depends upon the direction in which the
wheels are twisted: so that in applying the formula, we shall have
_n/m_ = +1, if the helices of both wheels are right handed, and
_n_/_m_ = -1, if they are both left handed. Thus the formula leads to
the surprising conclusion, that when A is fixed and T revolves, the
planet-wheel B will revolve about its axis twice as fast as T moves,
in one case, while in the other it will not revolve at all.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
A favorite illustration of the peculiarities of epicyclic mechanism,
introduced both by Prof. Willis and Prof. Goodeve, is found in the
contrivance known as Ferguson's Mechanical Paradox, shown in Fig. 18.
This consists of a fixed sun-wheel A, engaging with a planet-wheel B
of the same diameter. Upon the shaft of B are secured the three thin
wheels E, G, I, each having 20 teeth, and in gear with the three
others F, H, K, which turn freely upon a stud fixed in the train-arm,
and have respectively 19, 20, and 21 teeth. In applying the general
formula, we have the following results:
n 20 n' - a 1
For the wheel F, --- = ---- = ---------, [therefore] n' = - ---- a.
m 19 -a 19
n n' - a
" " " H, --- = 1 = --------, [therefore] n' = 0.
m -a
n 20 n' - a 1
" " " K, --- = ---- = ---------, [therefore] n' = + ---- a.
m 21 -a 21
The paradoxical appearance, then, consists in this, that although the
drivers of the three last wheels each have the same number of teeth,
yet the central one, H, having a motion of circular translation,
remains always parallel to itself, and relatively to it the upper one
seems to turn in the same direction as the train-arm, and the lower in
the contrary direction. And the appearance is accepted, too, as a
reality; being explained, agreeably to the analysis just given, by
saying that H has no absolute rotation about its axis, while the other
wheels have; that of F being positive and that of K negative.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 18]
The Mechanical Paradox, it is clear, may be regarded as composed of
three separate trains, each of which is precisely like that of Fig.
16: and that, again, differs from the one of Fig. 15 only in the
addition of a third wheel. Now, we submit that the train shown in Fig.
17 is mechanically equivalent to that of Fig. 15; the velocity ratio
and the directional relation being the same in both. And if in Fig. 17
we remove the index P, and fix upon its shaft three wheels like E, G,
and I of Fig. 18, we shall have a combination mechanically equivalent
to Ferguson's Paradox, the three last wheels rotating in vertical
planes about horizontal axes. The relative motions of those three
wheels will be the same, obviously, as in Fig. 18; and according to
the formula their absolute motions are the same, and we are invited to
perceive that the central one does not rotate at all about its axis.
But it _does_ rotate, nevertheless; and this unquestioned fact is of
itself enough to show that there is something wrong with the formula
as applied to trains like those in question. What that something is,
we think, has been made clear by what precedes; since it is impossible
in any sense to add together motions which are unlike, it will be seen
that in order to obtain an intelligible result in cases like these,
the equation must be of the form _n'_/(_m'_ - _a_) = _n_/_m_. We shall
then have:
n 20 n' 20
For the wheel F, --- = ---- = ----, [therefore] n' = - ---- a;
m 19 -a 19
n n'
For the wheel H, --- = 1 = ----, [therefore] n' = -a;
m -a
n 20 n' 20
For the wheel K, --- = ---- = ----, [therefore] n' = - ---- a,
m 21 -a 21
which corresponds with the actual state of things; all three wheels
rotate in the same direction, the central one at the same rate as the
train arm, one a little more rapidly and the third a little more
slowly.
It is, then, absolutely necessary to make this modification in the
general formula, in order to apply it in determining the rotations of
any wheel of an epicyclic train whose axis is not parallel to that of
the sun-wheels. And in this modified form it applies equally well to
the original arrangement of Ferguson's paradox, if we abandon the
artificial distinction between "absolute" and "relative" rotations of
the planet-wheels, and regard a spur-wheel, like any other, as
rotating on its axis when it turns in its bearings; the action of the
device shown in Fig. 18 being thus explained by saying that the wheel
H turns once backward during each forward revolution of the train-arm,
while F turns a little more and K a little less than once, in the same
direction. In this way the classification and analysis of these
combinations are made more simple and consistent, and the
incongruities above pointed out are avoided; since, without regard to
the kind of gearing employed or the relative positions of the axes, we
have the two equations:
n' - a n
I. -------- = ---, for all complete trains;
m' - a m
n' n
II. -------- = ---, for all incomplete trains.
m' - a m
[Illustration: PLANETARY WHEEL TRAINS. Fig. 19]
As another example of the difference in the application of these
formulæ, let us take Watt's sun and planet wheels, Fig. 19. This
device, as is well known, was employed by the illustrious inventor as
a substitute for the crank, which some one had succeeded in patenting.
It consists merely of two wheels A and F connected by the link T; A
being keyed on the shaft of the engine and F being rigidly secured to
the connecting-rod. Suppose the rod to be of infinite length, so as to
remain always parallel to itself, and the two wheels to be of equal
size.
Then, according to Prof. Willis' analysis, we shall have--
n' - a n -s
-------- = --- = -1, n' = 0, [therefore] -------- = -1, whence
m' - a m m' - a
-a = a - m', or m = 2a.
The other view of the question is, that F turns once backward in its
bearings during each forward revolution of T; whence in Eq. 2 we
have--
n' n
-------- = --- = -1, n' = -a,
m' - a m
-a
[therefore] -------- -1, which gives -a = a - m', or m' = 2a,
m' - a
as before.
It is next to be remarked, that the errors which arise from applying
Eq. I. to incomplete trains may in some cases counterbalance and
neutralize each other, so that the final result is correct.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 20]
For example, take the combination shown in Fig. 20. This consists of a
train-arm T revolving about the vertical axis OO of the fixed wheel A,
which is equal in diameter to F, which receives its motion by the
intervention of one idle wheel carried by a stud S fixed in the arm.
The second train-arm T' is fixed to the shaft of F and turns with it;
A' is secured to the arm T, and F' is actuated by A' also through a
single idler carried by T'.
We have here a compound train, consisting of two simple planetary
trains, A--F and A'--F'; and its action is to be determined by
considering them separately. First suppose T' to be removed and find
the motion of F; next suppose F to be removed and T fixed, and find
the rotation of F'; and finally combine these results, noting that the
motion of T' is the same as that of F, and the motion of A' the same
as that of T.
Then, according to the analysis of Prof. Willis, we shall have
(substituting the symbol _t_ for _a_ in the equation of the second
train, in order to avoid confusion):
n n' - a
1. Train A--F. --- = 1 = --------; m' = 0,
m m' - a
n' - a
whence -------- = 1, n' = 0, = rot. of F.
a
n n' - t
2. Train A'--F'. --- = 1 = --------; m' = 0,
m m' - t
n' - t
whence again -------- = 1, t = 0, = rot. of F'.
-t
Of these results, the first is explicable as being the _absolute_
rotation of F, but the second is not; and it will be readily seen that
the former would have been equally absurd, had the axis LL been
inclined instead of vertical. But in either case we should find the
errors neutralized upon combining the two, for according to the theory
now under consideration, the wheel A', being fixed to T, turns once
upon its axis each time that train arm revolves, and in the same
direction; and the revolutions of T' equal the rotations of F, whence
finally in train A'--F' we have:
n n' - t
3. --- = 1 = --------; in which t = 0, m' = a,
m m' - t
n' - 0
which gives --------- = 1, or n' = a.
a - 0
This is, unquestionably, correct; and indeed it is quite obvious that
the effect upon F' is the same, whether we say that during a
revolution of T the wheel A' turns once forward and T' not at all, or
adopt the other view and assert that T' turns once backward and A' not
at all. But the latter view has the advantage of giving concordant
results when the trains are considered separately, and that without
regard to the relative positions of the axes or the kind of gearing
employed. Analyzing the action upon this hypothesis, we have:
In train A--F:
n n' n'
--- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -a;
m m' - a -a
In train A'--F':
n' n' n'
--- = 1 = --------; m' = 0, [therefore] ---- = 1, or n' = -t;
m m' - t -t
In combining, we have in the latter train m' = 0, t = -a, whence
n n' n'
--- = 1 = -------- gives ---- = 1, or n' = a, as before.
m m' - t +a
Now it happens that the only examples given by Prof. Willis of
incomplete trains in which the axis of a planet-wheel whose motion is
to be determined is not parallel to the central axis of the system,
are similar to the one just discussed; the wheel in question being
carried by a secondary train-arm which derives its motion from a wheel
of the primary train.
The application of his general equation in these cases gives results
which agree with observed facts; and it would seem that this
circumstance, in connection doubtless with the complexity of these
compound trains, led him to the too hasty conclusion that the formula
would hold true in all cases; although we are still left to wonder at
his overlooking the fact that in these very cases the "absolute" and
the "relative" rotations of the last wheel are identical.
[Illustration: PLANETARY WHEEL TRAINS. Fig. 21]
In Fig. 21 is shown a combination consisting also of two distinct
trains, in which, however, there is but one train-arm T turning freely
upon the horizontal shaft OO, to which shaft the wheels A', F, are
secured; the train-arm has two studs, upon which turn the idlers B B',
and also carries the bearings of the last wheel F'; the first wheel A
is annular, and fixed to the frame of the machine. Let it be required
to determine the results of one revolution of the crank H, the numbers
of teeth being assigned as follows:
A = 60, F = 30, A' = 60, F' = 10.
We shall then have, for the train ABF (Eq. I.),
n 60 n' - a
--- = - ---- = -2 = --------, in which n' = 1, m' = 0,
m 30 m' - a'
1 - a 1
whence -2 = -------, 2a = 1 - a, 3a = 1, a = ---.
-a 3
And for the train A'B'F' (Eq. II.),
n 60 n' 1
--- = ---- = 6 = --------, in which a = ---, m' = 1,
m 10 m' - a' 3
n'
whence 6 = -----------, or n' = 4.
1 - (1/3)
That is, the last wheel F' turns _four_ times about the axis LL during
one revolution of the crank H. But according to Profs. Willis and
Goodeve, we should have for the second train:
n 60 n' - a 1
--- = ---- = 6 = --------, in which a = ---, m' = 1,
m 10 m' - a' 3
n' - (1/3)
which gives 6 = -----------, n' - (1/3) = 4, n' = 4-1/3,
1 - (1/3)
or _four and one-third_ revolutions of F' for one of H.
This result, no doubt, might be near enough to the truth to serve all
practical purposes in the application of this mechanism to its
original object, which was that of paring apples, impaled upon the
fork K; but it can hardly be regarded as entirely satisfactory in a
general way; nor can the analysis which renders such a result
possible.
* * * * *
THE PANTANEMONE.
The need of irrigating prairies, inundating vines, drying marshes, and
accumulating electricity cheaply has, for some time past, led to a
search for some means of utilizing the forces of nature better than
has ever hitherto been done. Wind, which figures in the first rank as
a force, has thus far, with all the mills known to us, rendered
services that are much inferior to those that we have a right to
expect from it with improved apparatus; for the work produced,
whatever the velocity of the wind, has never been greater than that
that could be effected by wind of seven meters per second. But, thanks
to the experiments of recent years, we are now obtaining an effective
performance double that which we did with apparatus on the old system.
Desirous of making known the efforts that have been made in this
direction, we lately described Mr. Dumont's atmospheric turbine. In
speaking of this apparatus we stated that aerial motors generally stop
or are destroyed in high winds. Recently, Mr. Sanderson has
communicated to us the result of some experiments that he has been
making for years back by means of an apparatus which he styles a
pantanemone.
The engraving that we give of this machine shows merely a cabinet
model of it; and it goes without saying that it is simply designed to
exhibit the principle upon which its construction is based.
[Illustration: THE PANTANEMONE.]
Two plane surfaces in the form of semicircles are mounted at right
angles to each other upon a horizontal shaft, and at an angle of 45°
with respect to the latter. It results from this that the apparatus
will operate (even without being set) whatever be the direction of the
wind, except when it blows perpendicularly upon the axle, thus
permitting (owing to the impossibility of reducing the surfaces) of
three-score days more work per year being obtained than can be with
other mills. Three distinct apparatus have been successively
constructed. The first of these has been running for nine years in the
vicinity of Poissy, where it lifts about 40,000 liters of water to a
height of 20 meters every 24 hours, in a wind of a velocity of from 7
to 8 meters per second. The second raises about 150,000 liters of
water to the Villejuif reservoir, at a height of 10 meters, every 24
hours, in a wind of from 5 to 6 meters. The third supplies the
laboratory of the Montsouris observatory.
The first is not directible, the second may be directed by hand, and
the third is directed automatically. These three machines defied the
hurricane of the 26th of last January.--_La Nature._
* * * * *
RELVAS'S NEW LIFE-BOAT.
The Spanish and Portuguese papers have recently made known some
interesting experiments that have been made by Mr. Carlos Relvas with
a new life-boat which parts the waves with great facility and exhibits
remarkable stability. This boat, which is shown in front view in one
of the corners of our engraving, is T-shaped, and consists of a very
thin keel connected with the side-timbers by iron rods. Cushions of
cork and canvas are adapted to the upper part, and, when the boat is
on the sea, it has the appearance of an ordinary canoe, although, as
may be seen, it differs essentially therefrom in the submerged part.
When the sea is heavy, says Mr. Relvas, and the high waves are
tumbling over each other, they pass over my boat, and are powerless to
capsize it. My boat clears waves that others are obliged to recoil
before. It has the advantage of being able to move forward, whatever
be the fury of the sea, and is capable, besides, of approaching rocks
without any danger of its being broken.
[Illustration: RELVAS'S NEW LIFE BOAT.]
A committee was appointed by the Portuguese government to examine this
new life-boat, and comparative experiments were made with it and an
ordinary life-boat at Porto on a very rough sea. Mr. Relvas's boat was
manned by eight rowers all provided with cork girdles, while the
government life-boat was manned by twelve rowers and a pilot, all
likewise wearing cork girdles. The chief of the maritime department,
an engineer of the Portuguese navy and a Portuguese deputy were
present at the trial in a pilot boat. The three boats proceeded to the
entrance of the bar, where the sea was roughest, and numerous
spectators collected upon the shore and wharfs followed their
evolutions from afar.
The experiments began at half past three o'clock in the afternoon. The
two life-boats shot forward to seek the most furious waves, and were
seen from afar to surmount the billows and then suddenly disappear. It
was a spectacle as moving as it was curious. It was observed that Mr.
Relvas's boat cleft the waves, while the other floated upon their
surface like a nut-shell. After an hour's navigation the two boats
returned to their starting point.
The official committee that presided over these experiments has again
found in this new boat decided advantages, and has pointed out to its
inventor a few slight modifications that will render it still more
efficient.--_La Nature._
* * * * *
EXPERIMENTS WITH DOUBLE-BARRELED GUNS AND RIFLES.
The series of experiments we are about to describe has recently been
made by Mr. Horatio Phillips, a practical gun maker of London. The
results will no doubt prove of interest to those concerned in the use
or manufacture of firearms.
The reason that the two barrels of a shot gun or rifle will, if put
together parallel, throw their charges in diverging lines has never
yet been satisfactorily accounted for, although many plausible and
ingenious theories have been advanced for the purpose. The natural
supposition would be that this divergence resulted from the axes of
the barrels not being in the same vertical plane as the center line of
the stock. That this is not the true explanation of the fact, the
following experiment would tend to prove.
[Illustration: EXPERIMENTS WITH DOUBLE-BARRELLED GUNS.]
Fig. 1 represents a single barrel fitted with sights and firmly
attached to a heavy block of beech. This was placed on an ordinary
rifle rest, being fastened thereto by a pin at the corner, A, the
block and barrel being free to revolve upon the pin as a center.
Several shots were fired both with the pin in position and with it
removed, the barrel being carefully pointed at the target each time.
No practical difference in the accuracy of fire was discernible under
either condition. When the pin was holding the corner of the block,
the recoil caused the barrel to move from right to left in a circular
path; but when the pin was removed, so that the block was not attached
to the rest in any way, the recoil took place in a line with the axis
of the bore. It will be observed that the conditions which are present
when a double barreled gun is fired in the ordinary way from the
shoulder were in some respects much exaggerated in the apparatus, for
the pin was a distance of 3 in. laterally from the axis of the barrel,
whereas the center of resistance of the stock of a gun against the
shoulder would ordinarily be about one-sixth of this distance from the
axis of the barrel. This experiment would apparently tend to prove
that the recoil does not appreciably affect the path of the
projectile, as it would seem that the latter must clear the muzzle
before any considerable movement of the barrel takes place.
With a view to obtain a further confirmation of the result of this
experiment, it was repeated in a different form by a number of shots
being fired from a "cross-eyed" rifle,[1] in which the sights were
fixed in the center of the rib. Very accurate shooting was obtained
with this arm.
[Footnote 1: A cross-eyed rifle is one made with a crooked stock
for the purpose of shooting from the right shoulder, aim being
taken with the left eye.]
A second theory, often broached, in order to account for the
divergence of the charge, is that the barrel which is not being fired,
by its _vis inertia_ in some way causes the shot to diverge. In order
to test this, Mr. Phillips took a single rifle and secured it near the
muzzle to a heavy block of metal, when the accuracy of the shooting
was in no way impaired.
So far the experiments were of a negative character, and the next step
was made with a view to discover the actual cause of the divergence
referred to. A single barrel was now taken, to which a template was
fitted, in order to record its exact length. The barrel was then
subjected to a heavy internal hydrostatic pressure. Under this
treatment it expanded circumferentially and at the same time was
reduced in length. This, it was considered, gave a clew to the
solution of the problem. A pair of barrels was now taken and a
template fitted accurately to the side of the right-hand one. As the
template fitted the barrel when the latter was not subject to internal
pressure, upon such pressure being applied any alterations that might
ensue in the length or contour of the barrel could be duly noted. The
right-hand barrel was then subjected to internal hydrostatic pressure.
The result is shown in an exaggerated form in Fig. 2. It will be seen
that both barrels are bent into an arched form. This would be caused
by the barrel under pressure becoming extended circumferentially, and
thereby reduced in length, because the metal that is required to
supply the increased circumference is taken to some extent from the
length, although the substance of metal in the walls of the barrel by
its expansion contributes also to the increased diameter. A simple
illustration of this effect is supplied by subjecting an India-rubber
tube to internal pressure. Supposing the material to be sufficiently
elastic and the pressure strong enough, the tube would ultimately
assume a spherical form. It is a well known fact that heavy barrels
with light charges give less divergence than light barrels with heavy
charges.
After the above experiments it was hoped that, if a pair of barrels
were put together parallel and soldered only for a space of 3 in. at
the breech end, and were then coupled by two encircling rings joined
together as in Fig. 4, the left-hand ring only being soldered to the
barrel, very accurate shooting would be obtained. For, it was argued,
that by these means the barrel under fire would be able to contract
without affecting or being affected by the other barrel; that on the
right-hand, it will be seen by the illustration, was the one to slide
in its ring.
A pair of able 0.500 bore express rifle barrels were accordingly
fitted in this way. Fig. 3 shows the arrangement with the rings in
position. Upon firing these barrels with ordinary express charges it
was found that the lines of fire from each barrel respectively crossed
each other, the bullet from the right-hand barrel striking the target
10 in. to the left of the bull's eye, while the left barrel placed its
projectile a similar distance in the opposite direction; or, as would
be technically said, the barrels crossed 20 in. at 100 yards, the
latter distance being the range at which the experiment was made.
These last results have been accounted for in the following manner:
The two barrels were rigidly joined for a space of 3 in., and for that
distance they would behave in a manner similar to that illustrated in
Fig. 2, and were they not coupled at the muzzles by the connecting
rings they would shoot very wide, the charges taking diverging
courses. When the connecting rings are fitted on, the barrel not being
fired will remain practically straight, and, as it is coupled to the
barrel being fired by the rings, the muzzle of the latter will be
restrained from pointing outward.
The result will be as shown in an exaggerated manner by the dotted
lines on the right barrel in Fig. 3.
It would appear from these experiments that when very accurate
shooting is required at long ranges with double-barreled rifles, they
should be mounted in a manner similar to that adopted in the
manufacture of the Nordenfelt machine gun, in which weapon the barrels
are fitted into a plate at the extreme breech end, the muzzles
projecting through holes bored to receive them in a metal plate. No
unequal expansion would then take place, and the barrels would be free
to become shorter independently of each other. We give the above
experiments on the authority of their author, who, we believe, has
taken great pains to render them as exhaustive as possible, so far as
they go.--_Engineering._
* * * * *
BALL TURNING MACHINE.
The distinguishing feature in the ball turning machine shown opposite
is that the tool is stationary, while the work revolves in two
directions simultaneously. In the case of an ordinary spherical
object, such as brass clack ball, the casting is made from a perfect
pattern having two small caps or shanks, in which the centers are also
marked to avoid centering by hand. It is fixed in the machine between
two centers carried on a face plate or chuck, with which they revolve.
One of these centers, when the machine is in motion, receives a
continuous rotary motion about its axis from a wormwheel, D. This is
driven by a worm, C, carried on a shaft at the back of the chuck, and
driven itself by a wormwheel, B, which gears with a screw which rides
loosely upon the mandrel, and is kept from rotating by a finger on the
headstock. This center, in its rotation, carries with it the ball,
which is thus slowly moved round an axis parallel to the face plate,
at the same time that it revolves about the axis of the mandrel, the
result being that the tool cuts upon the ball a scroll, of which each
convolution is approximately a circle, and lies in a plane parallel to
the line of centers.
When the chuck is set for one size of ball, which may be done in a few
minutes, any quantity of that diameter may be turned without further
adjustment. A roughing cut for a 2 in. ball may be done in one minute,
and a finishing cut leaving the ball quite bright in the same time.
The two paps are cut off within one-sixteenth of an inch and then
broken off, and the ball finished in the usual way. On account of the
work being geometrically true, the finishing by the ferrule tool is
done in one quarter of the time usually required.
[Illustration: IMPROVED BALL TURNING MACHINE.]
The chuck may be applied to an ordinary lathe or may be combined with
a special machine tool, as show in our illustration. In the latter
case everything is arranged in the most handy way for rapid working,
and six brass balls of 2 in. in diameter can be turned and finished in
an hour. The machine is specially adapted for turning ball valves for
pumps, pulsometers, and the like, and in the larger sizes for turning
governor balls and spherical nuts for armor plates, and is
manufactured by Messrs. Wilkinson and Lister, of Bradford Road Iron
Works, Keighley.--_Engineering._
* * * * *
COOLING APPARATUS FOR INJECTION WATER.
It often happens in towns and where manufactories are crowded
together, that the supply of water for condensing purposes is very
small, and consequently that it attains an inconveniently high
temperature under unfavorable conditions of weather, resulting in the
deterioration of the vacuum and a consequent increase in the
consumption of fuel. To remedy or to diminish this difficulty, Messrs.
Boase and Miller, of London, have brought out the water cooler
illustrated above. This consists, says _Engineering_, of a revolving
basket of wire gauze surrounding an inner stationary vessel pierced
with numerous small holes, through which the heated water discharged
by the air pump finds its way into the basket, to be thrown out in the
form of fine spray to a distance of 20 ft. at each side. The drops are
received in the tank or pond, and in their rapid passage through the
air are sufficiently cooled to be again injected into the condenser.
The illustration shows a cooler having a basket three feet in
diameter, revolving at 300 revolutions per minute, and discharging
into a tank 40 ft. square. It requires 3 to 4 indicated horse-power to
drive it, and will cool 300 gallons per minute. The following decrease
of temperature has been observed in actual practice: Water entering at
95 deg. fell 20 deg. in temperature; water entering at 100 deg. to 110
deg. fell 25 deg.; and water entering at 110 deg. to 120 deg. fell 30
deg. The machine with which these trials were made was so placed that
the top of the basket was four ft. from the surface of the water in
the pond. With a greater elevation, as shown in the engraving, better
results can be obtained.
[Illustration: IMPROVED WATER COOLING APPARATUS.]
The advantages claimed for the cooler are that by its means the
temperature of the injection water can be reduced, the cost and size
of cooling ponds can be diminished, and condensing engines can be
employed where hitherto they have not been possible. The apparatus has
been for two years in operation at several large factories, and there
is every reason to believe that its use will extend, as it supplies a
real want in a very simple and ingenious manner. Messrs. Duncan
Brothers, of Dundee and 32 Queen Victoria Street, E.C., are the
manufacturers.
* * * * *
CORRUGATED DISK PULLEYS.
This is a pulley recently introduced by Messrs. J. and E. Hall, of
Dartford Eng. With the exception of the boss, which is cast, it is
composed entirely of steel or sheet iron. In place of the usual arms a
continuous web of corrugated sheet metal connects the boss to the rim;
this web is attached to the boss by means of Spence's metal. Inside
the rim, which is flanged inward, a double hoop iron ring is fixed for
strengthening purposes. The advantageous disposition of metal obtained
by means of the corrugated web enables the pulley to be made of a
given strength with less weight of material, and from this cause and
also on account of being accurately balanced these pulleys are well
adapted for high speeds.
[Illustration]
* * * * *
[KANSAS CITY REVIEW.]
EARLY HISTORY OF THE TELEGRAPH.
Although the electric telegraph is, comparatively speaking, a recent
invention, yet methods of communication at a distance, by means of
signals, have probably existed in all ages and in all nations. There
is reason to believe that among the Greeks a system of telegraphy was
in use, as the burning of Troy was certainly known in Greece very soon
after it happened, and before any person had returned from Troy.
Polybius names the different instruments used by the ancients for
communicating information--"pyrsia," because the signals were always
made by means of fire lights. At first they communicated information
of events in an imperfect manner, but a new method was invented by
Cleoxenus, which was much improved by Polybius, as he himself informs
us, and which may be described as follows:
Take the letters of the alphabet and arrange them on a board in five
columns, each column containing five letters; then the man who signals
would hold up with his left hand a number of torches which would
represent the number of the column from which the letter is to be
taken, and with his right hand a number of torches that will represent
the particular letter in that column that is to be taken. It is thus
easy to understand how the letters of a short sentence are
communicated from station to station as far as required. This is the
pyrsia or telegraph of Polybius.
It seems that the Romans had a method of telegraphing in their walled
cities, either by a hollow formed in the masonry, or by a tube fixed
thereto so as to confine the sound, in order to convey information to
any part they liked. This method of communicating is in the present
age frequently employed in the well known speaking tubes. It does not
appear that the moderns had thought of such a thing as a telegraph
until 1661, when the Marquis of Worcester, in his "Century of
Inventions," affirmed that he had discovered a method by which a man
could hold discourse with his correspondent as far as they could
reach, by night as well as by day; he did not, however, describe this
invention.
Dr. Hooke delivered a discourse before the Royal Society in 1684,
showing how to communicate at great distances. In this discourse he
asserts the possibility of conveying intelligence from one place to
another at a distance of 120 miles as rapidly as a man can write what
he would have sent. He takes to his aid the then recent invention of
the telescope, and explains how characters exposed at one station on
the top of one hill may be made visible to the next station on the top
of the next hill. He invented twenty-four simple characters, each
formed of a combination of three deal boards, each character
representing a letter by the use of cords; these characters were
pushed from behind a screen and exposed, and then withdrawn behind the
screen again. It was not, however, until the French revolution that
the telegraph was applied to practical purposes; but about the end of
1703 telegraphic communication was established between Paris and the
frontiers, and shortly afterward telegraphs were introduced into
England.
The history of the invention and introduction of the electric
telegraph by Prof. Morse is one of inexhaustible interest, and every
incident relating to it is worthy of preservation. The incidents
described below will be found of special interest. The article is from
the pen of the late Judge Neilson Poe, and was the last paper written
by him. He prepared it during his recent illness, the letter embodied
in it from Mr. Latrobe being of course obtained at the time of its
date. It is as follows:
On the 5th of April, 1843, when the monthly meeting of the directors
of the Baltimore & Ohio Railroad Company was about to adjourn, the
President, the Hon. Louis McLane, rose with a paper in his hand which
he said he had almost overlooked, and which the Secretary would read.
It proved to be an application from Prof. Morse for the privilege of
laying the wires of his electric telegraph along the line of the
railroad between Baltimore and Washington, and was accompanied by a
communication from B.H. Latrobe, Esq., Chief Engineer, recommending
the project as worthy of encouragement.
On motion of John Spear Nicholas, seconded by the Hon. John P.
Kennedy, the following resolution was then considered:
_Resolved_, "That the President be authorized to afford Mr. Morse such
facilities as may be requisite to give his invention a proper trial
upon the Washington road, provided in his opinion and in that of the
engineer it can be done without injury to the road and without
embarrassment to the operations of the company, and provided Mr. Morse
will concede to the company the use of the telegraph upon the road
without expense, and reserving to the company the right of
discontinuing the use if, _upon experiment_, it should prove _in any
manner injurious_."
"Whatever," said Mr. McLane, "may be our individual opinions as to the
feasibility of Mr. Morse's invention, it seems to me that it is our
duty to concede to him the privilege he asks, and to lend him all the
aid in our power, especially as the resolution carefully protects the
company against all present or future injury to its works, and secures
us the right of requiring its removal at any time."
[In view of the fact that no railroad can now be run safely without
the aid of the telegraph, the cautious care with which the right to
remove it if it should become a nuisance was reserved, strikes one at
this day as nearly ludicrous.]
A short pause ensued, and the assent of the company was about to be
assumed, when one of the older directors, famed for the vigilance with
which he watched even the most trivial measure, begged to be heard.
He admitted that the rights and interests of the work were all
carefully guarded by the terms of the resolution, and that the company
was not called upon to lay out any of its means for the promotion of
the scheme. But notwithstanding all this, he did not feel, as a
conscientious man, that he could, without further examination, give
his vote for the resolution. He knew that this idea of Mr. Morse,
however plausible it might appear to theorists and dreamers, and
so-called men of science, was regarded by all practical people as
destined, like many other similar projects, to certain failure, and
must consequently result in loss and possibly ruin to Mr. Morse. For
one, he felt conscientiously scrupulous in giving a vote which would
aid or tempt a visionary enthusiast to ruin himself.
Fortunately, the views of this cautious, practical man did not
prevail. A few words from the mover of the resolution, Mr. Nicholas,
who still lives to behold the wonders he helped to create, and from
Mr. Kennedy, without whose aid the appropriation would not have passed
the House of Representatives, relieved the other directors from all
fear of contributing to Mr. Morse's ruin, and the resolution was
adopted. Of the President and thirty directors who took part in this
transaction, only three, Samuel W. Smith, John Spear Nicholas, and the
writer, survive. Under it Morse at once entered upon that test of his
invention whose fruits are now enjoyed by the people of all the
continents.
It was not, however, until the spring of 1844 that he had his line and
its appointments in such a condition as to allow the transmission of
messages between the two cities, and it was in May of that year that
the incident occurred which has chiefly led to the writing of this
paper.
MR. LATROBE'S RECOLLECTIONS.
MY DEAR MR. POE: Agreeably to my promise, this morning I put
on paper my recollection of the introduction of the magnetic telegraph
between Baltimore and Washington. I was counsel of the Baltimore &
Ohio Railroad Co. at the time, and calling on Mr. Louis McLane, the
President, on some professional matter, was asked in the course of
conversation whether I knew anything about an electric telegraph which
the inventor, who had obtained an appropriation from Congress, wanted
to lay down on the Washington branch of the road. He said he expected
Mr. Morse, the inventor, to call on him, when he would introduce me to
him, and would be glad if I took an opportunity to go over the subject
with him and afterward let him, Mr. McLane, know what I thought about
it. While we were yet speaking, Mr. Morse made his appearance, and
when Mr. McLane introduced me he referred to the fact that, as I had
been educated at West Point, I might the more readily understand the
scientific bearings of Mr. Morse's invention. The President's office
being no place for prolonged conversation, it was agreed that Mr.
Morse should take tea at my dwelling, when we would go over the whole
subject. We met accordingly, and it was late in the night before we
parted. Mr. Morse went over the history of his invention from the
beginning with an interest and enthusiasm that had survived the
wearying toil of an application to Congress, and with the aid of
diagrams drawn on the instant made me master of the matter, and wrote
for me the telegraphic alphabet which is still in use over the world.
Not a small part of what Mr. Morse said on this occasion had reference
to the future of his invention, its influence upon communities and
individuals, and I remember regarding as the wild speculations of an
active imagination what he prophesied in this connection, and which I
have lived to see even more than realized. Nor was his conversation
confined to his invention. A distinguished artist, an educated
gentleman, an observant traveler, it was delightful to hear him talk,
and at this late day I recall few more pleasant evenings than the only
one I passed in his company.
Of course, my first visit the next morning was to Mr. McLane to make
my report. By this time I had become almost as enthusiastic as Mr.
Morse himself, and repeated what had passed between us. I soon saw
that Mr. McLane was becoming as eager for the construction of the line
to Washington as Mr. Morse could desire. He entered warmly into the
spirit of the thing, and laughed heartily, if not incredulously, when
I told him that although he had been Minister to England, Secretary of
State, and Secretary of the Treasury, his name would be forgotten,
while that of Morse would never cease to be remembered with gratitude
and praise. We then considered the question as to the right of the
company to permit the line to be laid in the bed of the road--the plan
of construction at that time being to bury in a trench some eight or
ten inches deep a half inch leaden tube containing the wrapped wire
that was to form the electric circuit. About this there was, in my
opinion, no doubt, and it was not long after that the work of
construction commenced. I met Mr. Morse from time to time while he
lived, and often recurred to the evening's discussion at my house in
Baltimore.
The above is the substance of what I have more than once related to
other persons. I hope you will persist in your design of putting on
paper your own very interesting recollections in this connection, and
if what I have contributed of mine is of service to you, I shall be
much pleased.
Most truly yours,
JOHN H.B. LATROBE.
March 3, 1881.
* * * * *
THE KRAVOGL ELECTRIC MOTOR.
At the origin of every science, of whatever nature it may be, there is
always a fruitless period, of greater or less length, characterized by
the warfare of a few superior minds against general apathy. The finest
discoveries pass unperceived, so to speak, since they cannot cross the
limits of a narrow circle; and it often happens that they fall into
oblivion before they have been seriously judged. Meanwhile, a slow
progress is imperceptibly made, and, in measure as theoretical
principles more clearly disengage themselves, a few industrial
applications spring up and have the effect of awakening curiosity. An
impulse is thus given, and from this moment a movement in advance goes
on increasing at a headlong pace from day to day.
With electricity this period has been of comparatively short duration,
since scarcely a century and a half separate us from the first
experiments made in this line of research. Now that it has truly taken
its place in a rank with the other sciences, we like to go back to the
hesitations of the first hour, and trace, step by step, the history of
the progress made, so as to assign to each one that portion of the
merit that belongs to him in the common work. When we thus cast a
retrospective glance we find ourselves in the presence of one strange
fact, and that is the simultaneousness of discoveries. That an
absolutely original idea, fertile in practical consequences, should
rise at a given moment in a fine brain is well; we admire the
discovery, and, in spite of us, a little surprise mingles with our
admiration. But is it not a truly curious thing that _several_
individuals should have had at nearly the same time that idea that was
so astonishing in one? This, however, is a fact that the history of
electrical inventions offers more than one example of. No one ignores
the fact that the invention of the telephone gave rise to a notorious
lawsuit, two inventors having had this ingenious apparatus patented on
the same day and at nearly the same hour. This is one example among a
thousand. In the history of dynamo-electric machines it is an equally
delicate matter to fix upon the one to whom belongs the honor of
having first clearly conceived the possibility of engendering
continuous currents.
We do not wish to take up this debate nor to go over the history of
the question again. Every one knows that the first continuous current
electric generator whose form was practical is due to Zenobius Gramme,
and dates back to July, 1871, an epoch at which appeared a memoir
(entitled "Note upon a magneto-electric machine that produces
continuous currents") that was read to the Academy of Sciences by Mr.
Jamin. Ten years previous, Pacinotti had had a glimpse of the
phenomenon, and of its practical realization, but was unfortunately
unable to appreciate the importance of his discovery and the benefit
that might be reaped from it. It is of slight consequence whether
Gramme knew of this experiment or not, for the glory that attaches to
his name could not be diminished for all that. But an interesting fact
that we propose to dwell upon now has recently been brought to light
in an electrical review published at Vienna.[1] It results from
documents whose authenticity cannot be doubted that, as far back as
1867, Mr. L. Pfaundler, a professor at Innsbruck, very clearly
announced the reversibility of a magneto-electric motor constructed by
Kravogl, a mechanician of the same place, and that he succeeded some
time before Gramme in obtaining continuous currents.
[Footnote 1: _Zeitschrift des Electrotechnischen Vereines_ in
_Wien_, July, 1883.]
The Kravogl motor that figured at the Universal Exhibition of 1867 is
but little known, and it is now very difficult to obtain drawings of
it. What is certain is that this motor is an application of the
properties of the solenoid, and, from this standpoint, resembles the
Bessolo motor that was patented in 1855. We may figure the apparatus
to our mind very well if we suppose that in the Gramme ring a half and
almost two-thirds of the core are removed, and the spirals are movable
around the said core. If a current be sent into a portion of the
spirals only, and in such a way that only half of the core be exposed,
the latter will move with respect to the bobbin or the bobbin with
respect to the core, according as we suppose the solenoid or the
bobbin fixed. In the first case we have a Bessolo motor, and in the
second a Kravogl one.
In order to obtain a continuous motion it is only necessary to allow
the current to circulate successively in the different portions of the
solenoid. It is difficult to keep the core in place, since it is
unreachable, being placed in the interior of the bobbin. Kravogl
solved this difficulty by constructing a hollow core into which he
poured melted lead. This heavy piece, mounted upon rollers, assumed a
position of equilibrium that resulted from its weight, from friction,
and from magnetic attraction. But for a current of given intensity
this position, once reached, did not vary, and so necessitated a
simple adjustment of the rubbers. Under such circumstances, with a
somewhat large number of sections, the polarity of the core was nearly
constant. The spirals as a whole were attached to a soft iron armature
that had the effect of closing up the lines of forces and forming a
shell, so to speak.
Like Bessolo, Kravogl never thought of making anything but a motor,
and did not perceive that his machine was reversible. It results from
some correspondence between Dr. A. Von Waltenhofen and Mr. L.
Pfaundler at this epoch that the latter clearly saw the possibility of
utilizing this motor as a current generator. Under date of November 9,
1867, he wrote, in speaking of the Kravogl motor, which had just been
taken to Innsbruck in order to send it to Paris. "I regret that I
shall not be able to see it any more, for I should have liked to try
to make it act in an opposite direction, that is to say, to produce a
current or an electric light by means of mechanical work." A little
more than two years later these experiments were carried out on a
larger motor constructed by Kravogl in 1869, and Mr. Pfaundler was
enabled to write as follows: "Upon running the machine by hand we
obtain a current whose energy is that of one Bunsen element." This
letter is dated February 11, 1870, that is to say, it is a year
anterior to the note of Gramme.
[Illustration: FIG. 1.]
In the presence of the historic interest that attaches to the
question, we do not think it will be out of place to reproduce here
the considerations that guided Prof. Pfaundler in the researches that
led him to convert the Kravogl motor into a dynamo-electric machine.
Let us consider two magnetized bars, _db_ and _bd'_, placed end to end
and surrounded by a cylindrical armature forming a shell, this
armature being likewise supposed to be a permanent magnet and to
present poles of contrary direction opposite the poles of the bars.
For the sake of greater simplicity this shell is represented by a part
only in the figure, _s n n s_. If, into a magnetic field thus
formed, we pass a spiral from left to right, the spiral will be
traversed by a current whose direction will change according to the
way in which the moving is done. It is only necessary to apply Lenz's
law to see that a reversal of the currents will occur at the points,
_a_ and _c_, the direction of the current being represented by arrows
in the figure. If we suppose a continual displacement of the spirals
from left to right, we shall collect a continuous current by placing
two rubbers at _a_ and _c_. Either the core or the shell may be
replaced by a piece of soft iron. In such a case this piece will move
with the spiral and keep its poles that are developed by induction
fixed in space. From this, in order to reach a dynamo-electric machine
it is necessary to try to develop the energy of the magnetic field by
the action of the current itself. If we suppose the core to be of soft
iron, and make a closer study of the action of the current as regards
the polarity that occurs under the influence of the poles, _s_, _n_,
_s_, we shall see that from _d_ to _a_ and from _b_ to _c_ the current
is contrary, while that from _a_ to _b_ and from _c_ to _d'_ it is
favorable to the development of such polarity. In short, with a spiral
moving from _d_ to _d'_ the resulting effect is _nil_, a fact,
moreover, that is self-evident. Under such circumstances, if we
suppose the shell, as well as the core, to be of soft iron, we shall
obtain a feeble current due to the presence of remanent magnetism; but
this magnetism will not be able to continue increasing under the
influence of the current. To solve this difficulty two means present
themselves: (1) to cause a, favorable magnetic current and act upon
the armature, and (2) to suppress such portions of the current in the
spirals as are injurious in effect. The first solution was thought of
by Gramme in 1871, and is represented diagramatically in Fig. 2. The
second is due to Prof. Pfaundler, and dates back to 1870. The core is
cut through the center (Fig. 3), and the portion to the right is
suppressed; the current is interrupted between _da_ and _cd'_, and is
closed only between _a_ and _c_ (_v_, Fig. 1). It results from this
arrangement that, under the action of the current, the polarity due to
remanent magnetism does nothing but increase. It suffices then for but
little remanent magnetism to prime the machine; the polarity of the
shell continues to increase, and the energy of the magnetic field, and
consequently of the current, has for a limit only the saturation of
the soft iron. If, now, we curve the core, the spirals, and the
armature into a circle, we have a Gramme or a Pfaundler machine,
according as we consider Fig. 2 or Fig. 3.
[Illustration: FIG. 2.]
[Illustration: FIG. 3.]
This latter apparatus has in this case the form shown in Fig. 4.
[Illustration: FIG. 4.]
The spiral, _s m b_, is movable, and the core, N _o s_, is kept in a
position of equilibrium by virtue of its weight, and is provided with
rollers. For the sake of greater clearness, the front part of the
armature is supposed to be removed. The current does not circulate in
the spirals to the right of the diameter, W O, which latter is not
absolutely vertical. The position of the rubbers and armature is
regulated once for all. We do not know just what were the means
devised by Kravogl to suppress the current in the spheres to the
right. At all events, it is probable that the system has grown old
since Gramme invented his collector. In the application of the Kravogl
motor to the generation of continuous currents, Professor Pfaundler
now proposes to ingeniously utilize the Gramme collector. In such a
case the arrangement shown in Fig. 5 would be adopted. Let us suppose
an ordinary collector having as many plates as there are sections in
the ring, these plates being connected as usual with the entrance and
exit wires of the sections. The diametrically opposite touches that
are in the line, W O, are divided, and one of the halves is connected
at the entrance, _c a'_ (Fig. 4), with the corresponding section,
while the other communicates with the exit, _c' a_, of the neighboring
section. Each of these halves is prolonged by a piece of metal bent
into the form of an arc of a circle and embracing a little less than a
semi-circumference. Between these prolongations there is an insulating
part. In the rotary motion of the spiral, at least one of the touches
is always outside of the arc comprised between the brushes, R. In
order to secure a continuity of the circuit in the effective arc, W S_ o_,
it is only necessary to arrange a rubber, M, in such a way as to
establish a communication between the two parts of the divided touch
as soon as this latter enters the arc under consideration.
In order to produce a current in the direction of the arrows shown in
Fig. 4, the spiral and axle must revolve from right to left. In this
case the rubber, M, occupies the position shown in the same figure,
the brushes embracing an arc of a little less than 180°. As soon as
the lower touch comes in contact with the brush, R, when the
revolution is being effected from left to right, the rubber, M,
establishes a communication between the two halves that have until now
been isolated, and the current is no longer interrupted. The second
touch during this time is at any point whatever of the arc, W N _o_,
and the spirals corresponding to the latter arc outside of the
circuit. In short, thanks to the rubber, M, we have an ordinary Gramme
collector in that portion of the circuit comprised between the
brushes, and a collector with a breakage of the circuit in the portion
to the right.
[Illustration: FIG. 5.]
This type of machine is entirely theoretical. In the apparatus used
for Prof. Pfaundler's experiments in 1870, the armature revolved with
the solenoid. The core and armature were of soft iron, and the core
was arranged in a manner analogous to the preceding, and remained in
place under the action of its weight, and the shell, forming a
complete circle, revolved with poles fixed in space.
Practically, the machine that we have just described would prove
inconvenient to realize, and would present serious inconveniences. In
the first place, it seems to us quite difficult to transmit the motion
of the solenoid to the axle, supposing the former to revolve within
the armature. In the second place, considerable friction would surely
occur between the spirals and core, and the axle, being submitted to a
lateral stress, would be placed in a poor condition for work. It is
even allowable to doubt whether such a type could be practically got
up. At all events, no trial has as yet been made of it.
Compared with the Gramme machine, from an absolutely theoretical point
of view, the Pfaundler apparatus presents undoubted advantages. A
theoretically perfect dynamo electric machine would be one in which
there was a complete reciprocity between the magnetizing action of the
current and the inductive action of the magnetic field. Now, such is
not the case in the Gramme machine. In this apparatus the soft iron
core is at the same time a magnet through favorable induction and a
disadvantageous electro-magnet. This double polarization is only
remedied to a certain extent by the adjustment of the brushes. In the
Pfaundler machine, on the contrary, the electro-magnetism and
magnetism through induction act in the same direction, and concur in
effecting a polarization that favors the production of the current.
Looked at it in this light, the latter machine more nearly approaches
the type of perfection than does that of Gramme.
But we must not forget that such qualities are purely theoretical. In
practice the best machine is that in which the copper is best
utilized, that is to say, that which with a given weight of this metal
furnishes the most work. Now, this is certainly not the case in the
Pfaundler machine, for here half or more than half of the ring is
inert--a defect which is apparent at first sight. It results from this
that as soon as we propose to obtain an electromotive force, however
slight it be, we must get it with machines of large dimensions. Now,
it is permissible to believe that under such circumstances (taking
into consideration the complication of mechanical means that the
construction of such apparatus necessitates, and the great friction
that occurs) it would be impossible to obtain practical rotary
velocities. Comparing his machine with Gramme's, Prof. Pfaundler
expresses the idea that between them there is the same analogy as
there is between a constant pressure and an expansion engine. With
cylinders of equal diameters the work performed by the former of these
is greater than that done by the second, but in the latter the
expansive force of the steam is better utilized. This comparison seems
to us to be more ingenious than exact. Would it not be coming nearer
to the truth if we were to suppose a case of a hydraulic motor whose
performance continued diminishing with the height of the fall, and
would it not be advantageous under such circumstances to utilize only
a portion of the fall for the purpose of increasing the motor's
performance?
This machine, however, as before stated, has never as yet been
constructed, so that experimental data relative to its mode of working
are wanting. It is especially interesting as regards its origin, which
dates back to an epoch at which researches on the dynamo electric
machine were at their heat. It is in its historical aspect that it is
proper to regard it, and it is from such a point of view that we have
deemed it well to say a few words about it in this place.--_La Lumiere
Electrique._
* * * * *
BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.
We shall not attempt to pass in review the several apparatus that have
hitherto been devised for igniting blasts in mining operations, but
shall simply describe in this place a machine recently invented for
this purpose by Mr. Bornhardt, an engineer to the Grand Duke of
Brunswick.
This apparatus (shown in the accompanying engravings) consists
essentially of two hard-rubber disks, A (Figs. 2 and 3), keyed to an
iron axle, and of two rubbers, B, that are formed of skin and are held
against the disks by small springs, R; motion is communicated to the
axle, _a_, by means of a pair of gearings, _a_ and _b_, and a crank,
_f_.
[Illustration: BORNHARDT'S ELECTRIC MACHINE FOR BLASTING IN MINES.]
Each disk revolves between two metallic rings, _c_, provided with
points that attract and collect in Leyden jars, D, the electricity
produced by the friction. For discharging the condensers there is
employed a manipulator formed of a rod, mm, which can be acted upon,
from the exterior, by means of a button, _k_. Upon bringing the ball,
_m_, of the rod in contact with the ball, _p_, of the condenser, the
lever (which then takes the position shown by the dotted line)
continues to remain in connection with a small ring, _q_, through a
special spring. Another ring, _t_, is connected in the same way with
the external armature of the condenser. Upon connecting the rings, _p_
and _t_, by a wire to which cartridges are attached, any number of the
latter may be ignited.
The parts that we have just enumerated are inclosed in a tin box
covered with a wooden casing, P. Between the two there is inserted a
sheet of hard rubber in order to prevent a loss of electricity; the
whole is held in place by strong springs.
In order to show the normal state of the condenser, a scale consisting
of 15 metallic buttons to give the dimensions of the sparks, is
arranged at X. This scale is capable of being connected with the
rings, _q_ and _t_, by means of chains; when the spark obtained after 15
or 20 revolutions considerably exceeds the intervals of the scale, it
is a sure thing that the machine is in a proper state.
In order to prepare the apparatus for carriage, the winch is taken off
and placed in the compartment, _m_, which is closed by means of a
door, Q.
Figs. 5 and 6 show the arrangement of the dynamite cartridges and
wires in the blast hole. Figs. 7 to 10 show different arrangements of
the igniting wires. Figs. 11 and 12 give the general arrangement for
igniting a number of cartridges simultaneously by means of the
electric machine. Fig. 13 shows the arrangement where powder is
employed. Fig. 14 shows the arrangement of a horizontal
hole.--_Annales Industrielles._
* * * * *
IMPROVED ELECTRIC FIRE ALARM.
The object of this apparatus is to close an electric circuit when the
temperature of a room rises above a certain point. Many devices have
been invented for effecting this object, each of which have their own
advantages or disadvantages. The invention of Mr. Pritchett enables
the required result to be obtained in a very satisfactory manner. The
apparatus consists (as shown by the figure) of a long glass vessel
containing air; connected to this vessel there is a glass tube filled
with mercury. The whole is mounted on a metal cradle, which turns on
pivots. According to the position which the glass vessel and its
adjuncts occupy in the cradle (this position being adjustable by means
of a thumb-screw, seen at the upper part of the cradle), so will the
same have a tendency to rock longitudinally over to one side or the
other. Now, if we suppose the position to be such that the right hand
end of the glass vessel is depressed, and the left hand end raised,
then if the vessel becomes subjected to an elevation of temperature,
the air inside the same will become expanded, and the mercury column
in the tube will be driven over to the left, and will rise in the
turned up end of the tube. This will cause the left hand branch of the
glass vessel, and its attachments, to become increased in weight,
while the right hand branch will become proportionally lighter; the
consequence of this will be that the vessel and its cradle will cant
over, and by falling on an electrical contact will close a circuit and
sound an alarm. It is obvious that the apparatus is equally well
adapted for indicating a diminution as well as an increase of
temperature, for if the electrical contact be placed under the right
hand portion of the cradle, and the latter be adjusted so that in its
normal position its left hand portion is depressed, then when the
glass vessel becomes cooled, the air in it will contract, and the
mercury will fall in the turned-up portion of the tube before referred
to, and will rise in the limb connected to the vessel, consequently
the cradle and glass vessel will cant over in the reverse way to that
which it did in the first case.
Owing to the surface which the glass vessel exposes, the air inside
quickly responds to any external change of temperature, consequently
the apparatus is very sensitive. Another important feature is the fact
that the cradle and vessel in canting over acquires a certain
momentum, and thus the contact made becomes very certain.
[Illustration: PRITCHETT'S ELECTRIC FIRE ALARM.]
Mr. Pritchett proposes that his apparatus shall give external evidence
outside the house by ringing a gong, and by dropping a semaphore arm
released by an electromagnet. He also proposes (as has often been
suggested) that a water supply shall be automatically turned
on.--_Electrical Review._
* * * * *
A STANDARD THERMOPILE.
Dr. G. Gore, F.R.S., has invented an improved thermopile for
measuring small electromotive forces. It consists of about 300 pairs
of horizontal, slender, parallel wires of iron and German silver, the
former being covered with cotton. They are mounted on a wooden frame.
About 1½ in. of the opposite ends of the wires are bent downward to a
vertical position to enable them to dip into liquids at different
temperatures contained in long narrow troughs; the liquids being
non-conductors, such as melted paraffin for the hot junctions, and the
non-volatile petroleum, known as thin machinery oil. The electromotive
force obtained varies with the temperature; a pile of 295 pairs having
a resistance of 95.6 ohms at 16 deg. Cent. gave with a difference of
temperature of 100 deg. Cent. an electromotive force of 0.7729 volts,
or with 130 deg. Cent. an electromotive force of 1.005 volt. Each
element, therefore, equaled 0.0000262 volt for each degree Cent.
difference of temperature. On having been verified with a standard
voltaic cell the apparatus becomes itself a standard, especially for
small electromotive forces. It is capable of measuring the 1/34861
part of a volt. For higher electromotive forces than a volt, several
of these piles would have to be connected in series. The fractional
electromotive force is obtained by means of a sliding contact which
cuts out so many pairs as is required.
* * * * *
TELEPHONIC TRANSMISSION WITHOUT RECEIVERS.
The annual meeting of the French Society of Physics, the success of
which is continually increasing, took place this year in the salons of
the Observatory, which were kindly placed at the Society's disposal by
Admiral Mouchez.
There were three consecutive sessions, the one of Tuesday, April 15,
being set apart for the members of the Association, the one of the
16th for the invited guests of Admiral Mouchez, and that of the 17th
for the invited guests of the Society. The salons were partially
lighted by the Siemens differential arc, continuous current lamps, and
partially by the Swan incandescent lamp supplied by a distributing
machine that permitted of the lamps being lighted and extinguished at
will without changing the normal operation of all the rest. Many
apparatus figured at this exhibition, but we shall on the present
occasion merely call attention to those that presented a certain
character of novelty or of originality.
Among the apparatus that we shall reserve a description of for the
present was Messrs. Richard Bros.' registering thermometer designed
for the Concarneau laboratory, an instrument which, when sunk at one
mile from the coast, and to a depth of 40 meters, will give a diagram
of the temperature of the ocean at that depth; and Mr. Hospitalier's
continuous electrical indicators, designed for making known from a
distance such mechanical or physical phenomena as velocities, levels,
temperatures, pressures, etc.
Among the most important of the apparatus exhibited we must reckon Mr.
Cailletet's devices for liquefying gases, and those of Mr. Mascart for
determining the ohm. The results obtained by Mr. Mascart (which have
been submitted to the Committee on Unities of the Congress of
Electricians now in session at Paris), are sensibly concordant with
those obtained independently in England by Lord Rayleigh. Everything
leads to the hope, then, that a rapid and definite solution will be
given of this important question of electric unities, and that nothing
further will prevent the international development of the C.G.S.
system.
Mr. Jules Duboscq made a number of very successful projections, and we
particularly remarked the peculiar experiment made in conjunction with
Mr. Parinaud, that gave in projection two like spectra produced by the
same prism, and which, through superposition, were capable of
increasing the intensity of the colors, or, on the contrary, of
reconstituting white light.
Among the optical applications we may cite Mr. Leon Laurent's
apparatus for controlling plane, parallel, perpendicular, and oblique
surfaces, and magic mirrors obtained with an ordinary light; Mr. S.P.
Thompson's apparatus for demonstrating the propagation of
electro-magnetic waves in ether (according to Maxwell's theory), as
well as some new polarizing prisms; and a mode of lighting the
microscope (presented by Mr. Yvon), that was quite analogous to the
one employed more than a year ago by Dr. Van Heurck, director of the
Botanical Garden of Anvers.
Acoustics were represented by an electro-magnetic brake siren of Mr.
Bourbouze; Konig's apparatus for the synthesis of sounds; and Mr. S.P.
Thompson's cymatograph--a pendulum apparatus for demonstrating the
phenomena of beats.
It was electricity again that occupied the largest space in the
programme of the session.
Apparatus for teaching are assuming greater and greater importance
every day, and the exhibit of Mr. Ducretet included a large number of
the most interesting of these. The house of Breguet exhibited on a
reduced scale the magnificent experiments of Gaston Plante, wherein
320 leaden wire secondary elements charged for quantity with 3 Daniell
elements, and afterward coupled for tension, served to charge a
rheostatic machine formed of 50 condensers coupled for quantity. These
latter, coupled anew for tension, furnished upon being discharged a
spark due to a difference of potential of about 32,000 volts that
presented all the characters of the spark produced by induction coils
on the machines so improperly called "static." Finally, we may cite
the apparatus arranged by Mr. S.P. Thompson for studying the
development of currents in magneto-electric machines. The inventor
studies the influence of the forms of the inductors and armatures of
machines by means of an arrangement that allows him to change the
rings or armatures at will and to take out the induced bobbins in
order to sound every part of the magnetic field. Upon giving the
armature an angular motion limited by two stops, there develops a
certain quantity of electricity that may be measured by causing it to
traverse an appropriate ballistic galvanometer. Messrs. Deprez and
D'Arsonval's galvanometer answers very well for this purpose, and its
aperiodicity, which causes it quickly to return to zero as soon as the
induced current ceases, permits of a large number of readings being
taken within a very short space of time.
Measuring apparatus were represented by a new and very elegant
arrangement of Sir William Thomson's reflecting galvanometers, due to
Mr. J. Carpentier. The mounting adopted by Mr. Carpentier permits of
an easy removal of the bobbins and of an instantaneous substitution
therefor. The galvanometric part, composed of the needles and mirror,
therefore remains entirely free, thus allowing of its being verified,
and making it convenient to attach the silken fiber. Mr. Carpentier
has, moreover, adopted for all the minor apparatus a transparent
celluloid scale which simplifies them, facilitates observations, and
renders the use of reflection almost industrial.
We shall complete our enumeration of the measuring apparatus by citing
Ducretet's non-oscillating galvanometer, Sir William Thomson's
amperemeters, voltameters, ohmmeters, and mhosmeters, constructed and
exhibited by Breguet, and a new aperiodic galvanoscope of Mr. Maiche.
Mr. Baudot exhibited the recent improvements that he has made in his
multiplex printing telegraph, and M. Boudet of Paris showed a new
system of telephone transmission by submarine cables.
[Illustration: FIG. 1.--DIAGRAM EXHIBITING THE ARRANGEMENT FOR
TELEPHONIC TRANSMISSIONS WITHOUT A RECEIVER.]
Finally, we shall conclude our enumeration by referring to the
curiosities. The house of Siemens exhibited a miniature electric
railway actuated by a new model of Reynier accumulators; M. Maiche
operated a system of musical telephonic auditions that differed only
in detail from those instituted by Mr. Ader at the exhibition of 1881;
and Mr. Hospitalier presented a new form of an experiment devised by
Mr. Giltay, consisting of a telephonic transmission of sounds without
the use of receivers. Mr. Giltay's experiment is nothing but Mr.
Dunand's speaking condenser without the condenser. A glance at Fig. 1
will show how things are arranged for the experiment. The transmitting
system comprises two distinct circuits, viz.: (1) one formed of a
pile, P, of 2 or 3 Leclanche elements, or of 1 or 2 small sized
accumulators, an Ader microphane transmitter, M, and the inducting
wire of a small induction coil, B; and (2) the other formed of the
induced wire of the coil, B, of a pile, P', of 10 or 12 Leclanche
elements, and of a line whose extremities terminate at R, in two
ordinary electro-medical handles. With this arrangement the experiment
performed is as follows: When any one speaks or sings in front of the
transmitter, T, while two persons, A and B, each having one hand
gloved, are holding the handles in the ungloved hand, it is only
necessary for A to place his gloved hand upon B's ear, or for the
latter to place his hand upon A's, or for each to place his hand on
the other's ear simultaneously, in order that A or B, or A and B
simultaneously, may hear a voice issuing from the glove. Under these
circumstances, Mr. Giltay's experiment is explained like Dunand's
speaking condenser--the hand of A and the ear of B here constituting
the armature of an elementary condenser in which the glove performs
the role of dielectric.
Upon repeating this experiment at the laboratory of the School of
Physics and Industrial Chemistry of Paris, it has been found that the
glove maybe replaced by a sheet of plain or paraffined paper. In this
case, when two persons are holding the handles, and have their ears
applied, one against the other, if a sheet of paper be interposed,
airs or words will be heard to proceed therefrom. Finally, it has been
found possible to entirely suppress the paper, or dielectric, and to
hear directly, by simply interposing the auditor or auditors in the
circuit. One of the most curious forms of the experiment is the one
shown in Fig. 2. Here a third person, C, hears the hands of A and B
speak when a circuit is formed by means of three persons, A, B, and C,
the two former, A and B, each holding one of the wires of the circuit
and applying his free hand to the ear of C. Although the experiment is
one that requires entire silence, and could not on that account be
performed at the laboratory, a sort of telephonic chain can be formed
in which five or six persons may hear at the same time. A, putting his
hand on the ear of B, the latter putting his to that of C, and so on
up to the last person, who closes the circuit by grasping one of the
handles, the other one being held by A.
[Illustration: EXPERIMENT ON TELEPHONIC TRANSMISSION WITHOUT
RECEIVING APPARATUS.]
It is difficult in the present state of science to explain very
clearly how these telephonic transmissions are effected without a
receiver. All that we can conclude from it so far is that the ear is
an instrument of incomparable delicacy and of exquisite sensitiveness,
since it perceives vibrations in which the energy developer,
particularly in the telephonic chain, is exceedingly feeble.
Without any desire to seek an application for an experiment that is
simply curious, we yet believe that there is here a phenomenon of a
nature to be studied by physicists. Discoveries in telephony and
microphony have certainly opened up to science, as regards both theory
and practice, new horizons that still promise other surprises for the
future. But to return to the observatory: The success obtained by the
exhibition of the French Society of Physics shows that these reunions
respond to a genuine need--that of instructing in and popularizing
science. While warmly congratulating the organizers of these meetings,
we may express a wish that the good example set by the Society of
Physics may be followed by other societies. We are convinced in
advance that an equal success awaits them.--_La Nature._
* * * * *
ON THE ARRANGEMENT OF GROUND CONDUCTORS.
In telegraphy, as well as in the question of lightning rods, attention
has been but incidentally paid to the improvement of ground
conductors, and this point has not been the object of that careful
study that has been bestowed upon the establishment of aerial lines.
It is only recently that the interest created by lightning rods has
given rise to new forms of conductors differing from those formerly
used. The publications of the Prussian Academy of Sciences of from
1876 to 1880 contain some information of special importance in regard
to this. It is stated therein that the effect of ground conductors may
be notably increased by the division of the earth plates and the use
of metallic rods, without necessitating a greater output of material.
These facts, however, have not as yet been put to profit in practice
for the reason, perhaps, that the considerations, which have remained
general, have not at once permitted of obtaining forms what could be
employed with perfect knowledge of the results. This is what led Mr.
Ulbricht, of Dresden, to make calculations for a few forms of
conductors, and to test their approximate values. The results of these
researches are printed in the _Elektrotechnischen Zeitschrift_ for
1883 (p. 18).
[Illustration]
The equations found show, in the first place, that there exist three
means of obtaining a considerable effect, as regards the ground
conductor, with a slight expenditure of material: The cylindrical
electrode may be drawn out into the form of a bar or wire; the plate
may be rendered narrow, and elongated in the form of a ribbon; and,
besides, the annular plate may be enlarged in lessening the metallic
surface.
Finally, a short, open cylinder with a vertical axis may be formed by
curving a narrow plate or ribbon. It is not necessary to see the
formula to recognize the fact that this cylinder must behave like a
ribbon and a flat ring. The radius increasing, and the surface
remaining constant, the resistance of the earth here likewise
approaches zero.
As the resistance of the earth is inversely proportional to the
diameter of the plates, the zero resistance can also be reached by
dividing a plate _ad infinitum_. As the parts of the plate may be
brought quite close to each other without perceptibly interfering with
the action, a _network_ has finally been reached by a division carried
very far, yet limited, and by connecting the parts with one another by
conducting cylinders.
If we seek to determine what forms of ground conductors are efficient
and economical under given conditions, we shall have to begin by
informing ourselves as to the choice of material to be used for the
electrode, and shall then have to ascertain whether putting it in the
ground will or will not necessitate much outlay. The most suitable
material is copper, which may be used with advantage, in that it lasts
pretty well underground, and that the facility which it may be worked
permits of easily giving it more appropriate forms than those that can
be obtained with cast iron, which is of itself less costly.
If the burying in the ground requires little or no labor, as when
there exist ponds, rivers, and wells, or subterranean strata of water
near the surface of the earth, elongated forms of conductors will be
employed, such as the solid or hollow cylinder, the wire, the ribbon,
the narrow ring, and the network. Plates approaching a square or
circular shape are not advantageous. But if the ground has to be dug
deeply in order to sink the conductor, the form of the electrode must
be more condensed, and selected in such a way that the necessary
action may be obtained with a minimum output of copper and labor. For
great depths, and when the ground will permit of boring, an elongated
and narrow cylinder will be used. Such a system, however, can only be
employed when the cylinder is surrounded by spring water, since,
without that, an intimate contact with earth that is only moist,
cannot be obtained with certainty. In earth that is only moist and for
moderate depths, preference may be given to an electrode laid down
flat. The digging necessary in this case is onerous, it is true, but
it permits of very accurately determining the state of the earth
beneath and of obtaining a very perfect adherence of the electrode
therewith. Two forms, the annular ribbon or the flat ring and the
network, present themselves, according to calculations, as a
substitute for copper plates, which are so expensive; and these forms
are satisfactory on condition that the labor of digging be not notably
increased. These forms should always have a diameter a little greater
than that of the plate. The flat ring and the network, however, offer
one weak point, which they possess in common with the plate, and that
is, their dimensions cannot be easily adapted to the nature of the
ground met with without a notable increase in the expense. Now, if the
ground should offer a conductivity less than what was anticipated, and
it were desired to increase the plate, say by one-third, it would be
impossible to do so as a consequence of the closed form.
One important advantage is realized in this respect by combining the
ring and the network in the form of a reticulated ring having a
diameter of from 1 to 1½ meters. On cutting this ring at a given place
and according to a certain radius we obtain the reticulated ribbon
shown in the accompanying figure. The thickness of the wires is 2.5
mm., and their weight is 0.475 kilo. per meter. L, L, and L are the
points at which the conducting cable is soldered. A reticulated ribbon
of copper can be made in advance of any length whatever, and,
according to local exigencies, it may be easily curved and given the
form of a flat or cylindrical ring of varying width. Even though the
ribbon has already been cut for a ring of given diameter, it may be
still further enlarged by drawing it out and leaving a bit of the ring
open, so as to thus obtain a nearly corresponding diminution in the
resistance. Such a resistance may be still further diminished by
rendering the ring higher, that is to say, by employing an annular
cylindrical form.
After assuring himself, by experiments on a small scale, that
calculation and observation gave concordant results for the flat ring,
the author made an experiment on a larger scale with the annular
network. For practical reasons he employed for this purpose a copper
wire 2.5 mm. in diameter, which may be expected to last as long as one
of iron plate 2 mm. in thickness. Calculation showed that in a ribbon
160 mm. wide, meshes 40 mm. in breadth were advantageous and favorable
as regards rigidity. A reticulated ribbon like this, 4 meters in
length, was made and formed into a flat ring having an external
diameter of 1.42 m. and an internal one of 1.10 m. The resistance of
this ring was found to be W = 0.3485 (1/_k_), and that of a plate one
meter square, W0 = 0.368 (1/_k_).
As the conductivity of the earth is very variable, and as we cannot
have an absolute guarantee that the ramming will be uniform, it seemed
proper to make the measurements of the resistance by fixing the plate
and the ring in succession to the lower surface of a small raft, in
such a way that the contact with the water should correspond as well
as possible to the suppositions made for the calculation. As a second
ground conductor, a system of water pipes was used, and, after this, a
lightning rod conductor, etc.
Repeated and varied experiments gave, for the calculation of the
values of the resistances, equations so concordant that the following
results may be considered very approximate.
The square plate had a resistance of 35.5 Siemens units, and the
reticulated ring one of 32.5. From the first figure we deduce k =
1/91.12, that is to say, the specific conductivity of river-water is
1:91120000. Calculation, then, gives as the resistance of the earth in
Siemens units:
Calculated. Observed.
Square plate. 33.5 33.5
Annular ring. 31.76 32.5
These figures prove the accuracy of the calculations that had been
made in an approximate way.
The experiments were performed upon the Elba, above Dresden. Other
experiments still had reference to the influence of immersion. In
order to diminish polarization, only instantaneous currents from the
measuring pile were employed. It was to be supposed that the current
of water through which the bubbles of gas were removed from the
electrodes would not have permitted of a notable resistance of
polarization. Later measurements, made upon a ribbon buried, like the
plates, in the earth, gave likewise most favorable results.
As a result of these experiments, the State railways of Saxony have,
in such cases as were practicable, introduced the annular network of
copper. There are some manufacturers, too, who seem desirous of
adopting this system, although it has hardly emerged from the period
of experiment. The pecuniary advantages that will result from an
application of it ought, it would seem, to dispel a large proportion
of the criticisms directed against the erection of lightning rods,
from the standpoint of expense, and contribute to extend an
arrangement which may be considered as a very happy one.
If we compare the square plate with the equivalent annular network,
constructed as above indicated, and which should possess, according to
the author an external diameter of 1.26 m. and of 3.45 m., we find
that:
The square plate, 1 mm. thick weighs 8.9 kilos.
" 2 " " " 17.8 "
The annular network " 1.64 "
The cost of reticulated ribbon per meter amounts to about 4.4 francs,
supposing it to be arranged as shown in the cut.
As term of comparison, we may admit that the following forms are
nearly the equivalent of a horizontal, unburied plate one meter
square.
Length. Diameter.
Vertical cylinder buried 1.40 m. 0.13 m.
" " " 1.80 m. 0.06 m.
Vertical bar " 2.60 m. 0.013 m.
Horizontal bar " 5.20 m. 0.013 m.
Horizontal flat ring 1.32 m. in external diameter, and 1.08 m.
internal.
Horizontal network 1.01 m. square, and having meshes of the same size
as those of the reticulated ribbon.
Horizontal reticulated ribbon 3 m. in length and of the structure
described.
Horizontal annular ring 1.26 m. in external diameter, 0.94 m.
internal.
In conclusion, let us meet an objection that might be made to the
accuracy of the hypotheses that serve as a base to the preceding
calculations, in cases where ground plates for lightning rods and not
for telegraphs are concerned. Between the two ground plates of a
telegraph line there is generally a distance such that the curves of
the current undergo no deviation in the vicinity of one of the
electrodes (the only part important for integrations) through the
influence of the other. But it might be admitted that such would prove
the case with a lightning rod in a storm, at the time of the passage
of the fluid into the earth. The ground plate here is one of the
electrodes, and the other is replaced by the surface of the earth
strongly charged to a great distance under the storm clouds. If we
suppose (what may be admitted in a good lightning rod) that there no
longer occurs any spark from the point downward, the curves of the
current, in starting perpendicularly from the ground plate, would be
obliged to leave their rectilinear trajectory and strike the surface
of the earth at right angles. When the electricity flows through a
plane surface into an infinite body, it is only when such surface
presents a very great development that the respective potentials
decrease very slowly in the vicinity of the said surface. No notable
modification occurs, then, in the curves of equal potential, in the
vicinity of the ground plate through the action of this extended
charge, nor consequently any modification in the curves of the
current; but the electricity which spreads has but a short distance to
travel in order to overcome the most important resistances.
The calculations of resistances given above have, then, the same value
for discharges of atmospheric electricity.--_Bull. du Musee de
l'Industrie._
* * * * *
ON ELECTROLYSIS.
By H. SCHUCHT.
Concerning the separations which take place at the positive pole, the
composition of the peroxides, and the manner of their determination,
relatively little has been done.
If solutions of the salts of lead, thallium, silver, bismuth, nickel,
and cobalt are decomposed by the current between platinum electrodes,
metal is deposited at the negative, and oxide at the positive
electrode. Manganese is precipitated only as peroxide. The formation
of peroxide is, of course, effected by the ozone found in the
electrolytic oxygen at the positive pole; the oxide existing in
solution is brought to a higher degree of oxidation, and is separated
out. Its formation may be decreased or entirely prevented by the
addition of readily oxidizible bodies, such as organic acids, lactose,
glycerine, and preferably by an excess of oxalic acid; but only until
the organic matter is transformed into carbonic acid. In this manner
Classen separates other metals from manganese in order to prevent the
saline solutions from being retained by the peroxide.
With solutions of silver, bismuth, nickel, and cobalt, it is often
practicable to prevent the separation of oxide by giving the current a
greater resistance--increasing the distance between the electrodes.
The proportion between the quantities of metal and of peroxide
deposited is not constant, and even if we disregard the concentration
of the solution, the strength of the current and secondary influences
(action of nascent hydrogen) is different in acid and in alkaline
solutions. In acid solutions much peroxide is formed; in alkaline
liquids, little or none. The reason of the difference is that ozone is
evolved principally in acid solutions, but appears in small quantities
only in alkaline liquids, or under certain circumstances not at all.
The quantity of peroxide deposited depends also on the temperature of
the saline solution; at ordinary temperatures the author obtained more
peroxide--the solution, the time, and the strength of current being
equal--than from a heated liquid. The cause is that ozone is destroyed
by heat and converted into ordinary oxygen. With the exception of lead
and thallium the quantity of metal deposited from an acid solution is
always greater than that of the peroxide.
_Lead._--Luckow has shown that from acid solutions--no matter what may
be the acid--lead is deposited at the anode as a mixture of anhydrous
and hydrated peroxide of variable composition. Only very strongly acid
solutions let all their lead fall down as peroxide; the precipitation
is rapid immediately on closing the circuit, and complete separation
is effected only in presence of at least 10 per cent. of free nitric
acid. As the current becomes stronger with the increase of free acid,
there is deposited upon the first compact layer a new stratum of
loosely adhering peroxide.
In presence of small quantities of other metals which are thrown down
by the current in the metallic state, such as copper, mercury, etc.,
peroxide alone is deposited from a solution of lead containing small
quantities only of free nitric acid.
The lead peroxide deposited is at first light brown or dark red, and
becomes constantly darker and finally taking a velvet-black. As its
stratification upon the platinum is unequal, it forms beautifully
colored rings.
Experiments show that the quantity of peroxide deposited depends on
the nature of the solution and the strength of the current. In case of
very feeble currents and slight acidity, its quantity is so small that
it does not need to be taken into consideration. If the lead solution
is very dilute scarcely any current is observed, lead solutions _per
se_ being very bad conductors of electricity.
Faintly acid concentrated lead solutions give loose peroxide along
with much spongy metallic lead. Free alkali decreases the separation
of peroxide; feebly alkaline solutions, concentrated and dilute, yield
relatively much peroxide along with metallic lead, while strongly
alkaline solutions deposit no peroxide.
Dried lead peroxide is so sparingly hygroscopic that it may be weighed
as such; its weight remains constant upon the balance for a long time.
In order to apply the peroxide for quantitative determinations, a
large surface must be exposed to action. As positive electrode a
platinum capsule is convenient, and a platinum disk as negative pole.
The capsule shape is necessary because the peroxide when deposited in
large quantities adheres only partially, and falls in part in thin
loose scales. It is necessary to siphon off the nitric solution,
since, like all peroxides, that of lead is not absolutely insoluble in
nitric acid. The methods of Riche and May give results which are
always too high, since portions of saline solution are retained by the
spongy deposit and can be but very imperfectly removed by washing.
This is especially the case in presence of free alkali.
The author has proceeded as follows: The lead peroxide is dried in the
capsule, and there is passed over it pure dry gaseous sulphurous acid
in a strong current from a rather narrow delivery tube. Lead sulphate
is formed with evolution of heat; it is let cool under the exsiccator,
and weighed as such. Or he ignites the peroxide along with finely
pulverized ammonium sulphite; the mass must have a pure white color.
After the conclusion of the reaction it is ignited for about 20
minutes. The results are too high. The proportion of actual lead
peroxide in the deposit ranges from 94 to 94.76 per cent. The peroxide
precipitated from a nitric solution may, under certain circumstances,
be anhydrous. This result is due to the secondary influences at the
positive pole, where the free acid gradually withdraws water from the
peroxide.
The peroxide thrown down from alkaline solutions retains alkali so
obstinately that it cannot be removed by washing; the peroxide plays
here the part of an acid. The lead nitrate mechanically inclosed in
the peroxide is resolved by ignition into oxide, hyponitric acid, and
oxygen; this small proportion of lead oxide does not exert an
important influence on the final result. The quantity of matter
mechanically inclosed is relatively high, as in the precipitation of
much lead peroxide there is relatively more saline matter occluded
than when a few centigrammes are deposited. The peroxide incloses also
more foreign matter if it is thrown down upon a small surface than if
it is deposited in a thin layer over a broad surface. From numerous
analyses the author concludes that in presence of much free nitric
acid the proportion of water is increased; with free alkali the
reverse holds good.
_Thallium_ behaves similarly to lead. From a nitric acid solution it
is thrown down, according to the proportion of free acid, either as
sesquioxide only or in small quantities as silvery, metallic leaflets;
from alkaline solutions it is deposited as sesquioxide and metal, the
latter of a lead-gray color. Thallium solutions conduct the electric
current badly. Thallium oxide resembles lead peroxide in color; at a
strong heat it melts, becomes darker, and is converted into peroxide,
in which state it can be weighed.
_Silver._--All solutions of silver salts, except the nitrate, and
those containing a very large quantity of free nitric acid or
nitrates, deposit electrolytically merely metallic silver. In the
above mentioned exceptional cases there is formed a small quantity of
peroxide which adheres to the anode as a blackish-gray deposit. The
greatest quantity of peroxide is obtained on employing a concentrated,
strongly acid solution of the nitrate, and a strong current. If the
solution is very dilute we obtain no peroxide, or mere traces which
disappear again toward the end of the process. The peroxide is
deposited at first in small, dark, shining octahedral crystals;
subsequently, in an amorphous state. At 110° it evolves oxygen
suddenly, and is converted into metallic silver. It dissolves in
ammonia with a violent escape of nitrogen. In nitric acid it dissolves
without decomposition and with a red color.
The author uses a galvanic current for reducing silver residues,
consisting of sulphocyanide. The salt is mixed with sulphuric acid in
a roomy platinum capsule, and a fine platinum wire gauze is used as
positive electrode.
_Bismuth._--The current resolves bismuth solutions into metal and
bismutic acid. The latter is deposited at the positive pole, and in
thin layers appears of a golden-yellow, but in thick strata is darker,
approaching to red. Its formation is very gradual, and in time it
disappears again, owing to secondary actions of the current. On
ignition it becomes lemon yellow, and transitorily darker, even brown,
and passes into the sexquioxide.
_Nickel and Cobalt._--On the electrolysis of the ammonical solution
the sesquioxide appears at the positive pole. Its formation is
prevented by an excess of ammonia. The author never obtains more than
3½ per cent. of the quantity of the metal. The sesquioxides dissolve
in ammonia without escape of nitrogen, and are usually anhydrous.
_Manganese._--Manganese is the only metal which is precipitated only
as peroxide. It is deposited at once on closing the circuit, and is at
first brown, then black and shining. Organic acids, ferrous oxide,
chromic oxide, ammonium salts, etc., prevent the formation of peroxide
and the red color produced by permanganic acid. In very dilute
strongly acid nitric solutions there is formed only permanganic acid,
which according to Riche is plainly visible in solutions containing
1/1000000 grm. manganese. On electrolyzing a manganiferous solution of
copper nitrate, red permanganic acid appeared in a stratum floating
above the platinum disk coated with brown peroxide. No manganese
peroxide was deposited. The peroxide adheres firmly to the platinum
when the proportion of free acid is small, not exceeding 3 per cent.,
and the current is not too strong. If the action of the current is
prolonged after the peroxide is thrown down, it falls off in laminæ.
According to Riche, in a nitric solution the manganese is deposited as
peroxide, also at the negative pole. This formation is not directly
due to the current, but is a precipitate occasioned by the production
of ammonia by the reduction of nitric acid. To determine the manganese
in peroxide electrolytically precipitated, it is heated to bright
redness in the platinum capsule until the weight becomes constant. The
results are too high.
_Selenium and Tellurium._--Both these bodies are readily and
completely reduced by the current either in acid or alkaline
solutions. Selenium is thrown down at first of a fine brownish red,
which gradually becomes darker. The deposit of tellurium is of a
bluish black color. If the current is feeble, the deposit of selenium
is moderately compact; that of tellurium is always loose, and it often
floats on the liquid. A strong current precipitates both as powders.
The positive pole is coated during electrolysis with a film of a dark
color in case of selenium, but of a lemon yellow with tellurium. As in
case of arsenic and antimony, the hydrogen evolved at the negative
pole combines with the reduced substances, forming hydrogen, selenide,
or telluride, which remain in part in solution in the liquid. The
reduced metal separates out at the anode in a friable
condition.--_Zeitschrift fur Analytische Chemie, and Chemical News._
* * * * *
THE ELECTRO-CHEMICAL EQUIVALENT OF SILVER.
A very careful and important determination of the electrochemical
equivalent of silver has been made at the observatory of the Physical
Institute of Würzbourg, and the results are that an ampere current
flowing for a second, or a coulomb of electricity deposits 1.1183
milligrammes of silver or 0.3281 milligramme of copper, and decomposes
0.09328 milligramme of water, a result agreeing closely with that of
Lord Rayleigh recently communicated to the Physical Society. An ampere
therefore deposits 4.0259 grammes of silver per hour; Kohlrausch's
value is 4.0824, a value hitherto accepted universally. This value is
so useful in measuring electric currents with accuracy, and free from
the disturbances of magnetism, etc., that it is eminently satisfactory
to find the German value agree with that of Lord Rayleigh, which will
probably be adopted by English electricians.
* * * * *
A NEW STANDARD LIGHT.
Herr Hefner-Alteneck has suggested a new standard light for
photometric purposes, which promises to be very simple and effective
in operation. The light is produced by an open flame of amyl-acetate
burning from a wick of cotton fiber which fills a tube of German
silver 1 in. long and 316 mils. internal diameter; the external
diameter being 324 mils. The flame is 1.58 in. high from top to
bottom; and it should be lighted at least ten minutes before using the
light for testing. A cylindrical glass chimney surrounds it to ward
off air currents. About 2 per cent. of the light is absorbed by the
glass. The power of the flame is that of a standard English candle;
and experiments have shown that amyl acetate, which besides is not
expensive, is the best fuel for steadiness and brilliance. Neither the
substitution of commercial amyl-acetate for pure nor the use of a wick
of cotton thread for loose cotton fiber alters the illuminating power;
but the wick should be trimmed square across the mouth of the tube,
for if it project and droop the illuminating power is increased.
* * * * *
[NATURE.]
DR. FEUSSNER'S NEW POLARIZING PRISM.
In a recent number of the _Zeitschrift fur Instrumentenkunde_ (iv.,
42-50, February, 1884), Dr. K. Feussner of Karlsruhe has given a
detailed description of a polarizing prism lately devised by him,
which presents several points of novelty, and for which certain
advantages are claimed. The paper also contains an account, although
not an exhaustive one, of the various polarizing prisms which have
from time to time been constructed by means of different combinations
of Iceland spar. The literature of this subject is scattered and
somewhat difficult of access, and moreover only a small part of it has
hitherto been translated into English; and it would appear therefore
that a brief abstract of the paper may not be without service to those
among the readers of _Nature_ who may be unacquainted with the
original memoirs, or who may not have the necessary references at
hand.
Following the order adopted by Dr. Feussner, the subject may be
divided into two parts:
I.--OLDER FORMS OF POLARIZING PRISMS.
In comparing the various forms of polarizing prisms, the main points
which need attention are--the angular extent of the field of view, the
direction of the emergent polarized ray, whether it is shifted to one
side of, or remains symmetrical to the long axis of the prism; the
proportion which the length of the prism bears to its breadth; and
lastly, the position of the terminal faces, whether perpendicular or
inclined to the long axis. These requirements are fulfilled in
different degrees by the following methods of construction:
[Illustration: Fig. 1., Fig. 2., and Fig. 3.]
1. _The Nicol Prism_ (_Edin. New Phil. Journal_, 1828, vi., 83).--This
(Fig. 1), as is well known, is constructed from a rhombohedron of
Iceland spar, the length of which must be fully three times as great
as the width. The end faces are cut off in such a manner that the
angle of 72° which they originally form with the lateral edge of the
rhombohedron is reduced to 68°. The prism is then cut in two in a
plane perpendicular to the new end surfaces, the section being carried
obliquely from one obtuse corner of the prism to the other, in the
direction of its length. The surfaces of this section, after having
been carefully polished, are cemented together again by means of
Canada balsam. A ray of light, on entering the prism, is separated by
the double refraction of the calc-spar into an ordinary and an
extraordinary ray; the former undergoes total reflection at the layer
of balsam at an incidence which allows the extraordinary ray to be
transmitted; the latter, therefore, passes through unchanged. This
principle of obtaining a single polarized ray by means of total
reflection of the other is common to all the forms of prism now to be
described.
Dr. Feussner gives a mathematical analysis of the paths taken by the
two polarized rays within the Nicol prism, and finds that the emergent
extraordinary ray can include an angular field of 29°, but that this
extreme value holds good only for rays incident upon that portion of
the end surface which is near to the obtuse corner, and that from
thence it gradually decreases until the field includes an angle of
only about half the previous amount. He finds, moreover, that,
although of course the ray emerges parallel to its direction of
incidence, yet that the zone of polarized light is shifted to one side
of the central line. Also that the great length of the Nicol--3.28
times its breadth--is not only an inconvenience, but owing to the
large pieces of spar thus required for its construction, prisms of any
but small size become very expensive. To this it may be added that
there is a considerable loss of light by reflection from the first
surface, owing to its inclined position in regard to the long axis of
the prism.
[Illustration: Fig. 4., Fig. 5., and Fig. 6.]
It is with the view of obviating these defects that the modifications
represented in Figs. 2 to 6 have been devised.
2. _The Shortened Nicol Prism_.--This arrangement of the Nicol prism
is constructed by Dr. Steeg and Reuter of Homburg v.d.H. For the sake
of facility of manufacture, the end surfaces are cleavage planes, and
the oblique cut, instead of being perpendicular, makes with these an
angle of about 84°. By this alteration the prism becomes shorter, and
is now only 2.83 times its breadth; but if Canada balsam is still used
as the cement, the field will occupy a very unsymmetrical position in
regard to the long axis. If balsam of copaiba is made use of, the
index of refraction of which is 1.50, a symmetrical field of about 24°
will be obtained. A prism of this kind has also been designed by Prof.
B. Hasert of Eisenach (_Pogg. Ann._, cxiii., 189), but its performance
appears to be inferior to the above.
3. _The Nicol Prism with Perpendicular Ends._--The terminal surfaces
in this prism are perpendicular to the long axis, and the sectional
cut makes with them an angle of about 75°. The length of the prism is
3.75 times its breadth, and if the cement has an index of refraction
of 1.525, the field is symmetrically disposed, and includes an angle
of 27°. Prisms of this kind have been manufactured by Dr. Steeg, Mr.
C.D. Ahrens, and others.
4. _The Foucault Prism_ (_Comptes Rendus_, 1857, xlv., 238).--This
construction differs from all those hitherto mentioned, in that a film
of air is employed between the two cut surfaces as the totally
reflecting medium instead of a layer of cement. The two halves of the
prism are kept in position, without touching each other, by means of
the mounting. The length of the prism is in this way much reduced, and
amounts to only 1.528 times its breadth. The end surfaces are cleavage
planes, and the sectional cut makes with them an angle of 59°. The
field, however, includes not more than about 8°, so that this prism
can be used only in the case of nearly parallel rays; and in addition
to this the pictures which may be seen through it are to some extent
veiled and indistinct, owing to repeated internal reflection.
5. _The Hartnack Prism_ (_Ann. de Ch. et de Physique_, ser. iv., vii.,
181).--This form of prism was devised in 1866 by MM. Hartnack and
Prazmowiski; the original memoir is a valuable one; a translation of
it, with some additions, has lately been published (_Journ. of the R.
Microscopical Soc._, June, 1883, 428). It is considered by Dr.
Feussner to be the most perfect prism capable of being prepared from
calc-spar. The ends of the prism are perpendicular to its length; the
section carried through it is in a plane perpendicular to the
principal axis of the crystal. The cementing medium is linseed oil,
the index of refraction of which is 1.485. This form of prism is
certainly not so well known in this country as it deserves to be; a
very excellent one, supplied to the present writer by Dr. Steeg is of
rectangular form throughout, the terminal surfaces are 19 × 15 mm.,
and the length 41 mm. The lateral shifting of the field is scarcely
perceptible, the prism is perfectly colorless and transparent, and its
performance is far superior to that of the ordinary Nicol. The field
of view afforded by this construction depends upon the cementing
substance used, and also upon the inclination of the sectional cut in
regard to the end of the prism; it may vary from 20° to 41°. If the
utmost extent of field is not required, the prism may be shortened by
lessening the angle of the section, at the expense, however, of
interfering with the symmetrical disposition of the field.
6. _The Glan Prism_ (Carl's "Repertorium," xvi., 570, and xvii.,
195).--This is a modification of the Foucault, and in a similar manner
includes a film of air between the sectional surfaces. The end
surfaces and also the cut carried through the prism are parallel to
the principal axis of the calc-spar. The ends are normal to the
length, and the field includes about 8°. This prism is very short, and
may indeed be even shorter than it is broad. It is subject to the same
defect as that mentioned in the case of the Foucault, although perhaps
not quite to the same extent.
II.--THE NEW POLARIZING PRISM.
This prism differs very considerably from the preceding forms, and
consists of a thin plate of a doubly refracting crystal cemented
between two wedge-shaped pieces of glass, the terminal faces of which
are normal to the length. The external form of the prism may thus be
similar to the Hartnack, the calc-spar being replaced by glass. The
indices of refraction of the glass and of the cementing medium should
correspond with the greater index of refraction of the crystal, and
the directions of greatest and least elasticity in the latter must
stand in a plane perpendicular to the direction of the section. One of
the advantages claimed for the new prism is that, it dispenses with
the large and valuable pieces of spar hitherto found necessary; a
further advantage being that other crystalline substances may be used
in this prism instead of calc-spar. The latter advantage, however,
occurs only when the difference between the indices of refraction for
the ordinary and extraordinary rays in the particular crystal made use
of is greater than in calc-spar. When this is the case, the field
becomes enlarged, and the length of the prism is reduced.
[Illustration: Fig. 7.]
The substance which Dr. Feussner has employed as being most suitable
for the separating crystal plate is nitrate of soda (_natronsalpeter_),
in which the above-mentioned values are [omega] = 1.587 and [eta] =
1.336. It crystallizes in similar form to calcite, and in both cases
thin plates obtained by cleavage may be used.
As the cementing substance for the nitrate of soda, a mixture of gum
dammar with monobromonaphthalene was used, which afforded an index of
refraction of 1.58. In the case of thin plates of calcite, a solid
cementing substance of sufficiently high refractive power was not
available, and a fluid medium was therefore employed. For this purpose
the whole prism was inclosed in a short glass tube with airtight ends,
which was filled with monobromonaphthalene. In an experimental prism a
mixture of balsam of tolu was made use of, giving a cement with an
index of refraction of 1.62, but the low refractive power resulted in
a very considerable reduction of the field. The extent and disposition
of the field may be varied by altering the inclination at which the
crystal lamina is inserted (Fig. 7), and thereby reducing the length
of the prism, as in the case of the Hartnack.
In order to obviate the effects of reflection from the internal side
surfaces if the prism, the wedge-shaped blocks of glass of which it is
built up may be made much broader than would otherwise be necessary;
the edges of this extra width are cut obliquely and suitably
blackened.
The accompanying diagram (Fig. 8) represents a prism of cylindrical
external form constructed in this manner, the lower surface being that
of the incident light. In this the field amounts to 30°, and the
breadth is about double the length.
[Illustration: Fig. 8.]
Dr. Feussner remarks that a prism similar in some respects to his new
arrangement was devised in 1869 by M. Jamin (_Comptes Rendus_,
lxviii., 221), who used a thin plate of calc-spar inclosed in a cell
filled with bisulphide of carbon; and also by Dr. Zenker, who replaced
the liquid in M. Jamin's construction by wedges of flint glass.
Among others, the carefully considered modifications of the Nicol
prism which have recently been devised by Prof. S.P. Thompson (_Phil.
Mag._, November, 1881, 349, and _Jour. R. Micros. Soc._, August, 1883,
575), and by Mr. R.T. Glazebrook (_Phil. Mag._, May, 1883, 352), do
not appear to have been known to Dr. Feussner.
The following tabular view of different forms of polarizing prisms is
taken from the conclusion of Dr. Feussner's paper:
---------------------------------------+------+---------+------+------
| |Inclina- |Ratio |
| |tion of | of |
| |section |length|
| |in regard| to |
| |to long |clear |
|Field.|axis. |width.|Fig.
---------------------------------------+------+---------+------+------
I. THE OLD POLARISING PRISMS. | ° | ° | |
1. Nicol's prism. | 29 | 22 | 3.28 | 1
2. Shortened Nicol prism-- | | | |
a. Cemented with Canada balsam.| 13 | 25 | 2.83 | 2
b. Cemented with copaiba " | 24 | 25 | 2.83 | 2
3. Nicol with perpendicular ends-- | | | |
a. With Canada balsam. | 20 | 15 | 3.73 | 3
b. With cement of index of | | | |
refraction of 1.525. | 27 | 15 | 3.73 | 3
4. Foucault's prism. | 8 | 40 | 1.528| 4
5. Hartnack's prism-- | | | |
a. Original form. | 35 | 15.9 | 3.51 |5 _a b_
b. With largest field. | 41.9 | 13.9 | 4.04 |5 _a a_
c. With field of 30°. | 30 | 17.4 | 3.19 |5 _a c_
d. With field of 20°. | 20 | 20.3 | 2.70 |5 _a d_
6. Glan's prism. | 7.9 | 50.3 | 0.831| 6
| | | |
II. THE NEW POLARISING PRISM. | | | |
1. With calc-spar: largest field. | 44 | 13.2 | 4.26 |5 _a a_
2. " field of 30°. | 30 | 17.4 | 3.19 |5 _a c_
3. " field of 20°. | 20 | 20.3 | 2.70 |5 _a d_
4. With nitrate of soda: | | | |
" largest field. | 54 | 16.7 | 3.53 |7 _a a_
5. " field of 30°. | 30 | 24 | 2.25 |7 _a b_
6. " field of 20°. | 20 | 27 | 1.96 |7 _a c_
---------------------------------------+------+---------+------+------
As an analyzing prism of about 6 mm. clear width, and 13.5 mm. long,
the new prism is stated by its inventor to be of the most essential
service, and it would certainly appear that the arrangement is rather
better adapted for small prisms than for those of considerable size.
Any means by which a beam of polarized light of large diameter--say 3
to 3½ inches--could be obtained with all the convenience of a Nicol
would be a real advance, for spar of sufficient size and purity for
such a purpose has become so scarce and therefore so valuable that
large prisms are difficult to procure at all. So far as an analyzer is
concerned, the experience of the writer of this notice would lead to
the opinion that improvements are to be looked for rather in the way
of the discovery of an artificial crystal which absorbs one of the
polarized rays than by further modifications depending upon total
reflection. The researches of Dr. Herapath on iodosulphate of quinine
(_Phil. Mag._, March, 1852, 161, and November, 1853, 346) are in this
direction; but crystals of the so-called herapathite require great
manipulative skill for their production. If these could be readily
obtained of sufficient size, they would be invaluable as analyzers.
This opinion is supported by the existence of an inconvenience which
attends every form of analyzing prism. It is frequently, and
especially in projecting apparatus, required to be placed at the focus
of a system of lenses, so that the rays may cross in the interior of
the prism. This is an unfavorable position for a prismatic analyzer,
and in the case of a powerful beam of light, such as that from the
electric arc, the crossing of the rays within the prism is not
unattended with danger to the cementing substance, and to the surfaces
in contact with it.
PHILIP R. SLEEMAN.
* * * * *
ZIRCON.
By F. STOLBA.
Finely ground zircon is quickly rendered soluble if fused with a
mixture of potassium borofluoride and potassium carbonate. The author
takes two parts of the former to three of the latter, and prepares an
intimate, finely divided mixture, which is kept ready for use.
Of this mixture four parts are taken to one of zircon, thoroughly
mixed, and melted in a platinum crucible at a red heat. The mass fuses
readily, froths at first and gives off bubbles of gas, and flows then
quietly, forming a very fluid melt. If the zircon is finely ground, 15
minutes are sufficient for this operation. The loss of weight is 16
per cent., and is not notably increased on prolonged fusion. It
corresponds approximately to the weight of the carbonic anhydride
present in the potassium carbonate.
As pungent vapors are given off during fusion, the operation should be
conducted under a draught hood. The activity of the mixture in
attacking zircon appears from the following experiment: Two zircon
crystals, each weighing ½ grm., were introduced into the melted
mixture and subjected to prolonged heat. In a short time they
decreased perceptibly in size; each of them broke up into two
fragments, and within an hour they were entirely dissolved. The melted
mass is poured upon a dry metal plate, and when congealed is thrown
into water. It is at once intersected with a number of fissures, which
facilitate pulverization. This process is the more necessary as the
unbroken mass is very slowly attacked by water even on prolonged
boiling. The powder is boiled in a large quantity of water so as to
remove everything soluble. There is obtained a faintly alkaline
solution and a sediment insoluble in water. From the filtrate alkalies
throw down zirconium hydroxide, free from iron.
The portion insoluble in water is readily dissolved in hydrofluoric
acid, and is converted into zircon potassium fluoride. The chief bulk
of the zirconium is found in the aqueous solution in the state of
double fluorides. The platinum crucible is not in the least attacked
during melting. On the contrary, dirty platinum crucibles may be
advantageously cleaned by melting in them a little of the above
mentioned mixture.
If finely divided zircon is boiled for a long time with caustic lye,
it is perceptibly attacked. It is very probable that in this manner
zircon might be entirely dissolved under a pressure of 10 atmospheres.
Potassium borofluoride may be readily prepared from cryolite.
Crucibles of nickel seem especially well adapted for the fusion of
zircon in caustic alkalies.--_Ber. Boehm. Gesell. Wissenschaft;
Chem. News_.
* * * * *
A PROCESS FOR MAKING WROUGHT IRON DIRECT FROM THE ORE.[1]
[Footnote 1: A paper read at the Cincinnati Meeting of the
American Institute of Mining Engineers, by Willard P. Ward, A.M.,
M.E., February, 1884.]
The numerous direct processes which have been patented and brought
before the iron masters of the world, differ materially from that now
introduced by Mr. Wilson. After a careful examination of his process,
I am convinced that Mr. Wilson has succeeded in producing good blooms
from iron ore, and I think that I am able to point out theoretically
the chief reasons of the success of his method.
Without going deeply into the history of the metal, I may mention the
well known fact that wrought iron was extensively used in almost all
quarters of the globe, before pig or cast iron was ever produced.
Without entering into the details of the processes by which this
wrought iron was made, it suffices for my present purpose to say that
they were crude, wasteful, and expensive, so that they can be employed
to-day only in a very few localities favored with good and cheap ore,
fuel, and labor.
The construction of larger furnaces and the employment of higher
temperatures led to the production of a highly carbonized, fusible
metal, without any special design on the part of the manufacturers in
producing it. This pig iron, however, could be used only for a few
purposes for which metallic iron was needed; but it was produced
cheaply and with little loss of metal, and the attempt to decarbonize
this product and bring it into a state in which it could be hammered
and welded was soon successfully made. This process of decarbonization,
or some modification of it, has successfully held the field against
all so-called, direct processes up to the present time. Why? Because
the old fashioned bloomeries and Catalan forges could produce blooms
only at a high cost, and because the new processes introduced failed
to turn out good blooms. Those produced were invariably "red short,"
that is, they contained unreduced oxide of iron, which prevented the
contact of the metallic particles, and rendered the welding together
of these particles to form a solid bloom impossible.
The process of puddling cast iron, and transforming it by
decarbonization into wrought iron, has, as everybody knows, been in
successful practical operation for many years, and the direct process
referred to so closely resembles this, that a short description of the
theory of puddling is not out of place here.
The material operated on in puddling is iron containing from 2½ to 4
per cent. of carbon. During the first stage of the process this iron
is melted down to a fluid bath in the bottom of a reverberatory
furnace. Then the oxidation of the carbon contained in the iron
commences, and at the same time a fluid, basic cinder, or slag, is
produced, which covers a portion of the surface of the metal bath, and
prevents too hasty oxidation. This slag results from the union of
oxides of iron with the sand adhering to the pigs, and the silica
resulting from the oxidation of the silicon contained in the iron.
This cinder now plays a very important part in the process. It takes
up the oxides of iron formed by the contact of the oxidizing flame
with the exposed portion of the metal bath, and at the same time the
carbon of the iron, coming in contact with the under surface of the
cinder covering, where it is protected from oxidizing influences,
reduces these oxides from the cinder and restores them to the bath in
metallic form. This alternate oxidation of exposed metal, and its
reduction by the carbon of the cast iron, continues till the carbon is
nearly exhausted, when the iron assumes a pasty condition, or "comes
to nature," as the puddlers call this change. The charge is then
worked up into balls, and removed for treatment in the squeezer, and
then hammered or rolled. In the Wilson process the conditions which we
have noted in the puddling operation are very closely approximated.
Iron ore reduced to a coarse sand is mixed with the proper proportion
of charcoal or coke dust, and the mixture fed into upright retorts
placed in the chimney of the puddling furnace. By exposure for 24
hours to the heat of the waste gases from the furnace, in the presence
of solid carbon, a considerable portion of the oxygen of the ore is
removed, but little or no metallic iron is formed. The ore is then
drawn from the deoxidizer into the rear or second hearth of the
puddling furnace, situated below it, where it is exposed for 20
minutes to a much higher temperature than that of the deoxidizer. Here
the presence of the solid carbon, mixed with the ore, prevents any
oxidizing action, and the temperature of the mass is raised to a point
at which the cinder begins to form. Then the charge is carried forward
by the workmen to the front hearth, in which the temperature of a
puddling furnace prevails. Here the cinder melts, and at the same
time the solid carbon reacts on the oxygen remaining combined with the
ore, and forms metallic iron; but by this time the molten cinder is
present to prevent undue oxidation of the metal formed, and solid
carbon is still present in the mixture to play the same role, of
reducing protoxide of iron from the cinder, as the carbon of the cast
iron does in the ordinary puddling process. I have said that the cast
iron used as the material for puddling contains about 3 per cent. of
carbon; but in this process sufficient carbon is added to effect the
reduction of the ore to a metallic state, and leave enough in the mass
to play the part of the carbon of the cast iron when the metallic
stage has been reached.
It would be interesting to compare the Wilson with the numerous other
direct processes to which allusion has already been made, but there
have been so many of them, and the data concerning them are so
incomplete, that this is impossible. Two processes, however, the Blair
and the Siemens, have attracted sufficient attention, and are
sufficiently modern to deserve notice. In the Blair process a metallic
iron sponge was made from the ore in a closed retort, this sponge
cooled down in receptacles from which the air was excluded, to the
temperature of the atmosphere, then charged into a puddling furnace
and heated for working. In this way (and the same plan essentially has
been followed by other inventors), the metallic iron, in the finest
possible state of subdivision, is subjected to the more or less
oxidizing influences of the flame, without liquid slag to save it from
oxidation, and with no carbon present to again reduce the iron oxides
from the cinder after it is formed. The loss of metal is consequently
very large, but oxides of iron being left in the metal the blooms are
invariably "red short."
In the Siemens process pieces of ore of the size of beans or peas,
mixed with lime or other fluxing material, form the charge, which is
introduced into a rotating furnace; and when this charge has become
heated to a bright-red heat, small coal of uniform size is added in
sufficient quantity to effect the reduction of the ore.
The size of the pieces of the material employed prevents the intimate
mixture of the particles of iron with the particles of carbon, and
hence we would, on theoretical grounds, anticipate just what practice
has proved, viz., that the reduction is incomplete, and the resulting
metal being charged with oxides is red-short. In practice, blooms made
by this process have been so red-short that they could not be hammered
at all.
It would be impracticable in this process to employ ore and carbon in
as fine particles as Wilson does, as a very large portion of the
charge would be carried off by the draught, and a sticking of the
material to the sides of the rotating furnace could scarcely be
avoided. I do not imagine that a division of the material into
anything like the supposed size of molecules is necessary; we know
that the graphitic carbon in the pig-iron employed in puddling is not
so finely divided, but it is much smaller particles than bean or pea
size, and by approximating the size of the graphite particles in pig
iron, Wilson has succeeded in obtaining good results.
If we examine the utilization of the heat developed by the combustion
of a given quantity of coal in this process, and compare it with the
result of the combustion of an equivalent amount of fuel in a blast
furnace, we shall soon see the theoretical economy of the process. The
coal is burned on the grate of the puddling-furnace, to carbonic acid,
and the flame is more fully utilized than in an ordinary
puddling-furnace, for besides the ordinary hearth there is the second
or rear hearth, where additional heat is taken up, and then the
products of combustion are further utilized in heating the retorts in
which the ore is partly reduced. After this the heat is still further
utilized by passing it under the boilers for the generation of steam,
and the heat lost in the gases, when they finally escape, is very
small. In a blast furnace the carbon is at first burned only to
carbonic oxide, and the products of combustion issue mainly in this
form from the top of the furnace. Then a portion of the heat resulting
from the subsequent burning of these gases is pretty well utilized in
making steam to supply the power required about the works, but the
rest of the gas can only be utilized for heating the blast, and here
there is an enormous waste, the amount of heat returned to the furnace
by the heated blast being very small in proportion to the amount
generated by the burning of that portion of carbonic oxide expended in
heating it, and the gases escape from both the hot-blast and the
boilers at a high temperature.
In the direct process under consideration the fuel burned is more
completely utilized than in the puddling process, to which the cast
iron from the blast furnace is subjected to convert it into wrought
iron.
The economy claimed for this process, over the blast furnace and
puddling practice for the production of wrought iron, is that nearly
all the fuel used in the puddling operation is saved, and that with
about the same amount of fuel used in the blast furnace to produce a
ton of pig iron, a ton of wrought iron blooms can be made. I had no
opportunity of weighing the charges of ore and coal used, but I saw
the process in actual operation at Rockaway, N.J. The iron produced
was hammered up into good solid blooms, containing but little cinder.
The muck-bar made from the blooms was fibrous in fracture, and showed
every appearance of good iron. I am informed by the manager of the
Sanderson Brothers' steel works, at Syracuse, N.Y., that they
purchased blooms made by the Wilson process in 1881-1882, that _none_
of them showed red-shortness, and that they discontinued their use
only on account of the injurious action of the titanium they contained
on the melting pots. These blooms were made from magnetic sands from
the Long Island and Connecticut coasts.
[Illustration: NEW PROCESS FOR MAKING WROUGHT IRON FROM THE ORE.]
The drawing given shows the construction of the furnace employed. I
quote from the published description:
"The upper part, or deoxidizer, is supported on a strong
mantel plate resting on four cast iron columns.
"The retorts and flues are made entirely of fire-brick, from
special patterns. The outside is protected by a wrought iron
jacket made of No. 14 iron. The puddling furnace is of the
ordinary construction, except in the working bottom, which is
made longer to accommodate two charges of ore, and thus
utilize more of the waste heat in reducing the ore to metallic
iron.
"The operation of the furnace is as follows: The pulverized
ore is mixed with 20 per cent. of pulverized charcoal or coke,
and is fed into an elevator which discharges into the hopper
on the deoxidizer leading into the retorts marked C. These
retorts are proportioned so that they will hold ore enough to
run the puddling furnace 24 hours, the time required for
perfect deoxidation. After the retorts are filled, a fire is
started in the furnace, and the products of combustion pass up
through the main flue, or well, B, where they are deflected by
the arch, and pass out through suitable openings, as indicated
by arrows, into the down-takes marked E, and out through an
annular flue, where they are passed under a boiler.
"It will be noticed that the ore is exposed to the waste heat
on three sides of the retorts, and owing to the great surface
so exposed, the ore is very thoroughly deoxidized, and reduced
in the retorts before it is introduced into the puddling
furnace for final reduction. The curved cast iron pipes marked
D are provided with slides, and are for the purpose of
introducing the deoxidized ore into the second bottom of the
furnace. As before stated, the furnace is intended to
accommodate two charges of ore, and as fast as it is balled up
and taken out of the working bottom, the charge remaining in
the second bottom is worked up in the place occupied by the
first charge, and a _new_ charge is introduced. As fast as the
ore is drawn out from the retorts the elevator supplies a new
lot, so that the retorts are always filled, thus making the
process continuous."
The temperature of the charge in the deoxidizer is from 800° to 1,000°
F.--_Amer. Engineer._
* * * * *
SOME REMARKS ON THE DETERMINATION OF HARDNESS IN WATERS.
By HERBERT JACKSON.
Having had occasion some short time ago to examine a hard water which
owed half its hardness to salts of magnesium, I noticed that the soap
test, applied in the usual way, gave a result which differed very much
from that obtained by the quantitative estimation of calcium and
magnesium. A perfectly normal lather was obtained when soap had been
added in quantities sufficient to neutralize 14° of hardness, whereas
the water contained salts of calcium and magnesium equivalent, on
Clark's scale, to a hardness of 27°.
Although I was aware that similar observations had been made before, I
thought that it might be useful to determine the conditions under
which the soap test could not be depended upon for reliable results.
I found with waters containing calcium or magnesium alone that,
whenever salts of either of these metals were in solution in
quantities sufficient to give 23° of hardness on Clark's scale, no
dependence could be placed upon the results given by the soap test. In
the case of waters containing salts of both calcium and magnesium, I
found that if the salts of the latter metal were in solution in
quantities sufficient to give more than 10° of hardness, no evidence
could be obtained of their presence so long as the salts of calcium in
the same water exceeded 6°; in such a case a perfect and permanent
lather was produced when soap had been added equivalent to 7° of
hardness.
If any water be diluted so as to reduce the proportions of the salts
of calcium and magnesium below those stated above, perfectly reliable
results will of course be obtained.
Instead of dilution I found that heating the water to about 70° C. was
sufficient to cause a complete reaction between the soap and the salts
of calcium and magnesium, even if these were present in far larger
quantities than any given here.
The experiments so far had all been made with a solution of Castile
soap of the strength suggested by Mr. Wanklyn in his book on "Water
Analysis." My attention was next directed to the use of any one of the
compounds of which such a soap is composed. I commenced with sodium
oleate, and found that by employing this substance in a moderately
pure condition, perfectly reliable results could be obtained in very
hard waters without the trouble of either diluting or heating. I was
unable to try sodium stearate directly because of the slight
solubility of this substance in cold water or dilute alcohol; but I
found that a mixture of sodium oleate and stearate behaved in exactly
the same manner as the Castile soap.
I am not prepared at present to state the exact reaction which takes
place between salts of calcium and magnesium and a compound soap
containing sodium oleate and stearate. I publish these results because
I have not noticed anywhere the fact that some waters show a greater
hardness with soap when their temperatures approach the boiling point
than they do at the average temperature of the air, it being, I
believe, the ordinary impression that cold water wastes more soap than
hot water before a good and useful lather can be obtained, whereas
with very many waters the case is quite the reverse. Neither am I
aware at present whether it is well known that the use of sodium
oleate unmixed with sodium stearate dispenses with the process of
dilution even in very hard waters.--_Chem. News._
* * * * *
THE DENSITY AND PRESSURE OF DETONATING GAS MIXTURES.
MM. Berthelot and Vielle have recently been studying the influence of
the density of detonating gaseous mixtures upon the pressure
developed. The measure of pressure developed by the same gaseous
system, taken under two initial states of different density to which
the same quantity of heat is communicated, is an important matter in
thermodynamics. If the pressures vary in the same ratio as the
densities, we may conclude, independently of all special hypotheses on
the laws of gases, first, that the specific heat of the system is
independent of its density (that is to say, of its initial pressure),
and depends only on the absolute temperature, whatever that may mean;
and secondly, that the relative variation of the pressure at constant
volume, produced by the introduction of a determinate quantity of
heat, is also independent of the pressure, and a function only of the
temperature. Lastly, the pressure itself will vary proportionally with
the absolute temperature, as defined by the theory of a perfect gas,
and will serve to determine it. MM. Berthelot and Vielle operated with
a bomb, at first kept at ordinary temperatures in the air, and
afterward heated in an oil bath to 153 deg. Cent. They also employed
isomeric mixtures of the gases; methylic ether, cyanogen, hydrogen,
acetylene, and other gases were experimented upon, and the general
conclusions are as follows: 1. The same quantity of heat being
furnished to a gaseous system, the pressure of the system varies
proportionally to the density of the system. 2. The specific heat of
the gas is sensibly independent of the density as well toward very
high temperatures as about deg. Cent. This is all true for densities
near to those that the gas possesses cold under normal pressure, and
which varied in the experiment to double the original value. 3. The
pressure increases with the quantity of heat furnished to the same
system. 4. The apparent specific heat increases parallel with this
quantity of heat. These conclusions are independent of all hypotheses
on the nature and laws of gases, and were simply drawn from the
experiments in question.
* * * * *
TURKISH BATHS FOR HORSES.
The Turkish bath has become an established institution in this
country; men of all classes now use it for sanitary as well as
remedial purposes. Athletes of various descriptions find it invaluable
in "training," and all the distinguished jockeys and light weights
keep themselves in condition by its use.
It was thought probable that what was good for man might also be good
for the horse, and the fact has been proved. Messrs. Pickford, the
eminent carriers, in their hospital for horses at Finchley, have had a
bath in operation over eleven years, and find the horses derive great
benefit from its use. The bath is put in operation three days a week,
and is administered to over twenty horses in this time. The value of
the bath having been thus proved, it is rather strange that it has not
been more generally adopted by the large carrying firms. However, the
Great Northern Railway Company at their new hospital for horses at
Totteridge, are erecting a very complete Turkish bath. It consists of
three rooms. First, a large wash room or grooming room, from which is
entered the first hot room, or tepidarium, from 140° to 150° Fahr.;
from this room, the horse, after being thoroughly acclimated, can, if
necessary, pass to the hottest room, or calidarium, from 160° to 170°
Fahr., and without any turning round can pass on into the grooming and
washing room again. This last room is slightly heated from the two
other rooms, and in each are stocks in which the animal can he
fastened if required. The heating is done most economically by
Constantine's convoluted stove, and thorough ventilation is secured
from the large volume of hot air constantly supplied, which passes
through the baths, and as it becomes vitiated is drawn off by
specially designed outlets. The wash room is supplied with hot and
cold water, which can, of course, be mixed to any required
temperature.--_Building News._
[Illustration]
||
|+-------------------------------------------------------+
|+-------------------++---__-------____------------__---+|
|| ||FOUL AIR FOUL AIR FOUL AIR||
|| || ||
|| || ||
|| || ============== ||
|| / / ||
|| / / 1ST HOT ROOM ||
|| / / ||
|| / / ============== ||
|| || ||
/ =======+ || ||
/ || || CURTAIN||
WASHING ROOM|| |+=========================== =||
\ || || ||
\ =======+ || ||
|| || ||
|| \ \ ============== ||
|| \ \ ||
|| \ \ 2ND HOT ROOM || FRESH
|| \ \ || / AIR
|| || ============== ||==
|| || +======|| |
|| || | WARM || |
|| ||FOUL AIR FOUL AIR| AIR || |
|+-------------------++---__--+===+---------__----------+|==
|+----------------------------|_|_|---------------------+|
|| | ||||| | ||
|| | ||||| | ||
|| |============ S T O K E R Y ||
|| || ||
|| || ||
|| |+-----------------------------------||
+-------------------------------------+
* * * * *
MIRYACHIT, A NEWLY DESCRIBED DISEASE OF THE NERVOUS SYSTEM, AND
ITS ANALOGUES.[1]
[Footnote 1: Read before the New York Neurological Society,
February 5, 1884.]
By WILLIAM A. HAMMOND, M.D., Surgeon-General, U.S. Army (Retired
List); Professor of Diseases of the Mind and Nervous System in the New
York Post-Graduate Medical School and Hospital.
In a very interesting account of a journey from the Pacific Ocean
through Asia to the United States, by Lieutenant B.H. Buckingham and
Ensigns George C. Foulk and Walter McLean,[2] United States navy, I
find an affection of the nervous system described which, on account of
its remarkable characteristics, as well as by reason of certain known
analogies, I think should be brought to the special notice of the
medical profession. I quote from the work referred to, the following
account of this disease. The party is on the Ussuri River not far from
its junction with the Amur in Eastern Siberia: "While we were walking
on the bank here we observed our messmate, the captain of the general
staff (of the Russian army), approach the steward of the boat
suddenly, and, without any apparent reason or remark, clap his hands
before his face; instantly the steward clapped _his_ hands in the same
manner, put on an angry look, and passed on. The incident was somewhat
curious, as it involved a degree of familiarity with the steward
hardly to have been expected. After this we observed a number of queer
performances of the steward, and finally comprehended the situation.
It seemed that he was afflicted with a peculiar mental or nervous
disease, which forced him to imitate everything suddenly presented to
his senses. Thus, when the captain slapped the paddle-box suddenly in
the presence of the steward, the latter instantly gave it a similar
thump; or, if any noise were made suddenly, he seemed compelled
against his will to imitate it instantly, and with remarkable
accuracy. To annoy him, some of the passengers imitated pigs grunting,
or called out absurd names; others clapped their hands and shouted,
jumped, or threw their hats on the deck suddenly, and the poor
steward, suddenly startled, would echo them all precisely, and
sometimes several consecutively. Frequently he would expostulate,
begging people not to startle him, and again would grow furiously
angry, but even in the midst of his passion he would helplessly
imitate some ridiculous shout or motion directed at him by his
pitiless tormenters. Frequently he shut himself up in his pantry,
which was without windows, and locked the door, but even there he
could be heard answering the grunts, shouts, or pounds on the bulkhead
outside. He was a man of middle age, fair physique, rather intelligent
in facial expression, and without the slightest indication in
appearance of his disability. As we descended the bank to go on board
the steamer, some one gave a loud shout and threw his cap on the
ground; looking about for the steward, for the shout was evidently
made for his benefit, we saw him violently throw his cap, with a
shout, into a chicken-coop, into which he was about to put the result
of his foraging expedition among the houses of the stanitza.
[Footnote 2: "Observations upon the Korean Coast, Japanese-Korean
Ports, and Siberia, made during a journey from the Asiatic
Station to the United States, through Siberia to Europe, June 3
to September 8, 1882." Published by the United States Navy
Department, Washington, 1883, pp. 51.]
"We afterward witnessed an incident which illustrated the extent of
his disability. The captain of the steamer, running up to him,
suddenly clapping his hands at the same time, accidentally slipped and
fell hard on the deck; without having been touched by the captain, the
steward instantly clapped his bands and shouted, and then, in
powerless imitation, he too fell as hard and almost precisely in the
same manner and position as the captain. In speaking of the steward's
disorder, the captain of the general staff stated that it was not
uncommon in Siberia; that he had seen a number of cases of it, and
that it was commonest about Yakutsk, where the winter cold is extreme.
Both sexes were subject to it, but men much less than women. It was
known to Russians by the name of 'miryachit'".
So far as I am aware--and I have looked carefully through several
books of travel in Siberia--no account of this curious disease has
been hitherto published.
The description given by the naval officers at once, however, brings
to mind the remarks made by the late Dr. George M. Beard, before the
meeting of the American Neurological Association in 1880, relative to
the "Jumpers" or "Jumping Frenchmen" of Maine and northern New
Hampshire.[3]
[Footnote 3: "Journal of Nervous and Mental Diseases," vol. vii.,
1880, p. 487.]
In June, 1880, Dr. Beard visited Moosehead Lake, found the "Jumpers,"
and experimented with them. He ascertained that whatever order was
given them was at once obeyed. Thus, one of the jumpers who was
sitting in a chair with a knife in his hand was told to throw it, and
he threw it quickly, so that it stuck in a beam opposite; at the same
time he repeated the order to throw it with a cry of alarm not unlike
that of hysteria or epilepsy. He also threw away his pipe, which he
was filling with tobacco, when he was slapped upon the shoulder. Two
jumpers standing near each other were told to strike, and they struck
each other very forcibly. One jumper, when standing by a window, was
suddenly commanded by a person on the other side of the window to
jump, and he jumped up half a foot from the floor, repeating the
order. When the commands are uttered in a quick, loud voice, the
jumper repeats the order. When told to strike he strikes, when told to
throw he throws whatever he may happen to have in his hand. Dr. Beard
tried this power of repetition with the first part of the first line
of Virgil's "Æneid" and the first part of the first line of Homer's
"Iliad," and out-of-the-way words of the English language with which
the jumper could not be familiar, and he repeated or echoed the sound
of the word as it came to him in a quick, sharp voice, at the same
time he jumped, or struck, or threw, or raised his shoulders, or made
some other violent muscular motion. They could not help repeating the
word or sound that came from the person that ordered them, any more
than they could help striking, dropping, throwing, jumping, or
starting; all of these phenomena were indeed but parts of the general
condition known as jumping. It was not necessary that the sound should
come from a human being; any sudden or unexpected noise, as the
explosion of a gun or pistol, the falling of a window, or the slamming
of a door--provided it was unexpected and loud enough--would cause
these jumpers to exhibit some one or all of these phenomena. One of
these jumpers came very near cutting his throat, while shaving, on
hearing a door slam. They had been known to strike their fists against a
red-hot stove, to jump into the fire and into water. They could not
help striking their best friend if near them when ordered. The noise
of a steam whistle was especially obnoxious to them. One of these
jumpers, when taking some bromide of sodium in a tumbler, was told to
throw it, and he dashed the tumbler upon the floor. It was dangerous
to startle them in any way when they had an ax or an knife in their
hands. All of the jumpers agreed that it tired them to be jumped, and
they dreaded it, but they were constantly annoyed by their companions.
From this description it will at once, I think, be perceived that
there are striking analogies between "miryachit" and this disorder of
the "Jumping Frenchmen" of Maine. Indeed, it appears to me that, if
the two affections were carefully studied, it would be found that they
were identical, or that, at any rate, the phenomena of the one could
readily be developed into those of the others. It is not stated that
the subjects of miryachit do what they are told to do. They require an
example to reach their brains through the sense of sight or that of
hearing, whereas the "Jumpers" do not apparently perform an act which
is executed before them, but they require a command. It seems,
however, that a "Jumper" starts whenever any sudden noise reaches his
ears.
In both classes of cases a suggestion of some kind is required, and
then the act takes place independently of the will. There is another
analogous condition known by the Germans as _Schlaftrunkenheit_, and
to English and American neurologists as somnolentia, or
sleep-drunkenness. In this state an individual, on being suddenly
awakened, commits some incongruous act of violence, ofttimes a murder.
Sometimes this appears to be excited by a dream, but in others no such
cause could be discovered.
Thus, a sentry fell asleep during his watch, and, being suddenly
aroused by the officer in command, attacked the latter with his sword,
and would have killed him but for the interposition of the bystanders.
The result of the medical examination was that the act was
involuntary, being the result of a violent confusion of mind
consequent upon the sudden awaking from a profound sleep. Other cases
are cited by Wharton and Stille in their work on medical
jurisprudence, by Hoffbauer, and by myself in "Sleep and its
Derangements."
The following cases among others have occurred in my own experience:
A gentleman was roused one night by his wife, who heard the
street-door bell ring. He got up, and, without paying attention to
what she said, dragged the sheets off of the bed, tore them hurriedly
into strips, and proceeded to tie the pieces together. She finally
succeeded in bringing him to himself, when he said he had thought the
house was on fire, and he was providing means for their escape. He did
not recollect having had any dream of the kind, but was under the
impression that the idea had occurred to him at the instant of his
awaking.
Another was suddenly aroused from a sound sleep by the slamming of a
window-shutter by the wind. He sprang instantly from his bed, and,
seizing a chair that was near, hurled it with all his strength against
the window. The noise of the breaking of glass fully awakened him. He
explained that he imagined some one was trying to get into the room
and had let his pistol fall on the floor, thereby producing the noise
which had startled him.
In another case a man dreamed that he heard a voice telling him to
jump out of the window. He at once arose, threw open the sash, and
jumped to the ground below, fortunately only a distance of about ten
feet, so that he was not injured beyond receiving a violent shock.
Such a case as this appears to me to be very similar to those
described by Dr. Beard in all its essential aspects.
A few years ago I had a gentleman under my charge who would attempt to
execute any order given him while he was asleep by a person
whispering into his ear. Thus, if told in this way to shout, he
shouted as loud as he could; if ordered to get up, he at once jumped
from the bed; if directed to repeat certain words, he said them, and
so on.
I am not able to give any certain explanation of the phenomena of
miryachit or of the "Jumpers," or of certain of those cases of
sleep-drunkenness which seem to be of like character. But they all
appear to be due to the fact a motor impulse is excited by perceptions
without the necessary concurrence of the volition of the individual to
cause the discharge. They are, therefore, analogous to reflex actions,
and especially to certain epileptic paroxysms due to reflex
irritations. It would seem as though the nerve cells were very much in
the condition of a package of dynamite or nitro glycerin, in which a
very slight impression is sufficient to effect a discharge of nerve
force. They differ, however, from the epileptic paroxysm in the fact
that the discharge is consonant with the perception--which is in these
cases an irritation--and is hence an apparently logical act, whereas
in epilepsy the discharge is more violent, is illogical, and does not
cease with the cessation of the irritation.
Certainly the whole subject is of sufficient importance to demand the
careful study of competent observers.
* * * * *
THE GUM DISEASE IN TREES.[1]
[Footnote 1: Communicated to the _Medical Times_ by Sir James Paget.]
An essay by Dr. Beijerinck, on the contagion of the gum disease in
plants, lately published by the Royal Academy of Sciences at
Amsterdam, contains some useful facts. The gum disease (_gummosis,
gum-flux)_ is only too well known to all who grow peaches, apricots,
plums, cherries, or other stone fruits. A similar disease produces gum
arabic, gum tragacanth, and probably many resins and gum resins. It
shows itself openly in the exudation of thick and sticky or hard and
dry lumps of gum, which cling on branches of any of these trees where
they have been cracked or wounded through the bark. Dr. Beijerinck was
induced to make experimental inoculations of the gum disease by
suspicions that, like some others observed in plants, it was due to
bacteria. He ascertained that it is in a high degree contagious, and
can easily be produced by inserting the gum under the edge of a wound
through the bark of any of the trees above named. The observation that
heated or long boiled pieces of gum lose their contagious property
made it most probable that a living organism was concerned in the
contagions; and he then found that only those pieces of the gum
conveyed contagion in which, whether with or without bacteria, there
were spores of a relatively highly organized fungus, belonging to the
class of Ascomycetes; and that these spores, inserted by themselves
under the bark, produced the same pathological changes as did the
pieces of gum. The fungus thus detected, was examined by Professor
Oudemans, who ascertained it to be a new species of Coryneum, and has
named it _Coryneum Beijerincki_. The inoculation experiments are best
made by means of incisions through the bark of young branches of
healthy peach trees or cherry trees, and by slightly raising the cut
edge of the bark and putting under it little bits of gum from a
diseased tree of the same kind. In nearly every instance these wounds
become the seats of acute gum disease, while similar wounds in the
same or other branches of the same tree, into which no gum is
inserted, remain healthy, unless, by chance, gum be washed into them
during rain. The inoculation fails only when the inserted pieces of
gum contain no Coryneum. By similar inoculations similar diseases can
be produced in plum, almond, and apricot trees, and with the gum of
any one of these trees any other can be infected; but of many other
substances which Beijerinck tried, not one produced any similar
disease. The inoculation with the gum is commonly followed by the
death of more or less of the adjacent structures; first of the bark,
then of the wood. Small branches or leaf stalks thus infected in
winter, or in many places at the same time, may be completely killed;
but, in the more instructive experiments the first symptom of the gum
disease is the appearance of a beautiful red color around the wound.
It comes out in spots like those which often appear spontaneously on
the green young branches of peach trees that have the gum disease; and
in these spots it is usual to find Coryneum stromata or mycelium
filaments. The color is due to the formation of a red pigment in one
or more of the layers of the cells of the bark. But in its further
progress the disease extends beyond the parts at which the Coryneum or
any structures derived from it can be found; and this extension,
Beijerinck believes, is due to the production of a fluid of the nature
of a ferment, produced by the Coryneum, and penetrating the adjacent
structures. This, acting on the cell walls, the starch granules, and
other constituents of the cells, transforms them into gum, and even
changes into gum the Coryneum itself, reminding the observer of the
self-digestion of a stomach.
In the cells of the cambium, the same fluid penetrating unites with
the protoplasm, and so alters it that the cells produced from it form,
not good normal wood, but a morbid parenchymatous structure. The cells
of this parenchyma, well known among the features of gum disease, are
cubical or polyhedral, thin walled, and rich in protoplasm. This, in
its turn, is transformed into gum, such as fills the gum channels and
other cavities found in wood, and sometimes regarded as gum glands.
And from this also the new ferment fluid constantly produced, and
tracking along the tissues of the branches, conveys the Coryneum
infection beyond the places in which its mycelium can be found.
* * * * *
DRINKSTONE PARK.
Drinkstone has long been distinguished on account of the successful
cultivation of remarkable plants. It lies some eight miles southeast
from Bury St. Edmund's, and is the seat of T.H. Powell, Esq. The
mansion or hall is a large old-fashioned edifice, a large portion of
its south front being covered by a magnificent specimen of the
Magnolia grandiflora, not less than 40 feet in height, while other
portions of its walls are covered with the finest varieties of
climbing roses and other suitable plants. The surrounding country,
although somewhat flat, is well wooded, and the soil is a rich loam
upon a substratum of gravel, and is consequently admirably suited to
the development of the finer kinds of coniferous and other ornamental
trees and shrubs, so that the park and grounds contain a fine and well
selected assortment of such plants.
[Illustration: THE SNOWFLAKE, LEUCOJUM VERNUM, AT DRINKSTONE
PARK.]
Coniferous trees are sometimes considered as out of place in park
scenery; this, however, does not hold good at Drinkstone, where Mr.
Powell has been displayed excellent taste in the way of improving the
landscape and creating a really charming effect by so skillfully
blending the dressed grounds with the rich greensward of the park
that it is not easy to tell where the one terminates or the other
commences.
The park, which covers some 200 acres, including a fine lake over
eight acres in extent, contains also various large groups or clumps of
such species as the Sequoia gigantea, Taxodium sempervirens, Cedres
deodora, Picea douglasii, Pinsapo, etc., interspersed with groups of
ornamental deciduous trees, producing a warm and very pleasing effect
at all seasons of the year. Among species which are conspicuous in the
grounds are fine, well-grown examples of Araucaria imbricata, some 30
feet high; Cedrus deodara, 60 feet in height; Abies pinsapo, 40 feet;
and fine specimens of Abies grandis, A. nobilis, and A. nordmanniana,
etc., together with Abies albertiana or mertensiana, a fine,
free-growing species; also Libocedrus gigantea, Thuiopsis borealis,
Thuia lobbii, Juniperus recurva, Taxas adpressa, fine plants; with
fine golden yews and equally fine examples of the various kinds of
variegated hollies, etc.
[Illustration: ODONTOGLOSSUM ROSSI MAJOR VAR. RUBESCENS, AT DRINKSTONE
PARK.]
Particular attention is here paid to early spring flowers. Drinkstone
is also celebrated as a fruit growing establishment, more particularly
as regards the grape vine; the weight and quality of the crops of
grapes which are annually produced here are very remarkable.--_The
Gardeners' Chronicle._
* * * * *
ON THE CHANGES WHICH TAKE PLACE IN THE CONVERSION OF HAY INTO
ENSILAGE.
By FREDK. JAS. LLOYD, F.C.S., Lecturer on Agriculture, King's
College.
The recently published number of the _Royal Agricultural Society's
Journal_ contains some information upon the subject of silage which
appears to me of considerable interest to those chemists who are at
present investigating the changes which take place in the conversion
of grass into silage. The data[1] are, so far as I know, unique, and
though the analytical work is not my own, yet it is that of an
agricultural chemist, Mr. A. Smetham, of Liverpool, whose work I know
from personal experience to be thoroughly careful and reliable. I have
therefore no hesitation in basing my remarks upon it.
[Footnote 1: _Royal Agricultural Society's Journal_, vol. xx.,
part i., pp. 175 and 380.]
We have here for the first time an accurate account of the quantity of
grass put into a silo, of the quantity of silage taken out, and of the
exact composition both of the grass and resulting silage. I desire
merely to place myself in the position of, so to speak, a "chemical
accountant."
The ensilage has been analyzed at three depths, or rather in three
layers, the first being 1 foot, the second 1 ft. to 1 ft. 6 in., and
the third 1 ft. 6 in. to 2 ft. from the bottom of the silo. By
doubling the figures of the bottom layer analysis, adding these to the
second and third layer analysis, and dividing by 4, we obtain a fair
representation of the average composition of the silage taken
throughout the silo, for by so doing we obtain the average of the
analyses of each 6-inch layer of silage. The results of the analyses
are as follows, calculated on the dry matter. The moisture was
practically the same, being 70.48 per cent, in the grass and 72.97 in
the silage.
_Composition of Grass and Silage (dried at 100°C.)._
Grass. Ensilage.
Fat (ether extract) 2.80 5.38
Soluble albuminous compounds 3.06 5.98
Insoluble albuminous compounds 6.94 3.77
Mucilage, sugar, and extractives, etc. 11.65 4.98
Digestible fiber 36.24 33.37
Indigestible woody fiber 32.33 31.79
------- -------
93.02 85.27
Soluble mineral matters 5.24 12.62
Insoluble mineral matters 1.74 2.11
------- -------
100.00 100.00
The striking difference in the mineral matter of the grass and silage
I will merely draw attention to; it is not due to the salt added to
the silage. I may say, however, that other analysts and I myself have
found similar striking differences. For instance, Prof. Kinch[2]
found in grass 8.50 per cent. mineral matter, in silage 10.10 per
cent., which, as be points out, is equivalent, to a "loss of about 18
per cent. of combustible constituents"--a loss which we have no proof
of having taken place. In Mr. Smetham's sample the loss would have to
be 50 per cent., which did not occur, and in fact is not possible.
What is the explanation?
[Footnote 2: _Journ. Chem. Society_, March, 1884, p. 124.]
I am, however, considering now the organic constituents. Calculating
the percentages of these in the grass and silage, we obtain the
following figures:
_Percentage Composition of Organic Compounds._
Grass. Ensilage.
Fat (ether extract) 3.01 6.31
Soluble albuminous compounds 8.29} {7.01
}10.75 11.43{
Insoluble " " 7.46} {4.42
Mucilage, sugar, and extractives 12.52 5.84
Digestible fiber 38.96 39.14
Indigestible woody fiber 34.76 37.28
------- -------
100.00 100.00
The difference in the total nitrogen in the grass and silage is equal
to 0.68 per cent. of albuminoids. Practically it is a matter of
impossibility that the nitrogen could have increased in the silo, and
it will be a very safe premise upon which to base any further
calculations that the total amount of nitrogen in the silage was
identical with that in the grass. There may have been a loss, but
that is not yet proved. Arguing then upon the first hypothesis, it is
evident that 100 parts of the organic matters of silage represent more
than 100 parts of the organic matter of grass, and by the equation we
obtain 10.75:11.43 :: 100:106 approximately. If now we calculate the
composition of 106 parts organic matter of grass, it will represent
exactly the organic matter which has gone to form 100 parts of that
present in silage.
The following table gives these results, and also the loss or gain in
the various constitutents arising from the conversion into silage:
_Organic Matter_.
In 106 pts. In 100 pts. Loss or
Grass. Silage. Gain.
Fat (ether extract) 3.19 6.31 +3.12
Soluble albuminous compounds 3.49 7.01 +3.52
Insoluble " " 7.91 4.42 -3.49
Mucilage 13.27 5.84 -7.43
Digestible Fiber 41.30 39.14 -2.16
Indigestible woody fiber 36.84 37.28 +0.44
------- -------
106.00 100.00
These calculations show, provided my reasoning be correct, that the
chief changes which take place are in the albuminous compounds, which
has already been pointed out by Professors Voelcker, Kinch, and
others; and in the starch, gum, mucilage, sugar, and those numerous
bodies termed extractives, which was to be expected. But they show
most conclusively that the "decrease in the amount of indigestible
fiber and increase in digestible" so much spoken of is, so far as our
present very imperfect methods of analyzing these compounds permit us
to judge, a myth; and I have not yet found any sufficient evidence to
support this statement. A loss, then, of 6 parts of organic matter out
of every 106 parts put into the silo has in this instance taken place,
due chiefly to the decomposition of starch, sugar, and mucilage, etc.
And as the grass contained 70 parts of water when put into the silo,
the total loss would only be 1.7 per cent. of the total weight. This
theoretical deduction was found by practical experience correct, for
Mr. Smith, agent to Lord Egerton, upon whose estate this silage was
made, in his report to Mr. Jenkins says the "actual weight out of the
silo corresponds exactly with the weight we put into the same."
In my judgment these figures are of interest to the agricultural
chemist for many reasons. First, they will clear the ground for future
workers and eliminate from their researches what would have greatly
complicated them--changes in the cellulose bodies.
Secondly, they are of interest because our present methods of
distinguishing between and estimating digestible and indigestible
fiber is most rough, and probably inaccurate, and may not in the least
represent the power of an animal--say a cow--to digest these various
substances; and most of us know that when a new method of analysis
becomes a necessity, a new method is generally discovered. Lastly,
they are of interest to the agriculturist, for they point out, I
believe for the first time, the exact amount of loss which grass--or
at least one sample--has undergone in conversion into silage, and also
that much of the nitrogenous matter is changed, and so far as we know
at present, lost its nutritive value. This, however, is only comparing
silage with grass. What is wanted is to compare silage with hay--both
made out of the same grass. Then, and then only, will it be possible
to sum up the relative advantages or disadvantages of the two methods
of preserving grass as food for cattle.--_Chem. News_.
* * * * *
THE ILLUMINATING POWER OF ETHYLENE.
Dr. Percy Frankland has obtained results which may be thus briefly
summarized: (1.) That pure ethylene, when burnt at the rate of 5 cubic
feet per hour from a Referee's Argand burner, emits a light of 68.5
standard candles. (2.) That the illuminating power of equal volumes of
mixtures of ethylene with either hydrogen carbonic oxide or
marsh-gas is less than that of pure ethylene. (3.) That when the
proportion of ethylene in such mixtures is above 63 per cent. the
illuminating power of the mixture is but slightly affected by the
nature of the diluent. When, on the other hand, the proportion of
ethylene in such mixtures is low, the illuminating power of the
mixture is considerably the highest when marsh-gas is the diluent, and
the lowest when the ethylene is mixed with carbonic oxide. (4.) That
if 5 cubic feet of ethylene be uniformly consumed irrespectively of
the composition of the mixture, the calculated illuminating power is
in every case equal to or actually greater than that of pure ethylene
until a certain degree of dilution is attained. This intrinsic
luminosity of ethylene remains almost constant when the latter is
diluted with carbonic oxide, until the ethylene forms only 40 per
cent. of the mixture, after which it rapidly diminishes to zero when
the ethylene forms only 20 per cent. of the mixture. When the ethylene
is diluted with hydrogen, its intrinsic luminosity rises to 81 candles
when the ethylene constitutes 30 per cent. of the mixture, after which
it rapidly falls to zero when the ethylene amounts to only 10 per
cent. In the case of mixtures of ethylene and marsh-gas, the intrinsic
luminosity of the former is augmented with increasing rapidity as the
proportion of marsh gas rises, the intrinsic luminosity of ethylene,
in a mixture containing 10 per cent. of the latter, being between 170
and 180 candles.
* * * * *
DIFFRACTION PHENOMENA DURING TOTAL SOLAR ECLIPSES.[1]
[Footnote 1: A paper read before the American Astronomical
Society, May 5, 1884.]
By G.D. Hiscox.
The reality of the sun's corona having been cast in doubt by a leading
observer of the last total eclipse, who, from the erratic display
observed in the spectroscope, has declared it a subjective phenomenon
of diffraction, has led me to an examination and inquiry as to the
bearing of an obscurely considered and heretofore only casually
observed phenomenon seen to take place during total solar eclipses.
This phenomenon, it seems to me, ought to account for, and will
possibly satisfy, the spectroscopic conditions observed just before,
during, and after totality; which has probably led to the epithet used
by some leading observers--"the fickle corona." The peculiar
phenomenon observed in the spectroscope, the flickering bands or lines
of the solar spectrum flashing upon and across the coronal spectrum,
has caused no little speculation among observers.
The diffraction or interference bands projected by the passage of a
strong beam of light by a solid body, as discovered long since by
Grimaldi, and investigated later by Newton, Fresnel, and Fraunhofer,
are explained and illustrated in our text books; but the grand display
of this phenomenon in a total solar eclipse, where the sun is the
source of light and the moon the intercepting body, has as yet
received but little attention from observers, and is not mentioned to
my knowledge in our text books.
In the instructions issued from the United States Naval Observatory
and the Signal Office at Washington for the observation of the eclipse
of July 29, 1878, attention was casually directed to this phenomenon,
and a few of the observers at Pike's Peak, Central City, Denver, and
other places have given lucid and interesting descriptions of the
flight of the diffraction bands as seen coursing over the face of the
earth at the speed of the moon's shadow, at the apparent enormous
velocity of thirty-three miles per minute, or fifty times the speed of
a fast railway train.
From a known optical illusion derived from interference or fits of
perception, as illustrated in quick moving shadows, this great speed
was not realized to the eye, as the observed motion of these shadows
was apparently far less rapid than their reality.
The ultra or diffraction bands outside of the shadow were distinctly
seen and described by Mr. J.E. Keeler at Central City, both before and
after totality. He estimates the shadow bands at 8 inches wide and 4
feet apart.
Professor E.S. Holden, also at Central City, estimated the dark bands
as about 3 feet apart, and variable.
From estimates which he obtained from other observers of his party,
the distances between the bands varied from 6 to l½ feet, but so
quickly did they pass that they baffled all attempts to count even the
number that passed in one second.
He observed the time of continuance of their passage from west to east
as forty-eight seconds, which indicates a width of 33 miles of
diffraction bands stretching outward from the edge of the shadow to
the number of many thousands.
Mr. G.W. Hill, at Denver, a little to the north of the central track
of the shadow, observed the infra or bands within the shadow, alluding
to the fact that they must be moving at the same rate as the shadow,
although their apparent motion was much slower, or like the shadows of
flying clouds. He attributes the discrepancy to optical illusion.
At Virginia City the _colors_ of the _ultra_ bands were observed, and
estimated at five seconds' duration from the edge of the shadow, which
is equal to about 4 miles in width. These are known to be the
strongest color bands in the diffraction spectrum, which accounts for
their being generally observed.
Mr. W.H. Bush, observing at Central City, in a communication to Prof.
Holden alludes to the brilliancy of the colors of these bands as seen
through small clouds floating near the sun's place during totality,
and of the rapid change of their rainbow colors as observed dashing
across the clouds with the rapidity of thought.
All of these bands, both ultra and infra, as seen in optical
experiments, are colored in reverse order, being from violet to red
for each band outward and inward from the edge of the shadow.
It is very probable that the velocity of the passage of all the bands
during a total eclipse very much modifies the distinctness of the
colors or possibly obliterates them by optically blending so as to
produce the dull white and black bands which occupied so large a
portion of this grand panorama.
The phenomenon of these faint colored bands, with the observed light
and dark shadows, may be attributed to one or all of the following
causes:
1. A change in the direction of a small portion of the sun's light
passing by the solid body of the moon, it being deflected outward by
repulsion or reflection from its surface, and other portions being
deflected inward after passing the body by mutual repulsion of its own
elements toward a _light vacuum_ or space devoid of the element of
vibration.
2. The colored spectral bands being the direct result of the property
of interference, or the want of correspondence of the wave lengths due
to divergence; the same phenomenon being also observed in convergent
light. This is practically illustrated in the hazy definition of the
reduced aperture of telescopes, and its peculiarities shown in the
spectral rings within and beyond the focus.
3. Chromatic dispersion by our atmosphere, together with selective
absorption, also by our atmosphere and its vapors, have been suggested
as causes in this curious and complicated phenomena.
In none of the reports descriptive of the phenomena of polarization of
the corona is there the slightest allusion to the influence that the
diffraction bands may possibly have in modifying or producing the
various conditions of polarization observed; although these
observations have been made and commented upon during the past
twenty-five years.
Investigations now in progress of the modifying relation of the
phenomenon of diffraction in its effect upon not only the physical
aspect of the corona, but also in some strange spectroscopic anomalies
that have been observed near the sun at other times than during a
total solar eclipse, will, it is hoped, result in a fuller
interpretation of the physical nature of one of the grandest elements
of creation--_light_; let there be more of it.
* * * * *
A CATALOGUE containing brief notices of many important scientific
papers heretofore published in the SUPPLEMENT, may be had gratis at
this office.
* * * * *
The Scientific American Supplement.
PUBLISHED WEEKLY.
Terms of Subscription, $5 a Year.
Sent by mail, postage prepaid, to subscribers in any part of the
United States or Canada. Six dollars a year, sent, prepaid, to any
foreign country.
All the back numbers of THE SUPPLEMENT, from the commencement, January
1, 1876, can be had. Price, 10 cents each.
All the back volumes of THE SUPPLEMENT can likewise be supplied. Two
volumes are issued yearly. Price of each volume, $2.50, stitched in
paper, or $3.50, bound in stiff covers.
COMBINED RATES--One copy of SCIENTIFIC AMERICAN and one copy of
SCIENTIFIC AMERICAN SUPPLEMENT, one year, postpaid, $7.00.
A liberal discount to booksellers, news agents, and canvassers.
MUNN &. CO., PUBLISHERS,
361 Broadway, New York, N.Y.
* * * * *
PATENTS.
In connection with the SCIENTIFIC AMERICAN, Messrs MUNN & Co. are
Solicitors of American and Foreign Patents, have had 39 years'
experience, and now have the largest establishment in the world.
Patents are obtained on the best terms.
A special notice is made in the SCIENTIFIC AMERICAN of all
Inventions patented through this Agency, with the name and residence
of the Patentee. By the immense circulation thus given, public
attention is directed to the merits of the new patent, and sales or
introduction often easily effected.
Any person who has made a new discovery or invention can ascertain,
free of charge, whether a patent can probably be obtained, by writing
to MUNN & Co.
We also send free our Hand Book about the Patent Laws, Patents,
Caveats, Trade Marks, their costs, and how procured. Address
MUNN & CO., 361 BROADWAY, NEW YORK.
Branch Office, cor. F and 7th Sts., Washington. D.C.
*** End of this LibraryBlog Digital Book "Scientific American Supplement, No. 441, June 14, 1884." ***
Copyright 2023 LibraryBlog. All rights reserved.