# A Library Primer (1899)/Chapter XXI

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 A Library Primer by John Cotton Dana Chapter XXI, Decimal classification
[From the Introduction to the Decimal classification and Relative index. Published by the Library Bureau, \$5.]

The field of knowledge is divided into nine main classes, and these are numbered by the digits 1 to 9. Cyclopedias, periodicals, etc., so general in character as to belong to no one of these classes, are marked nought, and form a tenth class. Each class is similarly separated into nine divisions, general works belonging to no division having nought in place of the division number. Divisions are similarly divided into nine sections, and 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 librarians and men of science in Europe.

Divisions
 000 General Works 010 Bibliography. 020 Library Economy. 030 General Cyclopedias. 040 General Collections. 050 General Periodicals. 060 General Societies. 070 Newspapers. 080 Special Libraries. Polygraphy. 090 Book Rarities. 100 Philosophy 110 Metaphysics. 120 Special Metaphysical Topics. 130 Mind and Body. 140 Philosophical Systems. 150 Mental Faculties. Psychology. 160 Logic. 170 Ethics. 180 Ancient Philosophers. 190 Modern Philosophers. 200 Religion 210 Natural Theology. 220 Bible. 230 Doctrinal Theol. Dogmatics. 240 Devotional and Practical. 250 Homiletic. Pastoral. Parochial. 260 Church. Institutions. Work. 270 Religious History. 280 Christian Churches and Sects. 290 Non-Christian Religions. 300 Sociology 310 Statistics. 320 Political Science. 330 Political Economy. 340 Law. 350 Administration. 360 Associations and Institutions. 370 Education. 380 Commerce and Communication 390 Customs. Costumes. Folk-lore. 400 Philology 410 Comparative. 420 English. 430 German. 440 French. 450 Italian. 460 Spanish. 470 Latin. 480 Greek. 490 Minor Languages.
 500 Natural Science 510 Mathematics. 520 Astronomy. 530 Physics. 540 Chemistry. 550 Geology. 560 Paleontology. 570 Biology. 580 Botany. 590 Zoology. 600 Useful Arts 610 Medicine. 620 Engineering. 630 Agriculture. 640 Domestic Economy. 650 Communication and Commerce 660 Chemical Technology. 670 Manufactures. 680 Mechanic Trades. 690 Building. 700 Fine Arts 710 Landscape Gardening. 720 Architecture. 730 Sculpture. 740 Drawing, Design, Decoration. 750 Painting. 760 Engraving. 770 Photography. 780 Music. 790 Amusements. 800 Literature 810 American. 820 English. 830 German. 840 French. 850 Italian. 860 Spanish. 870 Latin. 880 Greek. 890 Minor Languages. 900 History 910 Geography and Description. 920 Biography. 930 Ancient History. 940 Modern Europe. 950 Modern Asia. 960 Modern Africa. 970 Modern North America. 980 Modern South America. 990 Modern Oceanica and Polar Regions.