The designation of book sizes is a vexed question in catalogues. The generally used descriptions of size, from folio down to 48mo. signify no accurate measurement whatever, the same book being described by different catalogues as 12mo. 8vo, crown 8vo. &c., according to fancy; while the same cataloguer who describes a volume as octavo to-day, is very likely to call it a duodecimo to-morrow. Library catalogues are full of these heterogeneous descriptions, and the size-notation is the _bete noir_ of the veteran bibliographer, and the despair of the infant librarian. Yet it is probable that the question has excited a discussion out of all proportion to its importance. Of what consequence is the size of a book to any one, except to the searcher who has to find it on the shelves? While the matter has been much exaggerated, some concert or uniformity in describing the sizes of books is highly desirable. A Committee of the American Library Association agreed to a size-notation, figured below, adopting the metric system as the standard, to which we add the approximate equivalents in inches. _Centimetres_ _Size_ _outside_ _Sizes._ _abbreviations._ _height._ _Inches._ Folio, F deg.. F 40 16 Quarto, 4 deg.. Q 30 12 Octavo, 8 deg.. O 25 10 Duodecimo, 12 deg.. D 20 8 Sixteen mo., 16 deg.. S 17.5 7 Twenty-four mo., 24 deg.. T 15 6 Thirty-two mo., 32 deg.. Tt 12.3 5 Forty-eight mo., 48 deg.. Fe 10 4 It will be understood that the figure against each size indicated represents the maximum measure: _e. g._ a volume is octavo when above 20 and below 25 centimetres (8 to 10 inches high).