The chief difficulty with most systems for distributing the books in a library appears to lie in the attempt to apply scientific minuteness in a region where it is largely inapplicable. One can divide and sub-divide the literature of any science indefinitely, in a list of subjects, but such exhaustive sub-divisions can never be made among the books on the shelves. Here, for example, is a "Treatise on diseases of the heart and lungs." This falls naturally into its two places in the subject catalogue, the one under "Heart," and the second under "Lungs;" but the attempt to classify it on the shelves must fail, as regards half its contents. You cannot tear the book to pieces to satisfy logical classification. Thousands of similar cases will occur, where the same book treats of several subjects. Nearly all periodicals and transactions of societies of every kind refuse to be classified, though they can be catalogued perfectly on paper by analysing their contents. To bring all the resources of the library on any subject together on the shelves is clearly impossible. They must be assembled for readers from various sections of the library, where the rule of analogy or of superior convenience has placed them. What is termed close classification, it will be found, fails by attempting too much. One of the chief obstacles to its general use is that it involves a too complicated notation. The many letters and figures that indicate position on the shelves are difficult to remember in the direct ratio of their number. The more minute the classification, the more signs of location are required. When they become very numerous, in any system of classification, the system breaks down by its own weight. Library attendants consume an undue amount of time in learning it, and library cataloguers and classifiers in affixing the requisite signs of designation to the labels, the shelves, and the catalogues. Memory, too, is unduly taxed to apply the system. While a superior memory may be found equal to any task imposed upon it, average memories are not so fortunate. The expert librarian, in whose accomplished head the whole world of science and literature lies cooerdinated, so that he can apply his classification unerringly to all the books in a vast library, must not presume that unskilled assistants can do the same.