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.

(C) RULES OF CLASSIFICATION.

BASIS OF CLASSIFICATION.

(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-man