turing for 20 years. Before it was
printed it was applied (with a different notation) to the arrangement
of a library of over 150,000 v. The experience thus gained has been
supplemented as each part was prepared for the press by searching
catalogs, bibliographies, and treatises on the subject classified.
This ensured fullness. Overclassification, on the other hand, has
been guarded against in four ways: 1) By not introducing at all
distinctions that are purely theoretical or very difficult to apply;
2) by printing in small type those divisions which are worth making
only when a large number of books calls for much subdivision; 3) by
warning classifiers in the notes that certain divisions are
needed only in large libraries; 4) by printing separately seven
classifications of progressive fullness, the first having only 11
classes, which would be enough for a very small library; the second
having 15 classes and 16 geographical divisions, suiting the small
library when it has grown a little larger; the third having 30 classes
and 29 geographical divisions; and so on, till the seventh would
suffice for the very largest library. The same notation is used
throughout, so that a library can adopt the fuller classification with
the least possible change of mark.

It often suggests alternative places for a subject, stating the
reasons for and against each, so that classifiers have a liberty of
choice according to the character of their libraries, or of their
clientage, or their own preferences.

The notation

The original feature of this notation is the use of letters to mark
non-local subjects and figures for places. This makes it possible to
express the local relations of a subject in a perfectly unmistakable
way, the letters never being used to signify countries, and the
figures never being used for any other subjects but countries. Thus 45
is England wherever it occurs; e.g. F being history and G geography,
F45 is the history of England, G45 the geography of England. This
local notation can be used not merely with the main classes, but in
every subdivision, no matter how minute, which is worth dividing by
countries. Whenever one wishes to separate what relates to England
from other works on any subject one has only to add the two figures
45. Whenever one sees 45 in the mark of a book one knows that the book
so marked treats its subject with special reference to England. This
"local list" by the figures from 11 to 99 gives