the Library of Fine Art; Class 2, the Library of Theology. These special
libraries or Classes are then considered independently, and each one is
separated again into nine special Divisions of the main subject. These
Divisions are numbered from 1 to 9 as were the Classes. Thus 59 is the
9th Division (Zoology) of the 5th Class (Natural Science). A final
division is then made by separating each of these Divisions into nine
Sections which are numbered in the same way, with the nine digits. Thus
513 is the 3d Section (Geometry) of the 1st Division (Mathematics) of the
5th Class (Natural Science). This number, giving Class, Division, and
Section, is called the Classification or Class Number, and is applied to
every book or pamphlet belonging to the library. All the Geometries
are thus numbered 513, all the Mineralogies 549, and so throughout the
library, all the books on any given subject bear the number of that
subject in the scheme. Where a 0 occurs in a class number, it has its
normal zero power. Thus, a book numbered 510, is Class 5, Division 1,
but _no_ Section. This signifies that the book treats of the Division 51
(Mathematics) in general, and is not limited to any one Section, as is
the Geometry, marked 513. If marked 500, it would indicate a treatise on
Science in general, limited to _no_ Division. A zero occurring in the
first place would in the same way show that the book is limited to
_no_ Class. The classification is mainly made by subjects or content
regardless of _form_; but it is found practically useful to make an
additional distinction in these general treatises, according to the form
of treatment adopted. Thus, in Science we have a large number of books
treating of Science in general, and so having a 0 for the Division
number. These books are then divided into Sections, as are those of the
other Classes according to the form they have taken on. We have the
Philosophy and History of Science, Scientific Compends, Dictionaries,
Essays, Periodicals, Societies, Education, and Travels,--all having the
common subject, =NATURAL SCIENCE=, but treating it in these varied forms.
These form distinctions are introduced here because the number of general
works is large, and the numerals allow of this division, without extra
labor for the numbers from 501 to 509 would otherwise be unused. They
apply _only_ to the general treatises, which, without them, would have a
class number ending with two zeros. A Dictionary of Mathemat