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."

DIVISION AND ARRANGEMENT.

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