Definition.—Classification consists of putting like things together. We do this every day, and the classification of books is only one special phase of this general process. Thus, a man who owns a hardware store does not place his goods helter skelter,—a stove, a box of nails, some saws and then a furnace, but he runs over his stock and classifies it, putting stoves in one place, nails in another. By this classification he gains two things: first, he can find any one thing he wants more quickly; secondly, he can tell how much of any one article he has on hand and so decide whether he must lay in a new supply. Likewise, the zoologist classifies all members of the animal kingdom, so that he can learn what the different kinds of animals are and study the relationship between them. Without the help afforded by classification he would be overwhelmed by the immense number of facts brought before him and without the aid of classification he would never have known of evolution, the guiding star of modern investigation.

First Principles.—In our every-day life we lose much time hunting for things for which we have no definite place. We have put them in the place which was most convenient for us at the moment when we put them away. Think for yourself how it is with your knowledge. From observation, from conversation, from reading, you learn a little about many subjects like electricity, botany, astronomy or politics, but in this desultory way you do not learn very much about any one of these subjects. Therefore you do not feel any special need of classifying your information, but when you take up any of these subjects and pursue it seriously you learn thousands of facts and relations, and then is the time that you feel the need of some plan of arrangement of your knowledge.

Private vs. Institutional Libraries.—One has the same experience in regard to books. A person having a library of from fifty to three hundred books does not feel the need of classifying them. The ordinary arrangement is based upon size, color or convenience. The books in the average house are so placed as to look their best. The classification, as far as it exists, is an esthetic one. The owner knows the exact appearance of every volume in his library and when he wants Longfellow’s poems he can tell at a glance where it is. In a small private library there is no occasion for all the history being in one place or all the poems in another. As the library grows, the esthetic principle of classification can be followed until the owner can no longer readily remember how each book looks.

But our institutional libraries contain so many books that the librarian cannot know them in the same way that he can the books in his own private library and consequently he has to study the question of classification and devise a method by which not only he, but his assistants and also such readers as have access to the books, can readily find them as wanted. Classification, the putting of like things together, would, therefore, mean in a large library, putting histories together in one place, the medical books together in another place, and so with all other distinctive subjects. Each of these large classes will, however, have to be subdivided. Thus, histories of Greece are put together in one place, histories of Rome in another, histories of the United States in still another. The subdivision in the larger libraries is carried still farther and books on the period of the discovery of America are put first, followed by books on the Colonial period of the United States, the Revolutionary War, etc. United States history, if well represented, is classified geographically. This process of subdivision into separate groups of books on each state can be carried still farther if necessary.

Advantages of Classification.—The following questions may arise: What advantages come from the classification, and who are benefited? The advantages come to those having access to the books. If one goes to a library to get a volume by Arnold Bennett it makes no difference to the individual whether the library is classified or not if he cannot go to the shelves and pick out the book for himself. Likewise, if he wants Young’s Astronomy he will probably get the book more quickly if he asks the attendant to get it than if he tries to get it himself, supposing he does have access to the shelves. But the time when the reader gets the most help from the classification is when he wants to examine a number of books on astronomy and can go to the shelves and find the books on that subject all in one place. Then he can easily find what different writers have to say about the habitability of Mars or he can find what book appeals to him as being the most interesting and can borrow it for home use. Any investigator finds access to the shelves of a well classified library an immense help.

An Aid to the Librarian.—Another person who is greatly benefited by classification is the librarian, and it is just as important that he be helped as that the reader be helped. He is, however, helped in a different way. He knows what the system of classification in use in the library is and with the outlines of this scheme in mind he goes through the library and finds out where it is strong and where it is weak and can plan future purchases accordingly. If, for example, he finds on the shelves little of value on photography he will make a note of it and buy more books on that subject when funds are available. If he finds that there is an undue supply of travel on hand, he will note that also and buy fewer books in that class in the future. Without the help of classification the librarian would overlook many such irregularities. In an unclassified library they would be discovered only through a long and tedious investigation. His only recourse would be the catalog and that is not so well adapted to answer such questions.

Basis of Classification.—The next question is, what shall be the basis of classification. It is obvious that this basis should be sought in the character of the books themselves and should be applied with constant reference to the reader and his needs. In regard to the first point, character of the books, we know that books have been written on all kinds of subjects,—religion, law, history, medicine, etc. and that those subjects form the only rational basis for classification. A classification based on these distinctions is the only one that helps the reader. If a man comes to the library to investigate a particular point in medicine, it is clear that it will help him if he finds all the medical books together rather than all the books grouped according to their date of purchase by the library.

Present Tendency.—Many schemes have been devised for the classification of books, some very simple, others extremely elaborate. The present tendency is to adopt the more elaborate classification. Formerly most libraries were not classified at all, but the books were arranged in the order in which they were received, the only grouping of the books being in such cases one based on size,—folios in one place, quartos in another, in order to save shelf room. Assuming that the books in the library were numbered according to the date of their accession from one up to, say, twenty thousand, it is clear that the reader could find a book by a particular writer quickly enough by looking up its number in the catalog, but if he had wished to consult thirty books on one subject, it would be a very tedious operation and most readers would not take the time for it.

Simple forms of Classification.—The most common plan in English libraries is a modification of this scheme. The books are divided into about ten classes and the books in each class are arranged in the order in which they are received. The classes are distinguished by capital letters. An example said to be very common in England, is as follows.

As an illustration of the way a book is marked in this scheme, B 2574 might be Green’s “History of the English people.” This book is marked B. because it is a history. It is marked 2574 because there were already 2573 books in this class at the time this book was added. This mark, B 2574, is a very simple one and to that extent satisfactory. The scheme is a great advance over the preceding one, because it brings the books of a kind together. Since there are ten classes in this scheme, it is evident that if a reader wishes to see all the books on one subject he will have to examine only one-tenth of the library instead of the whole of it, but even this is not felt to be minute enough. If the library contains 200,000 volumes one class would contain, on the average, 20,000 volumes, which is altogether too great a collection to search through. If Green’s “History of the English people” were marked B 2574, the next book might be Robinson’s “History of Peru,” marked B 2575, which is of course a very different subject. The case is still worse in class E, which includes fine arts, useful arts and all the sciences, so that a book on chemistry might stand between a book on medicine and one on Raphael. This would not satisfy the reading public of to-day,—nor the modern librarian. The classes F, fiction, and J, juvenile, are not so bad; there is not so great a difference between the books in these classes. They are used more by people seeking recreation, rather than by those looking for definite titles. Jacob Abbott wrote some two hundred juvenile books and many of these might be scattered among the large class J. In class F, fiction, the English, French, and German authors would all be thrown together. This would be a disadvantage for any one desiring to read along a particular line.

Open vs. Close Classification.—The question of open vs. close classification is an important one. By open classification we mean one without minute subdivisions. An illustration of open classification is the scheme of ten classes described above. As an extreme case of open classification mention may be made of the theological library in which only two classes were used, the one class containing the books that were sound in their theology, the other the books that were unsound.

At the present time the tendency is towards close classification. It is a necessity in large libraries and an advantage in small ones. In this country the two great authorities on classification are Charles A. Cutter and Melvil Dewey. Both have devised and published schemes of classification which are generally recognized as having many excellent features. In both schemes the classification admits of very minute subdivisions. Dewey says that if the library has only one book on a certain minute subject, that book ought to be put in its own special class. It does not matter if there is no other book in the class. No one can fully understand what is meant by close classification until he has had considerable experience in classifying books. You can pick up the printed scheme of classification and run your eye over the numbers, but you will get comparatively little from them until you try to apply them.

Minute Bibliographical Classification.—The following is a very important distinction in regard to close classification which should be carefully noted. It is one thing to classify books, but it is quite a different thing to classify articles in magazines for the bibliography of a subject. Magazine articles may be classified far more minutely than books can be. Take, for example, the Bibliographia Geologica, in which references are made to articles in geological magazines and publications of geological societies. Here the articles are classified according to Dewey. Dewey’s class 551 means physical geology. In this bibliography there is a particular article marked 551.795,513,111,044. That is to say the general subject of physical geology is subdivided in one-trillionth parts and this article is assigned to one of those parts. If one should apply for a library position and be told that he should have to classify the books as closely as this, he would probably never get the position. If he were given this article to classify, he would just as likely as not put it ten billion points out of the way. As a matter of fact, this bibliography is compiled by a number of experts in geology. There are similar bibliographies of botany, zoology and other natural sciences, all minutely classified and all compiled by experts.

The reason that books cannot be as closely classified as magazine articles is that they generally deal with broader topics. In the average library it does not pay to classify books more minutely than is warranted by the general run of books in the class in which these books are to be assigned. In this regard, a distinction must be made between libraries. The Library of Congress has devised a classification of its own which is very minute, and a number of classifiers are employed to look after the different fields in which they are more or less expert. In this way, classification can be carried to the extreme limit of closeness. Nothing keeps one more modest than classifying, for one is continually brought face to face with things that one does not know, and so many things of which one knows so little.

The Dewey Decimal Classification. The decimal classification is used in this country and in Europe. It is suitable for both large and small collections of books and for indexing. In many schemes of classification letters are used to denote the classes, in others a combination of letters and figures. Dewey uses only figures.

Dewey developed his system in 1873 and published it in 1876. Numbers of three figures were used to denote the classes. Since then it has been found desirable to subdivide much more minutely and this has been done with increasing minuteness in the seven editions that have followed the one of 1876. A general outline of Dewey is here given.

Each of these is divided into ten sections, e. g.

Each of these is divided into ten sections, e. g.

These sections are still further subdivided until the requisite degree of minuteness is reached. The system has various mnemonic features which are helpful. Every figure has a meaning. An alphabetical list of all these meanings is appended to the classification. Thus after the word Hydraulics is 532, showing where to look in the classification for this subject. All books on hydraulics receive the number 532 and are together on the shelves. This fact illustrates one great advantage of the Dewey system, that as the library grows the new books can be placed with the corresponding old ones without re-marking the old ones, while in the fixed location system the books are marked to certain localities, and when moved by reason of growth of the library have to be re-marked. This re-marking includes not only the books but also the cards referring to the books. The re-marking is very costly and very unsatisfactory. In Dewey’s system the books in any one class are arranged according to some method. In most classes an alphabetical arrangement by the names of the authors is simplest and best. In scientific classes some librarians prefer the chronological arrangement. In any case it should be clear and simple.

Relative Location.—“With a movable location all new books fall at once into their proper places like the cards which are added to a card catalog, and the new-comers push the other books along on the shelf, just as new cards push the others along in the drawer. The consequence is that a book which is here to-day may be on the next shelf in a month or in the next alcove in a year; and the local memory, which is a great help in finding books quickly is disturbed. The only remedy that I can see for this is to substitute a subject memory for a local memory, to get a habit of thinking of a book as belonging to a certain class instead of as on a certain shelf (a much more rational memory, by the way), and then to make it very easy to find the classes. This last is not hard to accomplish. A class memory can be cultivated and may be assisted by local memory which will find books by their position relative to other books, instead of by their position relative to alcoves and shelves, or doors and windows.”—C. A. Cutter.