d the process is repeated as often
as necessary. Thus 512 means Class 5 (Natural science), Division 1
(Mathematics), Section 2 (Algebra), and every algebra is numbered 512.

The books on the shelves and the cards in the subject catalog are
arranged in simple numerical order, all class numbers being decimals.
Since each subject has a definite number, it follows that all books
on any subject must stand together. The tables show the order in which
subjects follow one another. Thus 512 Algebra precedes 513 Geometry,
and follows 511 Arithmetic.

In the book after the tables of the classes arranged in their
numerical order is an index, in which all the heads of the tables
are arranged in one simple alphabet, with the class number of each
referring to its exact place in the preceding tables. This index
includes also, as far as they have been found, all the synonyms or
alternative names for the heads, and many other entries that seem
likely to help a reader find readily the subject sought. Though the
user knows just where to turn to his subject in the tables, by first
consulting the index he may be sent to other allied subjects, where he
will find valuable matter which he would otherwise overlook.

The claims of the system may be summed up as follows: compared
with other systems it is less expensive; more easily understood,
remembered, and used; practical rather than theoretical; brief and
familiar in its nomenclature; best for arranging pamphlets, sale
duplicates, and notes, and for indexing; susceptible of partial
and gradual adoption without confusion; more convenient in keeping
statistics and checks for books off the shelves; the most satisfactory
adaptation of the card catalog principle to the shelves. It requires
less space to shelve the books; uses simpler symbols and fewer of
them; can be expanded, without limit and without confusion or waste of
labor, in both catalogs and on shelves, or in catalogs alone; checks
more thoroughly and conveniently against mistakes; admits more readily
numerous cross references; is unchangeable in its call-numbers, and so
gives them in all places where needed, as given in no other system;
in its index affords an answer to the greatest objection to class
catalogs, and is the first satisfactory union of the advantages of the
class and dictionary systems.

The Decimal system is used by a large number of libraries in this
country, and has gained recognition and has been put to use by some