=257. Kinds of Catalogue.=--There is no more important decision that a librarian has to make than that of the form which the catalogue is to take. A wrong choice here will produce months of labour to make good the error. The choice will no doubt be influenced by the kind of public for which the catalogue is required. The public may be general in character, and within that somewhat vague definition may be artisan, or commercial, or what not; or it may be special--with a large number of students. The public a municipal library has to serve usually combines all these elements; and in choosing the form of catalogue, a librarian may be guided by the desire to serve them all, but to emphasize the educational side of his work. The questions which a catalogue or catalogues may be expected to answer are: what books has the library (_a_) by a given author, (_b_) on a given subject, (_c_) having a given title. Most catalogues may, by the addition of indexes, be made to yield this information with varying degrees of efficiency. The various forms, and examples of them, should be considered carefully before the choice is made. Those most recognized are the _Author_ catalogue, the _Dictionary_ catalogue, the _Classified_ catalogue, and the _Alphabetical-Classed_ catalogue. The _author_ catalogue is most valuable in the hands of literary men and of experts, but is of very limited use to the reader whose knowledge of authors is small. It is simply an alphabetical arrangement of author entries of books, without any reference in that arrangement to their subjects. The best examples of this form of cataloguing are the British Museum _Catalogue of the Printed Books_ and the _Author Catalogue_ of the London Library.