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.