Such is, in its main features, the system of book-press arrangement which I have undertaken to describe. I have no fear but that it will be pronounced in essentials logical and philosophical. It has undoubtedly proved eminently convenient in practice. That it should be open to revision on some points is inevitable from the nature of things, and from two circumstances more especially—its gradual development as subject after subject was added to the library, and the degree in which it represents the idiosyncrasy of a single mind. Some minor oversights must be admitted. Geology, for example, should unquestionably have preceded Botany. I venture more extensive criticisms with hesitation, yet I cannot help remarking that I perceive no valid reason for the severance of so manifest a branch of History as Biography from the parent stem by the intrusion of the entire department of Geography; while it appears to me that the Useful Arts would have formed, through Domestic Economy, a more natural sequel to Medicine than Fine Art, and in arranging the latter department I should have assigned the last instead of the first place to Archæology and its allied subjects. Forensic Medicine might also have been conveniently placed at the _end_ of Law, to connect that subject with Natural Science. I should further feel much inclined to form a class for Encyclopædias immediately after Philology; both because dictionaries of general knowledge seem legitimate successors to dictionaries of languages, and that the end of the classification might be answerable in dignity to the beginning. I am aware how much room for diversity of opinion may exist on these and similar points. On a more serious defect there can be no difference of opinion, but it is a defect inherent in all finite things. In an ideal classification by book-press one separate press, at least, would be provided for each subject, however minute. But an ideal library would also have room for each subdivision. We cannot have the ideal classification without the ideal library, and, although I hazard nothing in saying that, thanks to the genius of the designer, Sir Anthony Panizzi, economy of space in the new buildings of the Museum has been carried to the utmost extent conceivable, space is still insufficient to provide a distinct niche for every well-marked division of a subject. Upwards of five hundred such subdivisions are provided for; nevertheless this large number is not exhaustive. Without such an exhaustive distribution, the actual classification on the shelves, which is all I have undertaken to describe here, can never be conterminous with the ideal classification of the study. If, however, the Museum library has been unable to achieve an infinity of space, it has secured a practically indefinite numerical expansiveness by the elastic system referred to in our President's address, in further illustration of which I may be allowed a few words. On the removal of the books from Montague