[6] The matters thus marked are dealt with more fully under the Division on Reference Work, but are included here for the sake of giving a complete conspectus of the material involved in selection.--ED. =199. Discarding Effete Books.=--The question of periodically weeding out a public library, with the object of keeping it always up to date and also making room for fresh additional stock, has already been partly discussed in Sections 107, etc., and 174, etc., and it is a most important part of modern public library policy. The periodical reprinting of class lists affords a valuable opportunity for considering the claims of certain kinds of books to remain idle on the shelves, where they not only fill the space which should be available for more live works, but they obstruct the general work of the library. Every public library receives at one time or another books which must for reasons of policy be catalogued. Such books, for example, as are donated, are expected to be placed in the library and duly catalogued. There are generally hundreds of such books in every large library which have no permanent value; and these, and also the mistaken selections of committees and librarians, should be discarded as soon as possible. There are also, of course, the books which go out of use automatically, such as those noted in the subjoined Rules, and those others which manage to slip into libraries when the custodian is dreaming of higher things, or is misled by the erroneous titles adopted by authors. The weeding-out process should be continuous, and when catalogues are being reprinted, the books are being rearranged, or any kind of fresh movement is being made, a specially favourable opportunity is afforded to prune the growth of weeds which will somehow manage to infest the best-regulated libraries in spite of every care. The sentimental museum idea is, of course, responsible for much of the tendency to collect and preserve everything, on the Byronic theory, no doubt, that A book’s a book, although there’s nothing in’t, and, as a library is a repository for books, then _all_ books should be collected and preserved at any hazard or sacrifice, be they good or bad. =200.= RULES FOR DISCARDING USELESS BOOKS: SCIENCE.--All general works which are not epoch-making, but merely recapitulations of ascertained facts, should be discarded when twenty years old. Care should be taken not to discard any book, however old, which has not been efficiently superseded. All ordinary text-books of every science, save mathematics and occult science, may be discarded when twenty years old. Nicely illustrated textbooks, especially of zoology and botany, should be discarded with much caution. USEFUL ARTS.--The same rule applies to this class as to Science, save that patents, specifications, recipes, books on household arts, and all finely illustrated books should be retained.