PREFACE TO THE FIRST EDITION. A short course of lectures on Aero Engines was given by the author at the Northampton Polytechnic Institute during 1914. On the suggestion of Mr Charles E. Larard, M.Inst.C.E., M,I.M.E., Head of the Engineering Department, the matter contained in these lectures - necessarily somewhat rearranged and largely extended-is now issued in book form, in the hope that it may be found of assistance to a wider circle of readers.

The engines are classified as Horizontal, Radial, Diagonal, Vertical, and Rotary; after some preliminary theoretical matter, one or two typical engines of each of these five classes are illustrated and described in some detail. This is thought to be preferable to the alternative of giving very brief references to a larger number of the exceedingly numerous aero engines that have already appeared.

PUBLISHERS' NOTE TO THE EIGHTH EDITION. Seven large editions of this book have been called for in rapid succession, and it is very gratifying to both Author and Publishers that an eighth edition is now required. As up-to-date as war-time conditions permit, it has proved a most valuable theoretical basis for practical training; and being both trustworthy and exhaus-tive, Government Departments have made large use of it, whilst designers, students, and all interested in aviation have found it worthy of close consideration. March 1917.