Dana, J. C. Accessioning Books. _In his_ Library Primer, 1910, p. 81. Dewey, Melvil (_Ed._). Library School Rules, 1892. Hitchler, Theresa. Accession Record, etc. _In her_ Cataloguing for Small Libraries, 1915. A.L.A. Hopper, F. F. Order and Accession Department. _In_ A.L.A., Man. of Lib. Econ. Preprint of chapter xvii., 1911. Jast, L. S. Accessions: The Checking of the Processes, 1909. Roebuck and Thorne. Primer of Library Practice, 1914, chapters ii.-iii. Sayers and Stewart. Book Selection and Ordering; Stock Register. _In their_ The Card Catalogue, p. 66. For articles, see Cannons, G 25-38, Preparation of Books for the Public, etc. DIVISION VII CLASSIFICATION AND SHELF ARRANGEMENT CHAPTER XV GENERAL PRINCIPLES =230.= There is no more important factor in the success or failure of a library than the classification of the books and other material which form its stock. Some of its uses are obvious to all readers; it brings the material on any subject together on the shelves and in the catalogues, and thus enables both librarian and reader to find books readily. It has perhaps more important uses, because it enables the librarian, and, in open access libraries, the public, to see the strength and weakness of the collection in various subjects; it, therefore, is the only safe and certain means by which a collection may be built up systematically, and may be increased. Moreover, it reveals the obsolete books merely by bringing them into juxtaposition with books which have superseded them. An imperfectly classified, or unclassified, library resembles chaos as nearly as anything can do, and want of classification renders the finest collection of books useless except to those who already know all there is to be known of any subject in which they may be interested, and who can therefore find the books by other means. In short, classification is the primary key to the assembling, finding, selecting and rejecting of books. =231.= It does even more than this. A perfectly or logically constructed classification shows not only all the books on a specific subject; it also shows the books which are collateral, or which lead up to and away from the books on the specific subject. It will readily be seen, therefore, that the art of classification is one that must be understood thoroughly by the successful librarian. Several text-books have been written on the subject, and many articles have appeared advocating and criticizing various systems. We can give here only a few leading principles, and afterwards discuss the four or five schemes which have received most general recognition from librarians.