=175. The first point which occurs is the connexion between a library’s income and its book-purchasing power. As, by law established, most British library incomes are strictly limited, it follows that a similar limitation must govern the supply of books, and that only a _selection_ of new books can be procured, old and out-of-print books taking their chance. The very largest rate-supported libraries are bound by this limitation to buy only a selection from the immense mass of books annually published, and, even if such purchases amount to several thousands of volumes, they represent only a _selection_. The smaller libraries must of necessity make a selection within a selection, and it follows that, in all cases of libraries supported by small incomes or burdened by heavy charges for the repayment of loans or other purposes, the selection must be carefully made if it is to be representative of all that is best in ancient and modern literature. Another factor which enters into the matter need only be mentioned in order to be dismissed: that is the obvious unsuitability of a very large proportion of the books annually published because of their form (pamphlets and tracts), subject-matter (school-books, bibles, etc.), or special nature (local lists, reissues, directories, etc.). =176.= The fund available in most public libraries for the purchase of books can be made the basis for a rough calculation showing at what rate libraries of different sizes should grow. By reference to the tables in Section 31 it will be found that the sum which can be annually expended on books is limited in libraries of all sizes, and that the annual additions must of necessity follow the same limitation. =177.= The annual production of new publications in the United Kingdom may be taken at about 10,620 volumes, including everything, and the number of new books in this total may be averaged at about 8300 volumes. It will thus be seen that the British municipal libraries must be _selectors_ rather than _collectors_ of books, because the income of no one of them is equal to buying more than a proportion of the 8300 new books published annually in Britain alone. Some English public libraries, because of their accumulations of old, useless and effete books, resemble gardens choked with weeds; and their efficiency is clogged by the necessity for storing and caring for books which are of no value or interest. The presence of such books in a modern library hinders effective use and administration, because they occupy space urgently wanted for more useful modern books; they add enormously to the cost of cataloguing and charging; and in other ways they use up the resources of the library without adding to its public utility.