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Title: The Classification of Patents
Author: United States Patent Office
Language: English
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[Illustration: Department of the Interior]



Parts A and B of the following pages are designed to acquaint all
persons using the Patent Office classification with the principles upon
which the reclassification is proceeding.

Part C consists of a few tentative rules advanced with the notion of
fixing classification practice within the office in certain doubtful

Part D is intended to inform examiners reclassifying within examining
divisions respecting the initial procedure in reforming a class.



A. Introduction.                                                    1

  Past classifications of the U. S. Patent Office.                  1

  Beginning of revision.                                            2

  Precedents and authorities.                                       3

  Definition of scientific classification.                          4

B. Principles of the new classification of the Patent Office.       4

  Elements of a Patent Office classification.                       4

    Basis of classification.                                        5

      Art as a basis.                                               5

      Function or effect as a basis.                                7

      Structure as a basis.                                         8

    Division and arrangement.                                       9

      Infinitude of possible combinations.                         10

      Division and arrangement in the natural sciences.            10

      Difficulty of entitling a subclass corresponding to every
        combination.                                               11

      Expedients to reduce the number of subdivisions.             12

      Superiority and inferiority.                                 15

      Definite positional relationship of subdivisions.            16

      Indented schedules.                                          17

      Bifurcate division.                                          19

      Utility of arrangement according to resemblances.            19

    Definition.                                                    20

    Cross-references and search-notes.                             21

    Diagnosis to determine classification.                         22

      Claimed or unclaimed disclosure.                             22

      Diagnosis of pending applications.                           23

      Difficulties due to varying ideas of claims.                 25

C. Rules of classification.                                        26

  Basis of classification.                                         26

     1. "Art" as the basis.                                        26

     2. Operative or manipulative arts.                            26

     3. Structures.                                                26

     4. Composition of matter and formed stock.                    26

  Division and arrangement.                                        27

     5. Exhaustive division; miscellaneous subclass.               27

     6. Subclasses not to overlap.                                 27

     7. Subclasses of any group to be formed on one basis.         27

     8. Apparent exception to rules 6 and 7.                       27

     9. Relative position of subclasses.                           27

    10. Indention of subclasses.                                   29

    11. Different kinds of titles for subclasses.                  29

    12. Arrangement to limit search and cross references.          30

  Definition.                                                      30

    13. Tentative definition.                                      30

    14. How to define.                                             30

    15. Explanatory notes may sometimes displace definition.       31

  Cross-references and search-notes.                               31

    16. Impossibility of cross-referencing all disclosures.        31

    17. Occasion and direction of cross-referencing.               31

    18. Occasion and scope of search-notes.                        32

  Diagnosis to determine classification.                           32

    19. Patents diagnosed by claimed disclosure.                   32

    20. Patents diagnosed by most intensive claim.                 33

    21. Exception to rule 19, claim, for a part of a disclosed
      combination.                                                 33

    22. Exception to rule 19, claims for a part of a disclosed
      combination.                                                 33

    23. Exception to rule 19, generic combination old as matter
      of common knowledge.                                         34

    24. Exception to rule 19, article of manufacture defined
      only by material.                                            34

    25. Exception to rule 19, utilizing a composition.             34

    26. Exception to rule 19, utilizing a machine.                 34

    27. Patents having claims for several different
      inventions.                                                  35

    28. General rule of superiority between statutory kinds of
      invention.                                                   35

    29. Exception to rule 28.                                      35

    30. Process and apparatus.                                     36

    31. Article of manufacture and instrument for making a part
      of it or performing any minor act relative thereto.          36

    32. Process and product where search for the process would
      have to be made among machines.                              36

    33. Process and product where search for the process would
      have to be made among products.                              36

    34. Process of making a composition and the composition
      where the process is peculiarly adapted to make the
      composition.                                                 37

    35. Article of manufacture or composition and process for
      making one of the parts of the article or ingredients of
      the composition.                                             37

D. Procedure in reclassifying within examining divisions.          37

  1. General attitude.                                             37

  Procedure involving only cursory scrutiny of familiar patents--

    2. Consider wholes in forming tentative subdivisions of
      subclasses.                                                  38

    3. Write tentative definitions of subdivisions.                38

    4. Consider the significance of analogies found to traverse
      parts of two or more existing subclasses.                    38

    5. Arrange groups on parallel or accordant lines where
      practicable.                                                 38

    6. Watch for subcombinations deserving separate
      recognition.                                                 38

    7. Consider whether the groups collectively will constitute
      a proper class and their best correlation.                   38

  Procedure involving rigorous analysis--

    8. Diagnose each patent for original classification.           39

    9. Group and consider the disposition of patents deemed
      foreign to the class.                                        39

    10-15. Consider and indicate cross-referencing within
      and to and from the class.                               39, 40

  Note.                                                            40



Classification lies at the foundation of the mental processes. Without
the power of perceiving, recognizing resemblances, distinguishing
differences in things, phenomena and notions, grouping them mentally
according to those resemblances and differences, judgment is impossible,
nor could reason be exercised in proceeding from the known to the

       *       *       *       *       *

The facilitation and abbreviation of mental labor is at the bottom of
all mental progress. The reasoning faculties of Newton were not
different in qualitative character from those of a ploughman; the
difference lay in the extent to which they were exerted and the number
of facts which could be treated. Every thinking being generalizes more
or less, but it is the depth and extent of his generalizations which
distinguish the philosopher. Now it is the exertion of the classifying
and generalizing powers which thus enables the intellect of man to cope
in some degree with the infinite number and variety of natural phenomena
and objects. (Jevons, Principles of Science.)


As under the patent laws the people of the United States assume all the
risks in granting a patent for any means of the "useful arts," a
classification that will facilitate a judgment respecting the
patentability of any means presented to the Patent Office is of peculiar
moment. The enormous extent, diversity, and refinement of the useful
arts preclude the formation of a judgment on novelty within a reasonable
time, unless the necessary comparisons with known processes and
instruments have been previously made along the lines that searches must
follow and the results of such comparisons made available in a
classification. The vast majority of available disclosures of the arts
occur in patents. Hence the Patent Office classification must be
adjusted in the main to the analysis, diagnosis, and orderly arrangement
of the disclosures of patents.

For more than 80 years United States patents have been classified. The
first published classification, promulgated in 1830, comprised 6,170
patents, divided into 16 classes. The change from a registration to an
examination system in 1836 instigated a new classification in 22
classes, including 9,800 patents. The next came in 1868 with 36 classes,
including about 75,000 patents. On March 1, 1872, a revised
classification was adopted, comprising 145 classes, including 131,000
patents. This classification is said to have been planned by Dr. Edward
H. Knight. The placing of the patents in accordance with the schedule of
classes is said to have been done by the several examiners. The class
arrangement was purely alphabetical by class titles, and the number
designations followed the alphabetical order. The names of things to be
found in the several classes were arranged alphabetically under each
class title. No attempt was made to bring the titles of allied materials
into juxtaposition or to effect other definite arrangement with
reference to subject matter in the printed schedules. A consolidated
name index supplemented the list of names by classes.

This classification of 1872 is in part the classification that now
exists, many of the same class numbers and titles being still in use.
Examiners were apparently permitted to make changes in classification to
suit their convenience without notice until 1877. In that year a
revision of the published schedule was made by a committee, resulting in
the addition of 13 new classes, and examiners were ordered to transfer
patents in accordance with the new titles. The first classification
published with distinct subclasses appeared in 1880. From that time
until 1898 the classification grew by addition and subdivision of
classes to suit the ends of individual examiners or in response to
supposed exigencies of the work where one division was thought to be
overloaded and another underloaded, and the alphabetical arrangement of
subclasses under each class has succeeded the alphabetical list of
names. The arbitrary correspondence originally established between the
alphabetical order of class titles and the numerical order was destroyed
as soon as expansion of the classification began.

However suitable to the then-existing material of the useful arts the
classification of 1872 may have been, it failed as fail all inductive
processes wherein the generalizations are not broad and deep. (Isaac
Newton's intellect could detect the resemblance between the falling
fruit and the motions of the planets.) The classification of 1872 was
not exhaustive; it failed to recognize to the fullest extent what Bishop
Wilkins saw nearly 300 years ago, to wit, that there are "arts of arts;"
and it failed to provide for future invention of new species in the same
art, and to recognize that new arts could be formed from combinations of
the old.


The Classification Division was created in the hope that guiding
principles of classification could be developed and applied for the
purpose of amending or revising the classification whereby patents could
be placed with greater assurance, and whereby the searcher with these
guiding principles in mind might find the nearest references. It was
confronted with the problem of revising while at the same time keeping
accurate record of all changes, correcting all indexes of patents, and
using copies in constant demand for search at the same time,
necessitating much clerical work, and constant interruption--of
correcting rather than planning anew; of mending a machine while
constantly increasing duty was required of it.

Ideas on the subject of revision were called for by the Commissioner of
Patents, and all in the Patent Office had an opportunity to set forth
their notions. The views of one met with approval and in accordance with
those views a "Plan of Classification" was prepared and promulgated in
1900. What other plans may have been submitted is not now generally
known. But in substantial accordance with that published plan, the
process of revision has proceeded for more than 14 years until
approximately 50 per cent of the patents (including incomplete work)
have been placed in revised classes.


No effective precedents have been found in any prior classifications of
the arts. The classifications of the principal foreign patent offices
have not been materially different in principle from the United States
Patent Office classifications of the past.

The divisions found suitable for book classification for library use,
have not been deemed adequate to the exactness and refinement essential
to a patent office classification of the useful arts. The systems of
class and subclass sign or number designations of the modern library
classifications, with their mnemonic significance, afford the most
important suggestions to be drawn from library classification. None of
these systems of designation has been adopted, (1) because of a serious
doubt as to the availability of such designations by reason of the
length or unwieldiness to which they would attain in the refinements of
division necessary in a patent office classification, and (2) because of
the enormous amount of labor necessary to make the change from present

The best analogies are in the known (but changing) classifications of
the natural sciences, and in them the problems are so different that
they can serve only to illustrate general principles. The broad
principles of classification are well understood. The authorities are
the logicians from the ancient Aristotle to the modern Bentham, Mill,
and Jevons. The effort of the Classification Division has been to adapt
and apply these well-known principles to the enormously diversified
useful arts, particularly as disclosed in patents and applications for


It may be well to insert here an authoritative definition: "A scientific
classification is a series of divisions so arranged as best to
facilitate the complete and separate study of the several groups which
are the result of the divisions as well as of the entire subject under
investigation." (Fowler, Inductive Logic.)

Investigation and study of any subject will be facilitated if the facts
or materials pertinent to that subject be so marshaled and arranged that
those most pertinent to it may appear to the mind in some form of
juxtaposition. It is the purpose of the Patent Office classification to
divide and arrange the body and multitudinous units of the useful arts
so that, having the question of novelty of any defined means to answer,
one may with reasonable assurance approach that portion of the rank of
arts in which it will be found if it is not new, and in propinquity to
which will also be found those means that bear the closest resemblances
to that sought for, the resemblances of other units growing less in
proportion to their distance therefrom.

Success in the fundamental aim of facilitating adequate search should
evidently at the same time reduce proportionately the danger that
interfering applications will be overlooked and also effect a
distribution of labor favorable to the acquisition of special skill.



A classification will be useful in proportion (1) to the pertinence to
the subject under investigation of the facts selected to be grouped
together, or, in other words, in proportion to the appropriateness of
the "basis of classification" to the subject in hand; (2) to the
convenience, stability, and uniformity of the arrangement of the
subdivisions whereby the investigator may proceed with reasonable
assurance to that portion of the rank of groups within which he will
find cognate material; (3) to the accuracy and perspicuity of the
definitions of the several divisions and subdivisions; (4) to the
completeness and reliability of the cross-referencing and
cross-notations; (5) to the uniformity, feasibility, and certainty of
the rules by which the accessions of patents disclosing one or several
inventions may be diagnosed and distributed to the appropriate divisions
of the classification in accordance with the basis adopted.

Corresponding to the foregoing analysis the theory of Patent Office
classification may be treated in five parts: (1) The principles on which
the arts shall be divided (basis of classification); (2) subdivision and
mechanical arrangement of groups; (3) definition; (4) cross-referencing
and search-notes; (5) the choice of features by which a patent shall be
assigned in the classification (diagnosis).


The first and most vital factor in any system of classification is the
basis of division, that is, the kind of characteristics common to any
number of objects selected to characterize groups, whereby the
individuals of any group will resemble each other for the purpose in
view more closely than any individual in any group will resemble any
individual in any other group.

"There is no property of objects which may not be taken, if we please,
as the foundation for a classification or mental grouping of those
objects, and in our first attempts we are likely to select for that
purpose properties which are simple, easily conceived, and perceptible
in a first view without any previous process of thought--but these
classifications are seldom much adapted to the ends of that
classification which is the subject of our present remarks." (J. S.
Mill, System of Logic.)

It is clear that a number of objects may be classified on several
different bases. For example, a number of books could be divided into
groups (1) according to the subject of their contents; (2) according to
the language in which the books are written; (3) according to the size
of page; (4) according to the binding material; or (5) according to the
color of the binding. Each of these may be useful classifications for
some purpose. For the student of literature none is of value except the
first; for the connoisseur in bindings, only the last three. A
classification of animals including classes of land animals and water
animals would hardly suit a student of zoology, as it would associate
with the shad and perch such differently organized creatures as the
porpoise, whale, and seal. Yet such a classification might prove very
suitable for a student of fisheries.

_Art as a basis._[1]--So in seeking a basis for a patent office
classification the purposes of the classification should be the guide.
Allegations of ulterior uses[2] (such as may be made merely because the
inventor thought of applying his invention to those uses only, or in an
effort to get the application examined in a certain division) and other
superficial bases should be avoided. That basis will best suit the
purpose which effects such an arrangement as will exhibit in suitable
groups the "state of the prior art," by which is here meant not
necessarily all the instruments of a trade or industry, or all the
articles sold by a shopkeeper, as a stationer, but those means that
achieve similar results by the application of similar natural laws[3] to
similar substances.

As all inventions are made with the ultimate object of satisfying some
human desire, the utility of an invention appears to be a natural basis
of classification. It is apparent, however, that most inventions may
contribute to numerous utilities besides the ultimate one. Many
processes and instruments intervene between the seed planter and the
wheaten rolls upon the breakfast table. The plow may be viewed as an
agricultural instrument or as an instrument of civil engineering,
according as it is used for preparing the field for planting or rounding
a road. A radiating coil of pipe may be thought of as a condenser of
steam or of alcoholic vapors, according as it is applied to one material
or another; as a cooler or a heater, according to the temperature of a
fluid circulated through it. A hammer may drive nails, forge iron, crack
stone or nuts. Underlying all of these ulterior utilities, there is a
fundamental one to which the normal mind will reach in its natural
processes and there rest. The plow loosens or turns over the surface of
earth; the coil effects an exchange of heat between its interior and
exterior; the hammer strikes a blow. A classification of plows in
agriculture, road building, or excavating, according to stated ultimate
use; of a radiator coil as a steam condenser, still, jacket-water
cooler, refrigerator, or house heater; of the hammer as a forging tool,
a nail driver, or a nut cracker, appears to separate things that are
essentially alike. But classifying a plow on its necessary function of
plowing, a radiator on its necessary function of exchanging heat, a
hammer on its necessary function of striking a blow, evidently results
in getting very similar things together. Assuming for the moment that
utility is a reasonable basis of division of the useful arts, it is
deemed more logical to adopt as a basis some utility that _must_ be
effected by the means under consideration when put to its normal use
rather than some utility that _may_ be effected under _some_ conditions.
Two of the five predictables of ancient logic are property[4] and
accident.[5] The capacity of the hammer to strike a blow, the capacity
of the radiator coil to exchange heat, are in the nature of properties.
The capacity of the hammer to crack nuts, of the coil to condense steam,
are in the nature of accidents--something that follows from the impact
and the heat exchange because of the particular accidental conditions of
operation. To select an accident as a basis of classification is
contrary to the laws of thought.

It may be said then that the Patent Office classification is based upon
"art" in the strict sense in which the word may be said to be used in
section 4886, Revised Statutes, but not necessarily in the looser sense
of industries and trades. A proper maintenance of the distinction
between the word "arts" of the statute and the phrase "industrial arts"
used in the sense of industries and trades is essential to an effective
classification for the purposes of a patent office search. Similar
instruments have been patented in three different classes, because of
the statements that one was designed for cooling water, another for
heating water, another for sterilizing milk; in four different classes,
because of the statements that one apparatus was to separate solids from
the gases discharged from a metallurgical furnace, another to separate
carbon from the combustion gases of a steam-boiler furnace, another to
remove dust and tar from combustible gas, and another to saturate water
with carbon dioxid. Owing to the continuance of a classification based
largely on remote use, many applications come into the office setting
forth inventions of very general application which nevertheless have to
be classified more or less arbitrarily in one of several arts in which
they may be used but to which they are not limited.

_Function or effect as a basis._[6]--Means of the useful arts are
related in different degrees. Resemblances selected as bonds for a
number of inventions may be more or less close. It is axiomatic that
close resemblances should be preferred over looser ones for
classification purposes. Processes and instruments for performing
general operations, such as moving, cutting, molding, heating, treating
liquids with gases, assembling, etc., are more closely bonded than those
for effecting the diverse separate successive operations directed toward
complex special results, such as making shoes, buttons, nails, etc.
Means of the former sort perform an essentially unitary act--the
application of a single force, the taking advantage of a single property
of matter. Those of the latter sort require the application of several
different acts employing frequently a plurality of forces or taking
advantage of several properties of matter. In the former case,
classification can be based on what has been called function, in the
latter it cannot be based on function but can be based on what has been
called effect (or product).

Function is closely related to cause. It is an axiom of logic that cause
is preferable to effect as a basis of those classifications designed for
scientific research. Hence the functional basis is preferred in all
cases in which it can be applied. A condenser for the fumes of zinc is
much more like a condenser for the fumes of acid or the vapor of water
than it is like the art of recovering zinc from its ores, and it employs
only one principle, to wit, heat interchange. A water-jacket for cooling
the walls of a gas-producer or glass-furnace is much more like a
water-jacket for cooling the walls of a limekiln or steam-boiler furnace
than it is like the art of gas-making or manufacture of glass articles.
In accordance with what are thought to be the correct principles,
therefore, the zinc-condenser ought not to be classified as a part of
the art of metallurgy, nor the water-jacket as a part of the art of
gas-making, merely because these instruments have a use in these arts,
but should be included, respectively, in classes based upon the more
fundamental utilities effected by them.

Although it is evident that molding a button is more like molding a
door-knob than it is like making buttons by the combined operations of
sawing, grinding, turning, and drilling, wherefore the molding of
buttons should be classified in a general plastic art rather than in a
special button-making art, yet the making of buttons by a plurality of
different kinds of operations can be placed only in a class based upon
the product, to wit, button-making. Since, therefore, the combination of
many different operations for the production of a specific article can
not be classified on the basis of any single function, it must be
classified on the basis of product. Thus by selecting essential function
as a basis when possible, and resulting effect when the functional basis
is not possible, one may approximate to the correct classification
described by Herbert Spencer as follows: "A true classification includes
in each class those objects that have more characteristics in common
with one another than any of them have with objects excluded from the

So it is deemed better to classify in accordance with the function or
effect it is known a means _must_ perform or accomplish than in
accordance with the _object_ with respect to which an act or acts are
directed or in accordance with some _effect_ which may or may not

_Structure as a basis._--The phrase "structural classification" is
frequently made use of. The application of the phrase to processes is
manifestly absurd. The Patent Office never had a structural
classification except in a limited sense. How could a machine, for
example, be classified on structure, leaving out of consideration its
function and the effect of its normal operation? In the refinements of
subdivision however, it becomes frequently desirable to form minor
subdivisions on structural differences. And it may also be that
instruments will be presented for classification that are of such
general utility as to baffle the efforts of the intellect to attain to
the fundamental and necessary function, in which case a
structure-defined class may best suit the needs of classification.

As between a classification based upon structure and one based upon
utility, the choice has been for the latter, without prejudice, however,
to instances that may arise in favor of the former.

The subject of structural classification will be dropped with a
quotation from the original pamphlet "Plan of Classification," etc. (p.
5): "A purely 'structural' classification is almost impossible on
account of the infinite variety of mechanical combinations, and to
attempt it would probably result in utter confusion, for the classes
could not be defined, and the classification would be a mere digest of
mechanical elements having no community of function."


Having divided the aggregate of things to be classified into a large
number of groups on a satisfactory basis, a most useful work will have
been accomplished and the purpose of a classification to assemble the
things most nearly alike and separate them from other things will have
been partially achieved. Unless these numerous groups are arranged in
some definite understandable relation to each other, or are placed in
definite known positions where they can be found, the mere formation of
the groups, on however good a basis, is not a complete classification.
Furthermore, unless the position of each group with respect to those
other groups that resemble it in whole or in part is made known, he who
wishes to find other related matter must seek aimlessly with no
assurance that his quest will end until the whole series shall have been
investigated. Each classified group is metaphorically a pigeonhole to
contain similar material. If the pigeonholes are properly labeled, one
can ultimately locate those that contain the matter he is seeking if he
knows the name that has been applied to it. If the pigeonholes are
arranged in alphabetical order, for example, he may find all related
material, _provided he knows the name of every related group of
material_, even though very similar things may bear names as far apart
as A and Z. But if all things were so placed that, adjacent and in
certain fixed relation to each pigeonhole, other related matter could be
found, the resemblances lessening in proportion to the separation, and
if the entire area of pigeonholes were divided, and certain areas
assigned to certain kinds of things defined in general terms, guessing
the location of and desultory search for things that may have different
names, but yet be very much alike, would be lessened and all cognate
material be bunched. A second vital factor of a system of
classification, therefore, is the arrangement of the groups.

_Infinitude of possible combinations._--There are now over 1,125,000
United States patents, each presumptively covering a creation of the
useful arts that is different from every other. Most of these patents
also disclose a plurality of elements or acts. Each of these patented
means is potentially an element of a more complex combination that may
be patented. When one considers merely the number of forms of energy,
the number of known substances and known mechanical elements, and
attempts to figure possible combinations and permutations, it becomes
apparent that the size of the numbers resulting is incomprehensible.
Consider the possibilities of combination also of the enormously varied
disclosures of patents. Calculations of the possible combinations and
permutations of a small number of objects are familiar. Different
combinations of the letters of the alphabet are sufficient to record the
sum of human knowledge in many languages. With substantially two octaves
of the diatonic scale the world's melodies have been sounded, nor do any
doubt that our successors will thrill to airs that we have never heard.
"Thirty metals may be combined into 435 binary alloys, 4,060 ternary
alloys, 27,405 quaternary alloys" (Jevons). This does not take into
consideration differences in proportion that figure so largely in
results in the arts of substance-making. The total number of possible
alloys of the known metals is incomprehensible. A moment's thought
respecting the numbers of the means of the useful arts will alleviate
any fears that the possibilities of invention are near the limit and
will give food for further thought to all concerned with this attempt to
classify the useful arts to the point of refinement necessary to enable
this office to pass judgment with reasonable speed and accuracy upon the
approximately 75,000 applications filed each year.

_Division and arrangement in the natural sciences._--Some of the natural
sciences are said to be in what is known as the classificatory stage of
development. In some sciences the subject of classification has been
predominant and these furnish excellent examples of scientific

The much-admired classifications of zoology, botany, and mineralogy are
among the best available models of logical division,[8] systematic and
analytical arrangement. The most casual consideration of these
classifications, however, renders apparent the relative simplicity of
the task of classifying natural objects differentiated by fixed natural
laws as compared with the task of classifying the products of the
creative and imaginative faculties as applied to the useful arts. The
chimera and other animal monsters occur only as figments of the mind.
Zoological classification does not have to classify combinations of
birds, fishes, reptiles, and mammals, nor does it deal in the way of
classification with the parts of animals, nor is the question of
absolute numbers of instances a matter of moment to such a
classification, all of the members of a species being alike for
classification purposes. But any instrument of the useful arts may be
combined with some other, any part with some other part. Organizations
may be parts of some other organizations, or even mutually parts of each
other, as, for example, a pump may be a part of a lubricator, or a
lubricator may be a part of a pump. Some parts are peculiar to one
instrument, some are common to many. Every member of a species differs
from every other member. Added to this, the intellectual differences
between the persons who present the applications for patent, the
differences in their generalizing powers, the relatively broad and
narrow views of two or more persons presenting the same invention
(variations not indulged in by nature) complicate the problem of
classifying the useful arts.

_Difficulty of entitling a subclass corresponding to every
combination._--In any main class or group of the useful arts there are
always a number of characteristics that it may be desirable to take note
of in subdivision titles. A moment's thought shows the impossibility of
taking care of any large number of combined characteristics so as to
provide exactly for each combination, for the reason that the
limitations of space and of the perceptive faculties forbid. For a
simple illustration, the imaginary classification of books for use by a
bookseller may be recurred to. The dealer, it may be assumed, has books
on (1) four different subjects, history, science, art, and fiction, (2)
each printed in four languages, English, German, French, Spanish, (3) in
four different sizes of page, folio, quarto, octavo, duodecimo, (4)
bound in four materials, leather, rawhide, cloth, paper. Here are four
main characteristics, each in four varieties. A customer is likely to
ask for Ivanhoe in English, octavo, bound in leather. Now if the
bookseller had sought to arrange the books into one class according to
subject matter, into another according to language, another according to
size, another according to binding, he would have fallen into confusion,
because his classes would be formed on different principles or bases and
overlap. Some histories will be in French, some will have octavo pages,
and some cloth bindings. But if he divides first on the basis of subject
matter, then each subject matter into language, each language book into
sizes, each size into material of binding, he can immediately place his
hand on a class wherein the book will be if he has it; but this
classification, based on four different characteristics and four
varieties of each, has necessitated the formation of 256 classes or
divisions, and if five characteristics were provided for, 1,024
divisions would be required.

Adapting the illustration of the books to a patent office
classification: If it were possible to view these characteristics as
patentable in combinations of all or in any combinations less than all,
and also as separate characteristics, 16 divisions additional to the 256
for each independent characteristic would have to be provided, as well
as other divisions for combinations of less than the whole, in order to
make the classification absolutely indicative of every feature, and the
number of divisions would be enormous. In such a classification, after
the proper division had been located, the search would be nothing, the
difficulty would be to find the appropriate class.

_Expedients to reduce the number of subdivisions._--Fortunately most
people carry on their mental processes in accordance with certain
uniformities. Under this uniformity of thought no patentable
relationship may be alleged between a quarto volume and the subject of
history or between a leather binding and the German language; wherefore
4 classes of coordinate value, based on the 4 characteristics, each
divided into 4 subclasses, 16 divisions in all, may serve the purpose of
a Patent Office search. But if, as sometimes happens, a patentable
relationship had been assumed and admitted between a leather binding and
any of the languages, or any of the subjects, or between any two or more
of those different characteristics, provision could be made for such
combinations by the following expedients:

(1) Arrange the characteristics, in the order of relative significance
or importance for the purpose in view, in four groups, giving each group
the characteristic title. Under each title arrange the varieties in a
similar relation as follows in either (1) or (2):

             (1)                             (2)
         Cl. X.--BOOKS.                 Cl. X.--BOOKS.

 0.  Miscellaneous.                 1. Subject-matter--
 0.5 Subject-matter--               2.   History.
       1. History.                  3.   Science.
       2. Science.                  4.   Art.
       3. Art.                      5.   Fiction.
       4. Fiction--                 6. Language--
 4.5 Language--                     7.   English.
       5. English.                  8.   German.
       6. German.                   9.   French.
       7. French.                  10.   Spanish.
       8. Spanish.                 11. Size--
 8.5 Size--                        12.   Folio.
       9. Folio.                   13.   Quarto.
      10. Quarto.                  14.   Octavo.
      11. Octavo.                  15.   Duodecimo.
      12. Duodecimo.               16. Binding--
 12.5 Binding material--           17.   Leather.
      13. Leather.                 18.   Rawhide.
      14. Rawhide.                 19.   Cloth.
      15. Cloth.                   20.   Paper.
      16. Paper.

Subject-matter, assumed to be the most important characteristic, is
placed first. Any exhibit of mere material for binding, mere size, mere
language, or mere subject-matter, would fall into the correspondingly
entitled group. If, however, a book on history in German or a history in
red leather, etc., were to be classified, it would be placed in subclass
"History" in the subject-matter group, and a French book in green cloth
would be placed in subclass "French" in the language group. That is,
combinations of any characteristic with any one or more other
characteristics may be placed in the group for that characteristic
deemed the most significant and which is highest in the schedule. Again,
by assigning a number to each generic title, each such title becomes
thereby the miscellaneous group for varieties other than those indented
under it, as well as for all varieties associating any characteristic
with one or more of those standing lower down. Thus, a book of poems
would belong in subclass "Subject-matter" and a 16mo volume bound with
purple celluloid covers would belong in subclass "Size." So, by giving
meaning to relative position, exhaustive arrangement is sought to be
provided in a reasonable number of groups. To provide for other features
that may be presented in future, an additional miscellaneous group may
be added at the top (1), or the class title (2) might be deemed to
represent the unclassified residue and a depository for future matter
not specifically provided for.

(2) If the number of instances of association of subject-matter and
binding materials, language and size, etc., are numerous, additional
groups might be placed above the groups having the names of the
characteristics, the fact of the existence of these groups indicating
that the characteristic groups are for single characteristics only and
do not include books having several different ones. In such case the
schedule might be headed by a miscellaneous group, having either the
title "Miscellaneous" or the title of the class, to receive associated
characteristics not provided for by specific titles, immediately
followed by subclasses for the particular associations found to be most
numerous, as follows:


 Subject-matter and language.
 Subject-matter and binding material.
 Binding material.

To illustrate further, selecting for the purpose a mass of objects
presenting problems more nearly like those presented to the office in
questions of patentability, let it be assumed that one is to classify
the objects in a heap of metal scrap.

On looking over the material of the heap it is noticed that there are a
large number of metal balls; some have holes through them, some are
hollow, some are smooth on the outside, and some are hollow, smooth, and
perforated, but they are all nevertheless balls, and accordingly all
balls can be separated out and placed in a heap by themselves. Next, the
presence of bars in the general mass is observed, some long, some short,
some straight, some twisted, some of round stock, some of square stock,
etc. These may be gathered together and placed in a separate pile at the
left of the balls. It is further observed that there are many
differently shaped annular bodies in the heap resembling generally the
single links of a chain, some circular, some elliptical, some twisted,
some made of round stock, some of square stock, etc. They are all
nevertheless annular bodies; these may be placed in a separate pile at
the left of the bars.

Now, in the remnant of the original heap, a sufficient number of similar
single elements does not remain from which to make a smaller pile of
elements. Different combinations of links, balls, and bars are, however,
observed in the remaining heap. Some are combinations of links, some
combinations of a ball and link, some of a bar and link, and some of a
bar, link, and ball. These different combinations may be separated out
in the order named and placed in separate piles. After all these things
have been removed, there is left in the original heap a number of odds
and ends or miscellaneous metal objects.

These several groups may now be arranged in the inverse order in which
(in the particular illustration adopted) they have been removed, thus:

 1. Miscellaneous (remnants of the original heap of scrap).
 2. Combined bar, link, and ball.
 3. Combined bar and link.
 4. Combined bar and ball.
 5. Combined link and ball.
 6. Chains.
 7. Links.
 8. Bars.
 9. Balls.

Knowing that objects of metal scrap not covered by the specific titles
will be found in the miscellaneous group, and that the more complex
specifically-named things are to be found first after the miscellaneous
or at the left of the row of piles of materials thus separated and
arranged, and the more simple things and parts farther to the right, the
particular piles to resort to for the things wanted may be definitely
determined. The same processes may be applied to each of the piles.
Thus, balls, in the above illustration, may be divided into--


  10. Hollow perforated.
  11. Hollow grooved.
  12. Hollow.
  13. Perforated.
  14. Grooved.

Again, the same processes may be applied to a mass of more diversified
junk, of which the metal scrap may form one pile, rags another, old
bricks another, old timber another, and, still another, timber having
metal-straps, bolts, nails, etc., connected with it.

_Superiority and inferiority._--In the arrangement of subclasses in a
class, those groups that are related to each other as wholes and parts
are arranged so that the wholes shall stand before the parts, and so
that subclasses defined by effect or by special use shall stand before
those defined by function or general use. For example, in the scrap
illustration above, assuming the titles to be in a printed arrangement,
"chains" precedes "links," which may be parts of chains, and if it had
been desired to separate animal-drags, for instance, from the scrap,
some animal-drags being particular adaptations of a bar, links, and
ball, the group of animal-drags should precede "Bar, link, and ball."
The words "superior" and "inferior" have been used to indicate this
relationship. A class or subclass defined to receive a certain
combination is superior to one defined to receive an element or a
combination that is a part of that certain combination. A class or
subclass defined to receive means for making a particular product, as an
electric lamp, is superior to a class or subclass designed to perform a
general function, as pumping air from a container. And whenever a
question of assignment of a patent or application that contains matters
of two or more groups bearing that relation is raised, the "superior"
group is selected to receive it.

Further, in those instances in which groups are formed on different
bases or different characteristics, not comparable with each other, and
a patent is presented having matter falling in each group, that group
which is highest in position is preferred in those instances where
separate provision for means having both characteristics has not been

In cases of necessity, as where a combination is presented for which no
class has been definitely provided, but classes exist into which the
several parts would fall if separately claimed, the same practice that
obtains in similar situations with respect to two or more _subclasses_
of a class may be followed with respect to two or more _classes_ and the
patent placed in that class which, in accordance with above-stated
principles, should be deemed the "superior."

_Definite positional relationship of subdivisions._--In the metal scrap
example, above, division has been effected on the one basis of form or
contour. If it had been desired to separate also on material, for
example, if it were deemed important to locate all brass scrap, each of
the groups based upon form could be divided into one of _brass_ and one
_not brass_, or the entire heap could be divided into _brass_ and _not
brass_, and under the heading "brass" could be indented the various
articles made of brass, and under "not brass" the various articles not
made of brass, and this would double the number of divisions. If also it
were desired to separate the lead articles in the same manner the number
of classes would be tripled. But, as in the book illustration, it may be
impracticable thus to multiply subdivisions, and the basis "form" having
been selected as of _first-rank_ importance, all divisions based upon
form should be completed and kept together. Then, "material," having
been selected as of _second-rank_ importance, should be carried out with
respect to all objects in which form is non-essential. If enough brass
balls were found to render it advisable to make a subdivision of them,
they should be assembled into a subclass indented under "balls" and not
into a subclass indented under "brass." Having selected one basis as
_primary_, it should never subsequently be made _secondary_ or _vice
versa_. Some such restriction on modes of division appears salutary in a
system of divisions designed to definitely limit search. The arrangement
herein sought to be explained is susceptible of use to limit all
searches for a single definitely stated invention to a subclass properly
entitled to receive it or those indented under it, and to those
subclasses above, which may include it as a part of an organization or
specialized means.

As between coordinate groups divided on the same basis, there is no
question of superiority and inferiority. The terms "superior" and
"inferior" are useful in questions of relationship between combinations
and subcombinations or elements thereof, and between groups founded on
effect or product and those founded on simple function. The mere
difference in complexity of mutually exclusive coordinate groups
involves no relationship of superiority or inferiority. A subclass to
receive a screw-cutting lathe is superior to a subclass to receive a
lathe-headstock, a locomotive class is superior to a class to receive
steam-engines, for the reason that the lathe is a whole of which the
headstock is a part, and the locomotive is an organization of which the
engine is an element. But the headstock subclass is not superior
necessarily to the tailstock subclass simply because the headstock is
commonly more complex than the tailstock. Yet arbitrary preference for
classification in the headstock subclass may be established by position
where an application or a patent contains claims for both.

Thus in a class that is founded on a well-chosen basis that brings
together things bearing close resemblances to each other, all types that
contain the elements essential to produce a complete practically
operative means will be found in subclasses that have a position
somewhere between the beginning and end of the list of subclasses of the
class. Those that add features of elaboration of the essential types and
those that are highly specialized to some particular purpose within the
definition of the class will stand above the essential type subclasses,
while those subclasses for parts and details will stand below those for
the essential types.

_Indented schedules._--In an indented schedule all subclasses in the
first column reading from the left are species to the genus represented
by the class title.[9] All subclasses indented under another subclass
are species to the genus represented by the subclass under which they
are indented. If a title has no number, it represents merely a
subject-matter to be divided, a genus,--having no representatives except
in the species under it. If a subclass having a generic title has a
number, it not only represents a subject-matter to be divided into
species but also all other species not falling within the titles
indented. Although these relative positions might imply that only
proximate species are indented one place, yet mechanical difficulties
render it impracticable to so arrange that all species shall be indented
under their proximate genera.

Indention properly carried out has a tendency to prevent in the process
of logical division the logical fault of proceeding from a high or broad
genus to a low or narrow species. This latter fault may inadvertently
separate things that belong together. If, for example, it were desired
to divide balls in the stated illustration according to material, an
immediate division of balls into aluminum, zinc, glass, ivory, rubber,
would be less useful than to divide into mineral materials and
nonmineral materials as follows:


However, it is evident that indention carried to its full extant, useful
as it is in keeping analogous things together, would make the printing
of schedules complex and unwieldy. Nevertheless, in the generalizing
process necessary in logical division and arrangement, the divisions of
species should always be _mentally indented_, as it were, under their
_proximate_ genera. Thus, under a genus unnamed may be arranged several
species in juxtaposition, without actually printing the name of the
genus, so that the schedule above may read:


In an arrangement printed in idea-order, though relegating the genera
mineral, nonmetallic, metallic, nonmineral, vegetable, animal, to the
mind unaided by printed words, the different species of the same genus
may be kept together except that species for which no title has been
provided must go back to the subclass under which the named species are
indented. Thus the arrangement above necessitates placing in subdivision
"Balls" all _copper_ balls, whereas indention under proximate genus
"metal" would have brought all metal balls together. In a finely divided
classification, printing of titles for all genera is not practicable;
hence great care ought to be directed toward grouping species according
to the principles of arrangement herein outlined, noting that whenever a
change of basis is made, a new genus is implied, and that subclasses for
all other species of the same genus under whatever name, must be brought
into juxtaposition as if indented under the implied genus.[10]

_Bifurcate division._--Most discussions of classification make reference
to the so-called bifurcate scheme of division as the only one by which
exhaustive division can be surely achieved. This is commonly illustrated
by the ancient tree of Porphyry. By this method any subject it is
desired to subdivide is first divided by writing the name of one
selected species at one branch and writing at the other branch the name
of the same species prefixed by "Not." Thus the Agassiz classification
of living beings divides them first into sensible and not sensible
(plants). A botanical classification divides plants into flowering and
not flowering. A zoological classification divides animals into
vertebrate and not vertebrate. By continuing the process of division in
the same manner, the division is obviously exhaustive of the subject,
there being always a negative subdivision to receive any subsequently
created or discovered species. Although bifurcate division has been
ridiculed by some, it is agreed by highest authority that it is the only
plan of division by which one can be sure to have a consistent place for
everything, or by which one can be certain that the divisions are
mutually exclusive. It can be demonstrated that a classification
schedule in which the relation of genera and species is shown by
indentions, if correctly formed on the principles now sought to be
applied in the revision of the Patent Office classification, is
susceptible of conversion into a tree of Porphyry, while unlike the
latter it is compact and wieldy.

_Utility of arrangement according to resemblances._--The expedient of
indicating kinds of relationship between several equally indented
divisions by relative position has the following utility:

(1) A uniform rule is provided, applicable to all classes, for placing
inventions that bear the relation of whole to part in subdivisions
before those that bear the relation of a part to that whole, and those
that are defined by a particular effect, product, material, or use
before those that are defined by a function or an operation applicable
generally to various effects, products, materials, or uses; whereby that
portion of the schedule in which any invention belonging to any
particular class should be found may be approached whether or not the
investigator knows the name of the object sought for or the title of the
appropriate subdivision.

(2) The substantial impossibility of dividing many branches of the
useful arts exhaustively into a reasonable number of mutually exclusive
or non-overlapping subclasses is compensated for; so that when the
classifier or the searcher has an invention to place or to find
including two or more different kinds of characteristics, for each of
which a subdivision is provided, but no subdivision for the plural
characteristics, it will be known that the invention should be in the
subclass for that characteristic which stands before the subclass for
the other characteristic.

(3) It compensates for omission of some generic titles that if written
in the indented schedule would lengthen specific titles to a cumbersome

(4) It provides a rule for cross-referencing where several inventions
are claimed bearing to each other any of the relationships indicated
above, cross-referencing being necessary in one direction only where the
matter illustrated is coextensive with the matter claimed.

(5) It definitely limits the field of search for any _unitary invention_
in any class so arranged, as no patented invention having the
limitations imposed by a unitary claim should be found in any subclass
below the subclass properly defined to receive it or those indented
under it. Parts of such inventions may be found below or following this
subclass in the same class if these parts are within the class
definition, or elsewhere in the useful arts if not within that
definition. The unitary invention may be found in the subclass limited
to it and certain subclasses arranged _above_ or _before_ it adapted to
receive organizations of which it may be a part.

A complete system of arrangement should comprise (1) a display of the
entire field of the useful arts in a manner to show the relation of the
larger as well as of the smaller groups,--carrying the appropriate
relationship as far as possible from the highest genera to the lowest
species, the arrangement being such as would bring materials most nearly
alike into closest propinquity regardless of the names they may be
called by. (2) Supplementary to this classification arrangement by ideas
there should be an alphabetical index of subclass titles, appropriately
cross indexed, and additional titles of various technical and trade
names of things classified under subclass titles.


Definition is indispensable in any classification and is very
difficult. Every class must be defined and all of the groups under it.
After definitions have been made and printed, they are sometimes found
inadequate and must be supplemented by the definitions of other classes.
This is unavoidable while the complete material remains unexplored.
Definition in the strict logical sense is not to be expected, nor is it
necessary. It is commonly sufficient if an explanation or comparison be
made sufficient to direct the mind to the character of the contents of
the group and indicate its limitations. Hitherto four of the five
predicables of ancient logic have been mentioned, to wit, genus,
species, property, and accident. In connection with definition, the
fifth predicable, difference, is useful. To define a class, it is
sufficient, generally, for the purposes of office classification, to
state a _peculiar property_ (not an accident) of the objects included in
the class; and to define a species under the class it is sufficient to
state the name of the class plus the difference--i. e., with the
addition of the limitations that characterize the species.[11] This
procedure in definition is susceptible of application from the highest
genus to the lowest species. It is advisable to define the means
included within a title without any introductory words, such as "this
subclass includes inventions relating to," etc., treating the subclass
for definition purposes as if it were a collection of concrete things,
in the same manner as in a dictionary definition.


If patents were in all respects like material objects, cross-references
and search-notes would not be necessary. Nails, screws, locks, hinges,
and boxes are distinct things susceptible of definite separation and
classification. Even though nails, screws, locks, and hinges form part
of the box, the box is still a box, not a nail, screw, hinge, or lock.
For the needs of the Patent Office classification, however, although a
patent for a box must be classified with boxes, yet if a peculiar nail,
screw, lock, or hinge is claimed in the same patent with the box, or
even if any one of these customary accessories of boxes is illustrated,
it may be necessary to provide copies of the patent for the box in each
of the several classes provided for nails, screws, locks, or hinges.

Inasmuch as every relatively complex thing is made up of relatively
simple things, it is obvious that all disclosures can not be
cross-referenced. Any attempt to calculate the number of
cross-references to be supplied if all disclosures of the subjects of
invention were to be cross-referenced would show the number to be
incalculable. It is necessary, therefore, to leave to the judgment of
the classifier the propriety of cross-referencing unclaimed disclosures.

Should a patent contain a number of claims defining a number of
differently classifiable inventions, complete cross-referencing from the
class in which the classification is made original into the other
appropriate classes or subclasses should be effected, _unless_
cross-search notes or arrangement of subclasses with appropriate titles
may be substituted to advantage.

Cross-referencing or cross-search notes are made, as a rule, from
combination class to element class, but never or very rarely from the
element class to the combination class in which it may be used. Thus
cross-referencing should normally be downward in a schedule of
subclasses. Search notes indicate parallel or otherwise related classes
and subclasses, and those classes and subclasses in which analogous
structures having different purposes but adapted to answer broad claims
may be found.

By arbitrary rules of arrangement such as have been referred to in the
section dealing with division and arrangement, a search may ordinarily
be definitely limited to a certain number of subclasses, even where
cross-references are not made. In such arrangement any given patent, _if
it be directed to one invention_, may be searched in the subclass within
which the definition places it or subclasses indented under it, and in
certain subclasses above, whose titles will indicate that the invention
might be included as a part of the matter defined to belong therein, but
it would never have to be searched in any subclass following and not
indented thereunder.


Each patent and each application discloses one or more means of the
useful arts (using the term "means" to cover both processes and
instruments in the sense in which it is used by Prof. Robinson), almost
always more than one, since most new means are combinations of
mechanical elements or acts. In some patents and applications the
disclosure is coextensive with that which is claimed; in others there is
matter disclosed but not claimed. The unclaimed disclosure may be as
valuable as the claimed disclosure for purposes of anticipation, and the
classification must provide for both. If the claimed disclosure belongs
in one class and the unclaimed in others, the classifier must choose
between two or more classes that one in which the patent or application
shall be classified and those into which it shall be cross-referenced.

_Claimed or unclaimed disclosure._--The claims of a patent are the
statutory indices of that which the applicant believes to be new, they
define an invention that has been searched by the Patent Office and no
anticipation discovered for it. Future action must be based on
inductions from past experience; none knows what the future lines of
search will be; the only guides for future searches are the searches of
the past; the evidence of past searches is the claims of patents; they
trace the course of invention. Furthermore, a presumption of novelty
attaches to the claimed matter; no such presumption attaches to the
unclaimed. The law requires every patent for improvement to show so much
of the old as is necessary to explain the uses of the improvement. In
practice much more than that is disclosed. Questions as to the proper
placing of patents and cross-references would be diminished by the
strict enforcement of Rule 36 of the Rules of Practice requiring that
the description and the drawings, as well as the claims, be confined to
the specific improvement and such parts as necessarily coöperate with
it. In any event both the claimed disclosure and that which is unclaimed
must be taken care of, one by cross-reference, and the disclosure
selected for cross-reference is that to which no presumption of novelty

This practice of placing patents by the claimed disclosure is sometimes
misunderstood. Its chief application is in determining classification in
case of disclosures involving a plurality of main classes. Furthermore,
the mere letter of the rule is not to be applied in preference to its
spirit. Subcombinations claimed may be placed with the combinations, and
in subordinate type subclasses patents must be placed sometimes by
claimed and sometimes by not-claimed disclosures.

_Diagnosis of pending applications._--What has been said relates to
patents. The bearing of the practice of adopting the claimed disclosure
as the basis of assignment of applications for examination has also to
be considered.

Two pending applications claiming the same means very commonly differ
in the kind and extent of disclosure. One application may disclose
several inventions. Which of the several disclosures shall be selected
as the mark by which to place the application? For instance, the typical
wire-nail machine has a wire-feeding mechanism, a shearing mechanism, an
upsetting (forging) mechanism, side-serrating mechanism, and pointing
mechanism; it may also have a counting mechanism, a packaging mechanism,
an electric motor on its frame for furnishing power; and, in addition,
numerous power-transmitting and other machine parts, such as bearings,
oil-cups, safety appliances, etc. The applicant may have made a complete
new organization of nail-machine and may seek a patent for the total
combination. He may have invented a new shearing mechanism and have
chosen to show it thus elaborately in the place of use he had in mind,
or he may have designed a new counter or a new oil-cup or a new power
transmission, or even a new motor, and have given his invention this
elaborate setting. The shears, the counter, the oil-cup, the power
transmission, and the motor are separately classifiable in widely
separated classes. How shall the application be diagnosed for
determining its place in the office classification? When the
specification and drawing disclose (as most of them do) several subjects
matter of invention, though claiming only one, which of those several
subjects matter shall control the classification?

The most natural procedure, at first thought, would be to classify on
the totality of the showing, in which case the application for the
nail-machine, supposed above, would be assigned to nail-making. But
imagine the invention claimed by an applicant to be the counter. Then
the examiner in charge of nail-making would have to search the class of
registers with which he is not familiar. Suppose applicant No. 2 files
an application for the same counter which he illustrates and describes
in connection with a bottle-filling machine, and that, classifying on
the totality of the showing, this goes to the division that has the
class of packaging liquids. Now both the examiners in charge of
bottle-filling and nail-making, knowing that counters are classified in
registers, search the class of registers and also the pending
applications in registers. After these examiners have made their
searches, suppose applicant No. 3 files an application for the same
counter, which he says may be used for counting small articles produced
by automatic machines. Perhaps he shows the counter attached to a piece
of conventional mechanism representing any manufacturing machine,
mentioning, say, a cigarette or pill or cartridge-making machine. It has
not occurred to either the the examiner of nail-making or the examiner
of bottle-filling that the other might have any such application; nor
does it occur to the examiner in charge of registers to search
nail-making or bottle-filling. As the specification of the counter
application mentions cigarette, pill, and cartridge-making machines to
which the counter may be attached, the examiner in charge of registers
may search those classes. Suppose that the counter proves to be new, and
each of the three examiners allows a patent. Here now are three patents
for the same thing. Of course, after allowance, the counter and all
other disclosed inventions that give any suggestion of novelty are
cross-referenced; but the primary purpose of a patent office
classification (to aid in determining patentability) has failed in this

In the imagined situation respecting pending applications, without doubt
diagnosis and classification upon the invention claimed is necessary to
effect the purpose of the office classification. Cross-referencing after
issue can not undo that which has been done.

If no application save that of the nail-machine be pending, no
duplication of patents occurs, but the labor of search is increased by
reason of the unfamiliarity of the examiner with the inventions he has
to search. After the patent is allowed he may find the entire
combination of the nail-machine without the counter disclosed in a
patent for a nail-making machine, so that as a nail-making machine this
new patent is of no value as a reference. Very probably all of the other
inventions illustrated (except the counter) are also old in their
respective classes; but the examiner of nail-making can not tell this
without extensive searches in those classes, so he notes
cross-references for them all.

_Difficulties due to varying ideas of claims._--Very troublesome
questions are constantly arising as to whether an invention should be
classified in a combination class or an element class. The point will be
illustrated by example: A describes and illustrates an automobile having
an internal-combustion motor and a friction-clutch in the motor
transmission-gear. He states that the clutch is in the usual
relationship to the motor and gearing, but claims a new clutch for
whatever it may be adapted. B discloses an internal-combustion motor
said to be for automobiles with transmission-gearing and a
friction-clutch and claims "in an internal-combustion motor a
friction-clutch," etc., specifying the form of the clutch. C makes the
same disclosure, but claims "an internal-combustion motor having a
specified clutch," while D, with the same disclosure, claims "the
combination with the internal-combustion engine of an automobile" of a
specified friction-clutch. E claims and illustrates only the
friction-clutch. Should these be classified together? If so, in what
class? Should a bearing composed of a specified alloy of copper, tin,
and antimony, be classed as a bearing or as an alloy? Should a house
painted with a mixture of linseed oil, lead oxid, and barium sulphate go
to buildings or coating compositions? A lamp-filament of titanium and
zirconium with electric lamps or with alloys? A building-block of
cement, lime, sand, and carborundum, with building-blocks or plastic
compositions? Whether these be diagnosed as combinations or as elements
and compositions respectively, and classified accordingly, criticism
will be aroused. The point in view is that although principles of
patentability must be considered in a classification designed as an
instrument to aid in determining patentability, convenience and accuracy
of search and avoidance of voluminous cross-referencing may necessitate
some arbitrary rule of classification to meet various and changing
theories applied to the drafting and allowance of claims.

From the foregoing it will be evident that classification involves
orderly logical processes of induction (supplemented by hypothesis), of
definition and of deduction. After gathering a large number of facts
generalizations are made from them and a hypothesis is found to be
confirmed or modified by more extended research; the divisions are then
defined; by correct diagnosis of other instances (as other patents)
deductions may be drawn respecting the appropriate place for them in the

[1] An "art," in the sense of a single unitary invention, is a synonym
of process, method, and operation. The term "art" is ambiguous in
popular usage. In the phrase "useful arts" in the Constitution, it
denotes the area of endeavor to which the patent laws apply. When the
word "art" is used to specify some fragment of the useful arts, it
commonly raises different notions in different minds. It may be
correctly used to designate _any_ division of the useful arts. It is as
proper to speak of the art of grinding or the art of molding as of the
art of metal-working or the art of brickmaking.

[2] A "use" is an application of a means to substance to produce an
effect which may or may not be the necessary effect of the means in its
normal operation. A catalytic may be used to ignite gas or to convert
oleins into stearines. An ice pick may be used to hold a chalk line or
prick holes in leather, etc.

[3] By "natural law" in the useful arts is meant that uniformity of
action which is manifested whenever any particular substance in any
particular condition is brought into such relation with any particular
manifestation of energy that the force exerted modifies or prevents
modification of the form, nature, condition, or locus of the substance
or modifies the manifestation of energy or both.

[4] A "property" may be described as any quality common and essential to
the whole of a class but not necessary to mark out that class from other
classes. Thus, all wheel tires may be said to possess annularity; but
washers and finger rings are also annular. A "peculiar property" is one
that not only always belongs to a class of objects but belongs to that
class alone; thus a circle has the peculiar property of containing the
greatest space within a line of given length, and catalytic substances
have the power of setting up chemical reaction without themselves being

[5] An "accident" is any quality that may indifferently belong or not
belong to a class without affecting the other qualities of the class.
That a man's name is James is an accident telling nothing of the man's
physique or character.

[6] "Effect" or "result" is the consequence of a process of the useful
arts practiced with or without instruments. The effect of an instrument
is the effect of its operation. Effects may be direct or indirect,
proximate or remote, necessary or accidental.

"Product" is an effect consequent upon a process that changes the form,
state, or ingredients of matter perceptibly and permanently, as
distinguished from effects that are fleeting or involve no change in
perceptible form, state, or ingredients of matter.

"Function" is the "action of means upon an object while producing the
effect." (Robinson.) Functions may be direct or indirect, proximate or
remote, necessary or accidental. The direct, proximate, or necessary
function of the hammer in normal operation is impacting. Indirect,
remote, or accidental functions of a hammer may be comminuting, forging,
driving, etc.

[7] Classification of the Sciences.

[8] Logical division is the process by which the species of which a
genus is composed are distinguished and set apart. Physical division or
partition is the process by which the parts of any object are
distinguished and set apart. Metaphysical division is the process by
which the qualities of a thing are segregated and set apart in thought.

[9] Any class of objects may be called a "genus" if it be regarded as
made up of two or more different kinds of objects or of two or more
species. "Motors" is a genus when the class "Motors" is considered as
divided into electric motors and nonelectric motors, or electric motors,
spring motors, weight motors, current motors fluid pressure motors, etc.
A genus is more extensive than any of its species but less intensive.

A "species" is any class that is regarded as forming a part of the next
larger class, "electric motors" being a species of "motors" and "motors"
being a species of "energy transformers." A species is more intensive
than the genus to which it belongs but less extensive.

Every species may be a genus to another species until no further
subdivisions can be made. This last indivisible species is termed the
_infima species_. Every genus may be a species to another genus until a
point is reached where no further generalization may be made or the
_summum genus_ is attained. In the Patent Office classification of the
useful arts, the _summum genus_ is useful arts. The _summum genus_ of
the plastic arts would be plastics. The _infima species_ in the useful
arts evidently never can be attained.

"Proximate species" and "proximate genus" indicate, respectively, those
species that are divided from a genus without intermediate genera, and
those genera from which the species are directly divided. Motors, and
not energy transformers, is the proximate genus to the species, fluid
motors, electric motors, etc., while fluid motors, electric motors,
etc., and not steam engines, alternating current motors, etc., are
proximate species to motors.

[10] In the Manual of Classification of the U. S. Patent Office the
arrangement of subclasses has always been alphabetical, although in the
Supplement containing definitions of revised classes the arrangement is
numerical. If the latter schedule of "Balls" in the text had been
printed in alphabetical order, it is apparent that the species
"Aluminum" and "Zinc" of the genus Metal would be as widely separated as
possible. In the former schedule of "Balls," in which the genus Metal is
printed, "Aluminum" and "Zinc" come together. It is apparent that in an
alphabetical arrangement allied species can not be kept together without
printing every proximate genus. This fact, among others, indicates the
advisability of abandoning the alphabetical arrangement in the
classification manual and adopting the idea arrangement in the schedules
of revised classes, supplemented by a consolidated alphabetical index of
all subclasses.

[11] A species contains all the qualities of the genus and more. These
additional qualities form the "difference." The electric motor has the
qualities that are common to motors and is differentiated by reason of
the fact that electric energy is thereby converted to mechanical motion.

[12] Classification of a patent is said to be "original" in the class
and subclass which receives the most intensive claimed disclosure, and
in which the patent is indexed in the official classification indexes.
"Original classification" is referred to as opposed to "classification
by cross-reference."

A "cross-reference" is a copy of a patent placed in a subclass other
than that in which the classification is made original, in order to make
available for search inventions disclosed therein and additional to that
by which the patent has been diagnosed and classified.

A "digest cross-reference" is a cross-reference formed from abstracts or
extracts from a patent consisting of illustration and text cut from a
photolithograph of a patent and mounted.

A "search-card" is a sheet of the size of a photolithograph of a patent
placed with the photolithographs of patents forming a subclass in the
examining division and public search room, and containing suggestions
for further search, and on the copy for the search room, a definition of
the subclass.

"Search notes" are addenda to class and subclass definitions comparing
other classes and subclasses with the one defined and giving directions
for search when necessary to prosecute search beyond the defined class
or subclass.



(1) The basis of subdivision and assemblage of the means of the "useful
arts" in the Patent Office classification is "art" within the meaning of
"art" in section 4886, Revised Statutes. The direct, proximate or
necessary art, operation or effect, rather than some accidental and
remote use or application, should be selected. In all cases qualities or
characteristics that persist through all accidental uses and that can be
identified as permanent are to be preferred.

(2) The operative, instrumental, or manipulative arts, including
machines, tools, and manufacturing processes, should be classified
according to whether a single operation of one kind applicable to
various materials to be used for various purposes is carried out by the
claimed means, or whether plural operations are performed, which,
combined, produce a special effect or special product.

   Example: An instrument performing a plurality of operations
   peculiar to shoe-manufacture would be classified on the
   basis of shoemaking, because that instrument would be
   incapable of other use, while an instrument peculiarly
   adapted to drive nails would be classified on the basis of
   nailing, whether for nailing shoe-heels or other objects,
   and a hammer would be classified on the basis of its
   function as an impact tool even though described as for
   driving nails, and even into shoe-heels.

(3) Structures (passive instruments) will, in general, be classified on
the basis of structure, either of special or general application, the
essential functions and effects of static structures being resistive or
the maintaining of forces in equilibrium.

   Example: A structure recognized as peculiar to barriers of
   the kind known as fences would be classified in the special
   class of Fences, but posts, joints, beams, etc., recognized
   as having use in general building, even though described as
   used in fences, would be classified in a more general
   building class, such as Wooden Buildings or Metallic
   Building Structures.

(4) Compositions of matter and manufactured or formed stock or
materials will be classified in accordance with the inherent character
of the substance or material where possible, otherwise according to
special use.

   Example: A pure chemical is expected to be classified on
   the basis of its chemical structure and constituents, even
   though useful as a food, medicine, dyestuff, explosive,
   etc., and alloys on the basis of metallic composition, even
   though used for bearings, coins, tools, etc.; whereas a
   physical composition having no reason for existence except
   to function as a cleansing composition or a paint might
   have to be classified on the basis of its function as a
   detergent or a coating composition, respectively. Also a
   bimetallic layered foil, plate, or wire would be expected
   to be classified as metal stock even though designed for
   use for dental filler, plowshare, or electric conductor,
   and a woven textile fabric as a fabric even though
   described as used for a filter or apron for a paper-making


(5) The divisions or subclasses of a class should be made exhaustive,
i. e., they should be susceptible of receiving any future invention that
may fall within the scope of the class. The rule as usually phrased is:
"The constituent species must be equal, when added together, to the
genus." Exhaustive division may be secured by maintaining always a
residual or miscellaneous subclass. The miscellaneous subclass
represents the remainder of the original undivided material undefined
except as the class is defined and may be accurately treated as if it
had the class title.

(6) A second rule respecting the subdivision of a class is: "The
constituent species must exclude each other." That is, the divisions or
subclasses must not overlap. (See exception in Rule 8.)

   Example: If a number of balls of several different
   materials, several different conformations, or
   constructions, several different colors, were to be divided
   into glass balls, hollow balls, and red balls, this rule
   would be violated, because some balls would be glass,
   hollow, and red.

(7) A third rule respecting subdivision is: "The divisions must be
founded on one principle or basis." The application of this rule will
generally form divisions that do not overlap. (See exception in Rule 8.)

   Example: If a number of balls of several different
   constructions, several different materials, and several
   different colors were to be classified so as to provide a
   place for each kind of characteristic, they should be
   divided first, for example, according to construction into
   hollow balls and solid balls, each of these according to
   materials into glass balls, rubber balls, metal balls,
   wooden balls, etc., and each of the latter into red balls,
   blue balls, green balls, etc.

(8) When it is found that division into overlapping subclasses and on
different characteristics is a lesser evil than an unwieldy number of
subclasses that would otherwise result, then those subclasses based on
characteristics deemed more important for purposes of search should
precede in the list of subclasses those based upon characteristics
deemed less important. (See Rule 6.)

(9) In arrangement of subclasses or subdivisions the miscellaneous
groups containing material not falling within any of the specifically
entitled subclasses, should stand first; those subclasses defined by
effect or special use should precede those defined by function or
general use; those containing matter that is related to the matter of
other subclasses as whole to part should precede those subclasses that
contain the part; and those defined by a characteristic deemed more
important or significant for search purposes should precede those
defined by characteristics deemed less important.

_Whenever superior rank has been assigned to any selected
characteristic_ by placing divisions based upon it in advance of
divisions based upon other characteristics, _this superiority should be
maintained throughout_.

   Example: A partial schedule of Class 80 follows to
   illustrate the arrangement of subclasses:

    Class 80.--METAL ROLLING.

     1. Miscellaneous.        | 24. Die rolling--
     2. Heating and rolling.  | 25.   Oscillating rolls.
     3. Cutting and rolling.  | ..    ...
     4. Drawing and rolling.  |     Mills--
     5. Annular bodies.       | 32.   Coiling.
     6. Screw threads--       | 33.   Work reversing.
     7.   Concave and roll.   | 34.   Three or more coacting rolls.
     8.   Platen rolling--    | 35.   Continuous--
     9.     Dies.             | 36.     Inclined trains.
    10.   Rods and wires.     | ..      ...
    11. Tubes--               | 41. Roll cooling and heating.
    12.   Idle rolls.         | 42. Cooling beds.
    13.   Axial rolling.      | 43. Feeding--
    14.   Segmental rolls.    | 44.   Tables.
    15.   Skelping.           | ..    ...
    16. Wheels and disks.     | 55. Housings.
    17. Reworking.            | 56. Roll adjustments--
    18. Concave and roll.     | 57.   Relief devices.
    19. Platen and roll.      | 58. Rolls--
    20. Platen rolling--      | ..  ...
    21.   Disk platens.       | 60. Processes--
    22. Axial rolling--       | ..    ...
    23.   Pattern rolls.      | 66.   Flanged bars.

   In this schedule the miscellaneous subclass is numbered 1,
   then follow three subclasses (2-4) of rolling plus another
   function, then four major subclasses (5-16) of rolling,
   merely, but applied to blanks of special form producing
   special products, then one special subclass (17) based upon
   a special class of material treated, then five subclasses
   (18-31) specialized in type and mode of operation, then
   general types of rolling mills (32-40), then various parts
   and accessories (41-59), then processes (60-66). This is
   the usual arrangement and is an exhaustive division for the
   art of metal rolling. Had there been miscellaneous
   subclasses for all combined operations of rolling plus some
   other function, a miscellaneous subclass for all mere
   rolling machines, either special or general, and a
   miscellaneous subclass for all parts and accessories, the
   requirements of exhaustive division would have been also

   In the illustrative schedule, there being no miscellaneous
   subclass for means having combined functions of rolling and
   another, any patent having claims for the combination of a
   means for rolling and a means for cooling would fall in
   subclass 1, Miscellaneous. In that subclass would also fall
   all "Mills," such as for rolling spiral conveyer-flights,
   the same not falling under any of the subclasses 32-40, no
   miscellaneous subclass of "Mills" and no special
   article-rolling subclass having been provided; also all
   parts or accessories, such as a water-cooled screen,
   peculiarly adapted to rolling-mills, there being no
   existing subclass of screens therein and no miscellaneous
   subclass of parts. The arrangement of subclasses in Class
   80 requires that the combination of a furnace and a
   rolling-mill shall be placed in subclass 2, even if the
   combination be designed and adapted for rolling annular
   bodies (subclass 5) or tubes (subclass 11). Means special
   to rolling a tube between a concave and roll must be placed
   in subclass 13 rather than in subclass 18. A work-reversing
   mill must be placed in subclass 33 rather than in subclass
   34 even though it have three or more coacting rolls.

   The rolling of "Screw-threads" having been given higher
   rank than a "Concave and roll" mechanism, any concave and
   roll mechanism limited for use in rolling screw-threads
   should be formed into a subclass indented under
   "Screw-threads" and not into a subclass "Screw-threads"
   indented under "Concave and roll."

(10) Class schedules are arranged with certain subclasses appropriately
indented according to a commonly understood expedient. In a properly
indented schedule subclasses in column at the extreme left are the main
species (the proximate species) of the class. The titles and definitions
of all subclasses proximate to the class (at extreme left) must be read
with the title and definition of the class, as if indented under the
class title one space to the right; so also with the titles and
definitions of subclasses indented under other subclasses. If a title
has no number (as in Class 80, "Mills"), it represents merely a
subject-matter to be divided, assumed to have no representatives other
than those in the species indented under it. If a title having indented
species under it has a number, it not only represents a subject to be
divided but also a subclass including all other species not falling
within the indented titles. Indention does not indicate superiority or
inferiority, but merely that the title and the definition of the
indented subclass must be read with the title and definition of the
subclass under which it is indented. A title selected in a scheme of
subdivision to be of first importance and placed, therefore, in advance,
should not thereafter be indented under a title selected to be of
secondary importance and, therefore, having a lower position. (See Rule

(11) A group of material may be divided on several different bases.
"Use" or "purpose" or "object treated" may be adopted only when the
"use" or "purpose" or "object treated" stamps upon the invention such
peculiarities of operation or construction as to limit the applicability
of the invention to the use or purpose named. (See Basis of
Classification, Rule 1.) A group based upon mode of operation also may
be divided into subclasses (1) with a "functional" title, usually
participial in form, and adapted therefore to receive machines,
processes, and tools; (2) with special use, purpose, or object-treated
title containing the name of the use, purpose, or object; (3) with
"type" title, usually a name or a name with a qualifying adjective; (4)
with a title of a part or subcombination, also a name.

   Example: In Class 90, Gear-Cutting, Milling, and Planing,
   are to be found subclasses entitled "Gear-cutting," certain
   machines being peculiar to that use; also other subclasses
   with the general functional title "Planing," subordinate to
   which are the special use subclass "Planing, Soft metal,"
   and the type subclass "Planers" divided into two coordinate
   subclasses, "Reciprocating bed" and "Reciprocating cutter,"
   and several subordinate "part" subclasses, including
   "Tool-feeds" and "Tool-heads." The adjective form of the
   title "Planers, Reciprocating bed," indicates a type
   subclass. If the title had been Planers, Reciprocating
   beds, the indication would be that the subclass was a part
   subclass to receive planer beds only. In the class referred
   to for illustration, "Tool-feeds" and "Tool-heads" indicate
   subclasses for parts and not for types of planers having
   tool feeds.

(12) In arranging the divisions of a class, such arrangement should be
sought as will minimize the need of cross-references. Search for any
particular matter can not always be limited to one group without such
extensive cross-referencing as would in some cases defeat the purpose of
classification. Forming the subdivisions of a class according to the
total similarities of the inventions, rather than according to some
selected more or less important characteristic, and arranging them in
the correct order of superiority and inferiority, with care to maintain
throughout the schedule the relative positional values of the several
selected bases of division, will ordinarily in a closely bonded class
limit the search for any single invention to the subclass particularly
suited to receive it and some subclasses preceding that one, excluding
from the necessity of search the subclasses succeeding.

   Example: In Class 80, Metal-Rolling, it would not be
   expected to find any tube-rolling mill lower in the
   schedule than the tube-rolling subclasses, but a tube-mill
   might be found higher up in "Heating and rolling," "Drawing
   and rolling," etc. No concave and roll combination should
   be found succeeding the subclass of "Concave and roll," but
   it may be found under subclasses above, such as "Tubes,
   Screw-threads," etc. No rolls should be found lower than
   the subclass of "Rolls," but they may be found in many
   subclasses above.


(13) Having some knowledge of the nature of the materials about to be
classified, a tentative definition of a class to be formed may be
framed, which may be either written down or merely carried in mind, to
serve as a tentative guide. This tentative definition must be considered
as subject to change to any extent by the fuller knowledge obtained by
careful consideration of the material. After a full knowledge of the
materials to be classified has been acquired, it will be necessary to
frame a careful definition of the class, and also of each subclass whose
title does not unequivocally indicate what is contained in it.

(14) A definition of any class should state the "qualities and
circumstances possessed by all the objects that are intended to be
included in the class and not possessed completely by any other
objects." A proper definition should not ordinarily contain the name of
the thing defined. "Definitions in a circle" are, of course, worthless.
A definition should be exactly equivalent to the species defined and
should not be expressed in obscure or ambiguous language, but should
employ terms already defined or perfectly understood. It should not be
in negative form where it can be affirmative. If the class of objects
has a peculiar property, the naming of that may serve as a definition.
If no peculiar property can be detected, the definition should name more
than one quality or property. Several different classes may have one or
more properties alike, but as the number is increased the likelihood of
there being others having the same properties is decreased. The briefest
possible statement of such properties or qualities as are possessed by
all the objects of a class and not completely possessed by any other
objects, which will suffice to distinguish the class from other classes
and determine its position in the general classification, will be most
satisfactory. To define any species, the genus having been defined, the
genus should be named and the difference added. Of course, no generic
definition should contain any limitation not characteristic of every
species of the defined genus. In seeking qualities by which to describe
a genus or species, no accident should be selected.

   Example: Suppose there be marked out and defined as a genus
   all means whereby one form of energy is transformed into
   another form of energy and no more, and the genus be named
   energy-transformers. We may then name, as species,
   energy-transformers that are motors and energy-transformers
   that are not motors. Motors may be defined by merely naming
   the genus energy-transformers, and stating the difference,
   to wit, continuously transforming energy into cyclical
   mechanical motion. Then the definition will be:
   Energy-transformers that are adapted to continuously
   transform energy into cyclical mechanical motion. The
   non-motor division will retain the genus definition.

   It would not be illuminating for a searcher having little
   familiarity with the textile arts to look under the title
   "Carding" and find that carding is defined as a means for
   carding fiber.

   Even though the first steam-engine invented had been used
   to run a gristmill, the accident of its use as a part of a
   gristmill would hardly warrant the definition of a
   steam-engine as a means to grind corn. Nor would a hammer
   be properly defined as an instrument to drive nails or to
   crack nuts or to forge horseshoes, even though a patent
   should not mention any use other than one of these and
   should lay heavy emphasis on the special value of the
   hammer as a nut cracker, nail driver, etc.

(15) In those cases where the title is so obvious that definition is
superfluous, explanatory notes may be substituted and will usually be
found helpful.


(16) Inasmuch as nearly every patent discloses unclaimed matter that is
classifiable separately from the claimed matter, it is clearly
impossible to cross-reference every disclosure of every means in every
patent. Many things must be taken as conventional, obvious, or well
known, and the good judgment of the classifier is bound to be exercised
in cross-referencing matter disclosed but not claimed to be the
invention of the patentee.

(17) A mere part or element should rarely be cross-referenced from an
element class to a superior combination class. An element forming part
of a combination in a superior class should, if claimed, be
cross-referenced to the element class and also if not claimed if it
seems to be not merely a conventional form, and patents having claims
for more than one differently classifiable invention should always be
cross-referenced unless such an arrangement of subclasses with
search-notes is substituted as will guide the searcher to all places
where the material may be found. Claimed matter additional to that which
controls the classification, if belonging in the same class, should be
cross-referenced into a _succeeding_ subclass. Cross-references of
unclaimed disclosure may be in either direction.

(18) To supplement or take the place of cross-referencing, more or less
elaborate search-notes are needed, giving directions and suggestions for
further search, setting out the relationship between classes and
subclasses, and drawing distinctions by example. Search-notes should
indicate other classes or subclasses in which the subject-matter of the
group to which the search-notes are appended is likely to form a part of
a more intensive combination, also analogous matter that might serve as
a reference for a broad claim. They need not, in general, indicate where
parts or elements of the subject-matter which are common also to other
classes can be found, because the index of classes contains the
necessary information. For example, it is not necessary in every
machine-class to indicate by search-notes where machine-elements and
static parts may be found, nor in a class of wooden boxes to point out
where the nails, screws, hinges, or locks that may form a part of the
box are classified.


(19) Inasmuch as nearly every patent contains disclosure that is
claimed and also disclosure that is not claimed, it has been deemed
advisable to establish the general rule that where the claimed and
unclaimed disclosures are classified in different classes or subclasses
the invention both disclosed and claimed shall determine the placing of
a patent (or a pending application) rather than any selected invention
that may be disclosed but not claimed. "Not claimed" covers means that
may form an element only of a claim as well as means not referred to in
any claim. (See exceptions in Rules 21 to 22 inclusive.)

   Example: A patent discloses and claims a dash-pot but
   illustrates it in such relation to a metal-planing machine
   as to utilize it for checking the movement of the bed at
   one end of its path, or in connection with an electric
   generator to aid in effecting the brush adjustment; the
   patent should be classified in the subclass of Dash-pots.
   If the classifier finds the disclosed organization of
   dash-pots and planer or dash-pot and generator more than a
   conventional illustration of an obvious use, he should note
   a cross-reference to Planers or Electricity, Generation. A
   patent discloses an internal-combustion engine associated
   with a specific form of carbureter; the claims relate to
   the engine parts only; the class of Internal-Combustion
   Engines should receive the patent, and a cross-reference
   should be placed in Carbureters. A patent discloses and
   specifically claims the combination of a rail-joint
   comprising abutting rails, fishplates, and specific bolts;
   the patent goes to an appropriate class of rail-joints, and
   if the bolt is more than a mere obvious conventional bolt,
   a cross-reference should be noted for the appropriate
   subclass of Bolts.

(20) The totality of the claimed invention should be selected when
possible to determine the appropriate class in which to place a patent.
The entire expression of the invention will usually be set forth in the
most relatively intensive claim.[1] In a properly drawn patent there is
at least one claim that will serve as a mark to indicate the
classification of that patent.

(21) Where a patent discloses but does not claim a combination of proper
scope to be classified in a combination subclass and claims merely a
detail classified in a subclass lower in the schedule, both in the same
class, if the subclasses are so related that the combination always
involves the detail so that a search for the detail must necessarily be
made in the combination subclass, the patent may be placed in the
combination subclass. This avoids the need of a cross reference into the
combination subclass, and a lack of a copy in the detail subclass is
immaterial, as it is seen in the completion of the search through the
combination subclass. (See Rule 19.)

   Example: A patent for a saw-making machine discloses
   dressing, jointing, and gaging mechanisms; it claims
   dressing and jointing only. There is a subclass for
   dressing, jointing, and gaging, and a subclass for dressing
   and jointing. In this case the patent may be placed in the
   first-mentioned subclass, as that must be searched always
   when the second-mentioned one is searched, cross
   referencing in this situation being of little value.

(22) Where a subclass with a generic title has indented thereunder a
species type-subclass bearing the title of the generic subclass
qualified by a difference, any patent which claims an invention falling
within the genus subclass and discloses the qualification of the species
type-subclass should be classified in the latter whether or not the
entire disclosure is claimed. (See Rule 19.)


        Class 29.--METAL WORKING.
      Machine chucks and tool sockets--
         Cam closing--
   126.    Scroll--
   127.      Bevel pinion or ring.

   If a patent claimed only the scroll of a scroll-chuck, but
   disclosed it in connection with a bevel pinion and ring, it
   should be classified in subclass 127, Bevel pinion and
   ring, and not in subclass 126, Scroll, although if there
   were no disclosure of the bevel pinion and ring it would go
   in subclass 126. Any search for scrolls must be prosecuted
   through all subclasses that include "Scroll" in the title.

(23) Where, as in the case of patents that show and claim a combination
that as matter of common knowledge is not new except in one of its
elements, to classify a patent strictly in accordance with rule would
result in placing the patent where it would serve no useful purpose as a
reference and having to cross-reference it to a class where it would
serve a useful purpose, it is best to classify the patent in the class
to which the element would take it. (See Rule 19.)

   Example: A patent claiming a wheeled vehicle, broadly, in
   combination with an internal-combustion engine comprising a
   cylinder, a crank-case, a piston and suitably-connected
   crank, a valve opening into the crank-case, and a valve in
   the piston opening into the cylinder, may be advantageously
   classified as an internal-combustion engine notwithstanding
   the alleged invention is for a motor vehicle.

(24) In order to meet the situation respecting the classification of
those patents that indiscriminately claim an article of manufacture
defined only by the material of which it is made and those patents that
claim those materials, leaving to the specification information
regarding the designed uses, patents for articles defined only by their
ingredients specifically set forth may be placed in the composition of
matter or material class. (See Rule 19.)

   Example: A patent having a claim for a cutter made of an
   alloy of iron, tungsten, and manganese would be classified
   with Alloys; a patent claiming a box made of paper composed
   of two layers united by a solution of asphaltum should go
   to the class of Laminated Fabric and Analogous
   Manufactures, rather than to paper boxes; and a patent for
   a house having its exterior coated with equal quantities by
   volume of carbonate of lead and oxid of barium suspended in
   a vehicle of linseed-oil would be classified as a paint
   rather than as a house.

(25) An alleged process of utilizing a specifically-defined composition
or material which consists in merely applying it to the use it was
designed for may be classified as a composition or material rather than
as a process. (See Rule 19.)

   Example: A process of painting the bottom of a marine
   vessel which consists in applying thereto a composition
   consisting of sulphate of copper, powdered metallic zinc,
   chlorid of antimony, and hyposulphite of soda, in a vehicle
   of linseed oil, would be more usefully classified as an
   antifouling paint than as a ship, as the invention would
   hardly be distinguishable from a paint claimed as such and
   described for use on submarine surfaces.

(26) An alleged process consisting merely in the use of a
particularly-defined machine or similar instrument operating according
to its law of action will ordinarily be classified in the class or
subclass where the machine belongs. But if in addition to defining the
operation of a particular machine the claim also specifies acts not
performed by the machine, the classification should be in the class or
subclass in which the process belongs. (See Rule 19.)

   Example: Thus a claim for a method of rolling an iron plate
   which consists in passing an iron blank between a pair of
   rolls arranged horizontally in juxtaposition one above the
   other and geared together so as to rotate in opposite
   directions, and causing an idle roll supported in bearings
   on the roll-housings to bear against the central portion of
   the surface of one of the first pair of rolls on the upper
   side thereof, should be classified as a rolling-mill, while
   if to that claim were added the steps of doubling the sheet
   after one passage between the rolls, again passing between
   the rolls, again doubling, and then passing the now
   four-ply pack between the rolls sidewise or turned 90 per
   cent to the direction in which it had previously been fed,
   the classification should be with processes of sheet-metal

(27) In the absence of settled rules defining permissible joinder of
inventions, there may be in one patent claims for one or more or all of
the classes of invention named in the statute, to wit, machine, art,
manufacture, and composition of matter. There may also be claims to
several more or less related inventions in the same statutory class of
invention but each belonging to a different industrial art. (1) Where
different main classes are involved, the patent will be classified by
the most intensive invention, without regard to the statutory class to
which it belongs. (2) Where different subclasses of the same class are
involved, the patent will be classified in that one of the several
subclasses defined to receive the several inventions which stands
highest in the schedule of subclasses.

(28) Where a patent contains claims for all or a plurality less than all
of the statutory classes, the general rule of preference or superiority
of the several classes of subclasses is that represented by the
following order, to wit: (1) Machine (or other operative instrument);
(2) Art; (3) Manufacture; (4) Composition of matter. This order is, in a
general way, the order of intensiveness of the several kinds of
invention. (See Rules 29-35.)

   Example: An automatic screw-machine, peculiarly adapted to
   carry out a process of making a novel form of machine-screw
   out of a new iron alloy, and having a claim to the machine,
   to the process, to the screw, and to the alloy, would be
   assigned to Metal-Working, Combined machines, and, if all
   claims were allowed, cross-referenced to Bolt and
   rivet-making processes, to Bolts, and to Alloys. If the
   claim to any one or two of the subjects were eliminated,
   the order of preference or superiority and the order of
   cross-referencing would remain the same.

(29) Patents containing a plurality of claims for several different
statutory kinds of invention that are classifiable in different main
classes, and wherein the rule of relative intensiveness varies from the
order Machine, Art, Manufacture, and Composition of matter, may be
diagnosed and classified as directed in the following paragraphs (30 to

(30) Where a patent contains claims for a process and for an apparatus
susceptible of use as an instrument in carrying out the process, but not
peculiar to that use, or for an apparatus adapted to carry out but one
step or only a part of the process, the process claim, being in this
instance the more intensive, would control the classification. (See Rule

   Example: In a patent containing a claim for a process of
   roasting ore and then collecting the fumes, and another
   claim for a roasting furnace that is a mere
   material-heating furnace, the process claim would control;
   whereas, if one claim were for a method of roasting ores
   consisting of stirring the ore, applying heat to the same,
   and collecting the solids from the fumes, and the other
   claim, were for a heating furnace having a stirrer and a
   fume arrester, the apparatus claim would control. And if a
   patent contained claims for a process of roasting ores, and
   other claims for a furnace susceptible of use in carrying
   out the process but equally useful in annealing glass or
   steel articles, the process claim would control.

(31) Where a patent claims a specified article of manufacture or other
product, and also an instrument for making a part only of that specified
article or other product, the product claim, being more intensive,
should control the classification; so also in case of a claim for a
product and a claim for an instrument performing any minor act with
respect thereto. (See Rule 28.)

   Example: Where a patent claims a particular construction of
   a riveted joint, and also a tool for calking the rivet, and
   where a patent claims a particular construction of shoe,
   and also a buttonhook for buttoning said shoe, the article
   and not the tool claims control.

(32) Where a patent contains claims to a process and a product, the
process claims govern the classification in those cases where search
among machines for making the product would have to be made, and such
processes would be classifiable on the basis of the mode of operation,
usually in the same class with machines for practicing such processes.
(See Rule 28.)

   Example: A patent having a claim for a process of making
   bifocal lenses, consisting in grinding the surface of one
   piece of glass to form a convex lens, heating another piece
   of glass until it is plastic, then forcing the ground
   surface of the first-named piece into the body of the
   latter and gradually cooling the lens-blank thus formed;
   and also a claim for a bifocal lens composed of two pieces
   of glass weld-united, would be classified in
   Glass-manufacture and cross-referenced into lenses. Or a
   patent having a claim to a process of making a metal plate
   with elongated perforations, consisting in forming round
   perforations in the plate and subsequently rolling the
   plate, thereby thinning and elongating the plate and
   elongating the openings, and also a claim to a metallic
   plate having relatively long and narrow perforations, would
   be classified on the basis of the process claim.

(33) Where a patent claims both process and product, and the alleged
process is disclosed in the product, so that search would have to be
made in the appropriate class of products, the product will be adopted
as the basis of classification, and classification will be in the
appropriate product class. (See Rule 28.)

   Example: A claim for a process of making a pencil
   consisting in assembling a core of graphite with a
   sheathing of wood, and attaching a cap of
   rubber-composition to one end, would be classified as a
   pencil rather than as a process, became conception of the
   article is inseparable from the process and search must be
   made in the article class.

(34) Where a patent claims a process of making a composition of matter,
and also the composition of matter, the claims will be classified in
general in accordance with the classification of the composition of
matter in all cases where the process is peculiarly adapted to produce
the composition, as by setting forth the introduction or assemblage of
particular ingredients, since those processes that include the selection
of particular ingredients necessitate search among compositions having
such ingredients. (See Rule 28.)

   Example: A patent having a claim for a composition
   consisting of a mixture of caoutchouc and casein, and a
   claim for the process of preparing a rubberlike substance
   which consists in adding undissolved raw caoutchouc to
   casein and thoroughly mixing and kneading the mass, would
   be classified according to the composition.

(35) Where a patent claims a product such as a specific article of
manufacture, or a specific composition of matter, and also claims a
process of general application for making one of the parts of the
article or one of the ingredients of the composition, the product claim
should control the classification. (See Rule 28.)

   Example: If a patent claimed a woven textile fabric having
   the yarns interlaced in a defined relation, and a process
   of spinning a yarn utilized in the fabric; or if a patent
   claimed a varnish composed of shellac, dissolved in wood
   alcohol, and a pigment, and also contained a claim for
   distilling wood to obtain the alcohol, the product claim
   would control the classification in each instance, and the
   process would be cross-referenced.

[1] All terms have a meaning in extension and in intension. The meaning
of a term in extension consists of the objects to which the term may be
applied; its meaning in intension consists of the qualities necessarily
possessed by objects bearing that name. The term "motors" in extension
means all motors--electric, gas, water, spring, weight, etc. "Motors" in
intension means instruments to convert some form or manifestation of
energy into periodical or cyclical motion of a body. As the intension
increases the extension decreases, and vice versa. There must be more
motors than there are electric motors, and electric motors have more
qualifications than are common to all motors. Comparison of arts and
instruments with respect to their extension and intension for
classification purposes should be made between comparable qualities. A
claim for a steam-engine may be very specific while a claim for a reaper
may be very broad; here there is no comparable relationship, and the
terms intensive and extensive do not have the relative significance most
useful in classification. But when a patent or application contains
claims for mechanism peculiar to electric motors and other claims for
mechanism common to electric motors and other kinds of motors, the
claims for the electric motor would control the classification.


(1) Do not start to make a new class or revise an old one with
preconceived fixed notions respecting its scope and the particular
subdivisions required. Wait until all patents pertinent to the subject
have been seen and adequate knowledge of them acquired. In other words,
make no _a priori_ classification but discover and assemble all the
facts and from them make your inductions. Then the common
characteristics of the subject-matter of the class may be intelligently
defined, the limitations of the class marked out, and its relation to
other classes set forth. Bear in mind that the Patent Office
classification deals with the subject-matter of the useful arts rather
than merely with existing classes, and that it is not therefore
essential to retain classes that are found to be composed of unrelated
or too distantly related units.

Assuming that the work of reclassification is undertaken by examiners
who are already experienced in the subject-matter to be classified,
procedure as follows is recommended:

(2) Utilizing your previously acquired knowledge of the patents in the
class you are about to revise, subdivide the existing subclasses into
bundles, so as to assemble in each bundle those patents deemed to have
the closest resemblance to each other. For the purpose of this
assemblage, consider each patent as an entirety and not with reference
to various more or less important parts of that entirety.

   Example: An apparatus comprising in alleged combination a
   means for decanting water, a means for electrolytically
   depositing impurities, and a means for filtering the water,
   should not be classified either as a decanter, an
   electrolytic apparatus, or a filter, but should be
   classified as a combination apparatus (taking it to the
   general art of liquid purification). So also the
   combination of a rotary printing-press with a folding
   mechanism, and a wrapping mechanism, should not be
   classified merely as a rotary printing-press, a folding
   machine, or a wrapping machine, but should be classified as
   a combination of the several mechanisms as an entirety
   whose functions carried out in proper order produce a
   printed and wrapped newspaper.

(3) Write an approximate or tentative definition of the matter thus
assembled in each bundle and attach it to its appropriate bundle.

(4) Where it appears that the subject matter of any bundle formed from
the patents of any subclass is analogous to matter in other subclasses
of the same class or in other classes, a note should be added to that
effect so that this matter may be given special consideration.

(5) When the same examiner or different examiners are working on
different subclasses containing analogous matter, parallel lines of
subdivision should be followed wherever possible, in order to effect an
arrangement that will facilitate comparisons.

(6) When subdividing a group of more or less complex organized structures
or mechanisms, note should be taken of subcombinations that form or it
is thought should form the basis of other subclasses, either in the same
or different classes, into which those details may be collected, either
classified therein originally or by cross-reference.

   Example: Assuming that the combination of press, folder,
   and wrapping mechanism, referred to in a preceding
   paragraph is to be classified in a class of Printing, on
   the entirety as a combination having the function of
   printing, plus other functions, and that folding and also
   wrapping are separately classified, then the particular
   type of press should be selected to be cross-referenced
   into a press-type subclass of the class of Printing, such
   as "Presses, rotary," while the folding mechanism and the
   wrapping mechanism would be noted for cross-reference to
   other appropriate classes. Also, any part of the printing
   press, such as the inking mechanism, specifically
   described, should be noted for cross-reference into a
   subclass of Printing designed to receive the inking
   mechanism as a part of the printing press.

(7) After a knowledge of the material of the class has been obtained by
estimating the resemblances between the individual patents that have
been assembled in the several groups, comparison of these groups,
represented by the bundles of photolithographs, by the aid of the
approximate definitions and notes attached can be made. It can then be
decided whether all of these groups are to be retained in the proposed
class, and the retained groups can be organized into a class with the
subclasses arranged so as to bring those subclasses having the strongest
resemblances in closest relation, and in such order as to comply with
the conventions adopted in the official classification. It will probably
be necessary to have one subclass or group as broad as the definition of
the class, to take unclassifiable matter and to provide for possible
future inventions.

(8) Up to this point, more or less cursory attention may be given
individual patents; but when an arrangement of subclasses shall have
been tentatively adopted it will be necessary to consider each patent
carefully to ascertain whether it is properly placed.

(9) Patents that, considered as an entirety, cover means not peculiar to
the class or subject-matter being revised, should, in general, when
assembled in groups as indicated, have a note attached indicating not
only want of limitation to the subject-matter of the class but also a
more appropriate class to receive them if such there be. Although a very
large proportion of patents can be accurately classified as indicated by
their titles and stated uses, the mere fact that in a patent found in a
class the invention is called in the specification or claims by a name
peculiar to the class is not of itself a reason for considering it
peculiar to the class. A gas and liquid contact apparatus may be called
a heater, a cooler, a gas-washer, a water-carbonator, a condenser, a
disinfecter, an air-moistener, and so on, depending upon accident of
use. If there are not elements in some claim to confine the means
described distinctively to what it is called, or if there are no
functions necessarily implied in the means claimed peculiar to the named
use, the patent should not be kept in the class unless there is no other
class in the office that can receive it.

   Example: Where the matter claimed is a metal beam of
   peculiar cross-section, it should be classified with other
   metal beams, as in Class 189, Metallic Building Structures,
   even if it is named in the application as a beam of
   particular use, as a railroad-tie, car-sill, bridge-tie,
   etc. Should a mere dash-pot be found classified in Class
   171, Electricity, Generation, a note should be attached
   indicating that it belongs in the appropriate element

(10) In giving this final careful attention to the patents, each should
also be scanned to see whether it contains matter that should be
cross-referenced. A few lines obscurely located in a specification may
contain a disclosure of a most valuable invention. No class can be
deemed complete until the disclosures appropriate to it found as parts
of more complex inventions in other classes, or disclosures of analogous
matter in other classes, are either cross-referenced into it or cross
search-notes made.

(11) To indicate cross-references, from one subclass to another within
the class or from the class under consideration into another class,
attach a small slip of paper to the patent and mark on the slip the
subclass number in which the cross-reference shall be mounted. If the
matter to be cross-referenced relates only to a portion of a voluminous
patent, the portion of the specification and drawing to be
cross-referenced should be indicated. If the cross-reference falls
outside the class, the class number should be noted in addition to the
subclass number.

(12) Should it be found that the handling of copies in making
examinations detaches the cross-reference slips, it may be advisable to
mark lightly but legibly in pencil on the lower right-hand corner of the
examiner's photolithograph the number of the subclass or subclasses into
which it is to be cross-referenced, or the number of the class and
subclass in case it is to be cross-referenced to another class.

(13) Whether cross-reference notations are written on a separate slip or
on the photolithograph, the number of the class and subclass into which
a patent is to be cross-referenced should always be preceded by X (thus
X 101-23) in order to distinguish the original classification notation
from the cross-reference notation and enable sorting and indexing to be
done without confusion.

(14) To indicate cross-references from other classes into the one being
reclassified, set down the number of the patent in a notebook, placing
after the number (1) the class and subclass in which it is classified;
and (2) the number of the class and subclass in which it is to be

(15) Should new subclasses be formed or transfers of patents be
determined on, and lists of the patents, instead of copies thereof, be
furnished clerks for the purpose of making such subclasses and transfers
and correcting the official indexes and other records, each patent
should be listed by number in column to the left of a sheet of paper or
notebook, and opposite each patent number on the same sheet should be
written (1) the number of the class and subclass in which it is
officially classified; (2) the number of the class and subclass to which
it is intended to transfer it; and (3) the numbers of the classes and
subclasses, preceded by X, into which it is intended to cross-reference

   Note: Even though examiners engaged in reclassifying are
   confident of their ability to classify and arrange on
   better principles than those that have been applied thus
   far in the classification, they ought, nevertheless, to
   follow those principles under which one-half of the patents
   have been classified. Until the Commissioner of Patents
   orders examiners to classify on other principles, it is
   expected they will follow those now established.

 | Transcriber's Note:                                             |
 |                                                                 |
 | Every effort has been made to replicate this text as faithfully |
 | as possible, including obsolete and variant spellings and other |
 | inconsistencies.                                                |
 |                                                                 |
 | For readability, the footnotes have been moved to the end of    |
 | the relevant chapter.                                           |
 |                                                                 |

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