8.—What books have you in a particular literature? say French. (This is a somewhat remote but not unreasonable question.)
9.—Have you a book (author unnamed) bearing a particular title? and, on the same footing with this inquiry, Have you any of the series called so and so?
10.—What books have you in a particular form of literature? as poetry.
11.—Have you a novel or other work by a particular author dealing with a particular period? or any similar question relating to the inner nature of a book.
12.—In what volume of an author's works is a particular essay contained? (This last question is really the same as the first in another form.)
The first and second questions will be answered by a catalogue consisting of author-entries, that is a dictionary of authors, or if compiled under the British Museum rules it will answer these and the third also to a large extent. In addition it should answer No. 12. Questions 4, 5, 6, and 10 can be answered by means of the catalogue known as classified—the entries being arranged in general classes and sub-divided as necessary, but logically, according to the scientific relations of the subjects of the books. If an author-index is added other questions also would be answered with a little trouble. The same questions will be answered by the form known as alphabetico-classed—that is a catalogue of subject, class, and form entries arranged alphabetically.
No one style of catalogue, however, will answer all of these questions, but the one that will answer most of them with the least trouble and loss of time to the user is that known as the dictionary catalogue. It consists of an arrangement of author, subject, and (to a limited extent) title entries in a single alphabetical sequence, and is by far the most popular form. It is neither economical nor the most logical, but its convenience for ready reference compensates for these defects. It ordinarily answers questions 1, 2, 4, 5, 9, and can be made to answer questions 3, 7, 11, and 12—that is nine questions out of the twelve.
The two most common forms of catalogues are the dictionary and the classified. For many years much controversy has arisen respecting their comparative usefulness, and there is much to be said in favour of both, each having merits, as already shown, not possessed by the other. The late C. A. Cutter points out the advantages of the classified catalogue, thus: "One who is pursuing any general course of study finds brought together in one part of the catalogue most of the books he needs. He sees not merely books on the particular topic in which he is interested, but in immediate neighbourhood works on related topics, suggesting to him courses of investigation which he might otherwise overlook. He finds it an assistance to have all these works spread out before him, so that he can take a general survey of the ground before he chooses his route; and as he goes back, day after day, to his particular part of the catalogue he becomes familiar with it, turns to it at once, and uses it with ease. The same is true of the numerous class who are not making any investigation or pursuing any definite course of study, but are merely desultory readers. Their choice of books is usually made from certain kinds of literature or classes of subjects. Some like poetry or essays or plays [curiously he omits novels]; others like religious works, or philosophical works, or scientific works, not caring about the particular subject of the book so much as whether it be well-written or interesting. To these persons it is a convenience that their favourite kind of reading should all be contained in one or two parts of the catalogue, and freed from the confusing admixture of titles of a different sort. An alphabetical list of specific subjects is to them little more suggestive than an alphabetical list of authors. It is true that by following up all the references of a dictionary catalogue under Theology, for example, a man may construct for himself a list of the theological literature in the library; but to do this requires time and a mental effort, and it is the characteristic of the desultory reader that he is averse to mental effort. What is wanted by him and by the busy man when now and then he has the same object, is to find the titles from which he would select brought together within the compass of a few pages; few, that is, in comparison with the whole catalogue. It may be 500 pages, but 500 pages are better than 10,000. The classed catalogue is better suited also than any other to exhibit the richness of the library in particular departments."
Cutter, at the same time, proceeds to name some of the disadvantages of this style of catalogue. "A large part of the public are not pursuing general investigations. They want to find a particular book or a particular subject quickly; and the necessity of mastering a complex system before using the catalogue is an unwelcome delay or an absolute bar to its use." Then, again, there is the difficulty of want of agreement as to classifications. The simple remedy for such difficulty is an alphabetical index of all the subjects appearing in the catalogue, whereby an inquirer is directed to the particular part of the catalogue in which he will find books upon the subject or topic he wants. There are very few, if any, catalogues of the kind without indexes now, though in the early days they were seldom provided.