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UBLIC libraries usually divide their circulation into ten or a dozen broad classes and so report it. This division is interesting, but a subdivision of each class would be still more so. For instance the scientific man is interested to know that a given library circulates four per cent, of science, but he would be still more interested to know exactly what is included in 'science' and how much of the circulation is to be credited to each subclass. Those libraries that use the decimal classification of Melvil Dewey, which has been so generally adopted in this country, often report together as 'science' the classes 300 (sociology), 400 (philology) and 500 (natural science) and they exclude the applications of the last-named sciences, which are placed under useful arts. It is evident that in order to mean anything, a report of circulation should be more closely subdivided. This is true of many other classes, of course, as well as of science.

And yet a public library cannot systematically classify its circulation more closely than it does. To do so would involve a great amount of labor which would be more profitably expended in other directions. It is quite possible, however, to do this extra work for a short period and in a single class of literature and the result, even if partial and perhaps not typical, can not fail to interest those whose studies and work lie in the particular line of literature that is under investigation. Such a classification of the scientific circulation was made for this purpose in all of the circulating branches of the New York Public Library (11 in number at that time) during the month of May, 1901, with the result shown in the accompanying table. For purposes of comparison the circulation is accompanied by figures showing the number of volumes in each subclass, in each branch library.