The Subject Catalogue on large cards can be used to advantage only with
the aid of the _Classification_ or _Index_. To find what the library
has on any given subject, get from the Index the class number of that
subject. Under this number in the Subject Catalogue will be found the
full titles of the books, with imprints, cross references, and notes. The
class number, by which the cards are arranged, is given in the upper
left corner and immediately under it is the book number. Any other class
number given in the left hand margin refers to another subject of which
the book also treats. When the class number at the top is followed by an
additional figure in brackets, the subject as given in the printed scheme
has been subdivided in arranging the cards. This subdivision will be
found on the first card of the catalogue which bears this class number.
These figures in brackets determine the arrangement of the titles in the
Catalogue, but on the shelves, in the Shelf Catalogue, and in calling for
and charging books, they are entirely disregarded. Thus a book numbered
942(7).14 would be in the Catalogue among the 942 cards arranged by the
figure in brackets as though it were a decimal, but it would be called
for as 942.14, the brackets indicating that the final classing was
limited to the Catalogue and was not extended to the shelves. If a fourth
figure is added without brackets, the final classing is extended to the
shelves as well as to the catalogue, and all the figures must be used
in calling for the book. In such cases the added figure is treated as a
decimal in the arrangement, though the decimal point is not written.
The last card which bears any class number, gives under that number,
followed by the word SEE the call numbers of other books which treat of
the same subject, but are classed elsewhere. General cross references
are also made in many cases without specifying individual books, as from
_Commerce_ as a question of SOCIAL SCIENCE (380) to _Commerce_ as a
USEFUL ART, Book-keeping Business Manuals, etc. (650). In such cases
there is a card under 380 marked SEE 650, and under 650 there is a card
marked SEE 380. From whatever stand-point a subject is approached, the
cross references guide at once to the same subject treated in its other
relations. These cross references both general and specific are often
accompanied by brief notes, characterizing the books to which reference
is made.
There will be found at the beginning of many class numbers, a card noting
the most reliable books on that subject, and the best of the articles in
periodicals, transactions, and collected works with the volume and page
where they may be found. It is hoped to give special prominence to these
notes for the guidance of readers, and they will be added as rapidly as
other duties allow.
Many subjects will have no sub-section cards at the beginning; some will
have no reference cards at the end; and some may have no titles given
under the number. The scheme provides a place for books on all subjects,
whether the library has them or not, so where no titles are given under
a class number it shows that the library has as yet no books on that
subject.
Articles in periodicals and transactions, separate volumes of sets and
collections which are located together, _if catalogued_ are put under
their proper subject number, but no _book number_ is given with it. The
call number of the book, where they may be found, is always given in the
margin preceded by the word IN. In the same way special chapters in books
will sometimes be catalogued, _e.g._ a card marked 338 IN 331-27, would
mean that in the 27 books on 331, _Capital and Labor_, there was a
chapter on 338, _Production_.