AMONG the many indications of the increasing interest which technical education, in its widest extent, now calls forth, one of the most conspicuous is the production of manuals and text-books on the various subjects with which it deals. Amongst these there is none which is more important than Applied Mechanics, and, at the same time, we may add that there is none which has been more in need of a good elementary textbook. The great works on the subject by Rankine and Moseley are not adapted for elementary teaching, involving mathematical processes beyond the power of a beginner, and thus it has come to pass that a country renowned for its engineering triumphs and for the excellence of many treatises dealing with the practical applications of applied mechanics, has hitherto possessed no book devoted to an exposition of its principles and suitable for educational purposes. Those persons, therefore, who are familiar with Prof. Cotterill's work on the Steam-Engine will have looked forward with much interest to the publication of his long-advertised book on “Applied Mechanics.” Its recent appearance we venture to think has in no sense disappointed their expectation, for it bears on every page evidence that its author has not only studied and become intimately acquainted with his subject, but that he possesses the rare faculty of having learned by experience in teaching, the best way of presenting a subject so as to diminish its difficulties and make rough places smooth for the footsteps of the beginner. By assuming a knowledge on the part of the reader of the elements of theoretical mechanics he has been enabled to devote the whole of this large volume to the exposition of the more complicated science, in which the principles of the former are applied to the problems of construction presented to the architect and the engineer. The treatise is strictly elementary in its methods, the mathematics used being, almost without exception, of the simplest kind, and many results, which have usually been obtained by complicated investigations, are here arrived at by neat and elegant simple processes. The style of reasoning adopted is also very successful, being neither too diffuse, nor, on the other hand, so much compressed as to puzzle and dishearten the beginner by gaps in the reasoning which his mental capacity is not able to bridge. This is particularly evident in the earlier parts of the book. Towards the end, in the section on Hydraulics and Pneumatics, we think that sufficient fulness of explanation has hardly been furnished, in dealing with the application of the principles of Energy, Momentum and Moment of Momentum, to Fluids, and especially in the case of Hydraulic Motors, to enable the student to grasp the subject without a frequent reference to some of the text-books which the author names. Applied Mechanics: an Elementary General Introduction to the Theory of Structures and Machines. By James H. Cotterill. (London: Macmillan and Co., 1884.)