UP to the present time the study of problems relating to aeroplanes and airships has conspicuously failed to attract the attention of our leading mathematicians and mathematical physicists. This is the more surprising in view of the important part that has been played in the past, and is still being played, by methods of mathematical analysis in systematising and elucidating our knowledge of electric phenomena. A book by so trustworthy a mathematician as Sir G. Greenhill should prove of great value in clearing up the misunderstandings which have so frequently arisen as to the meaning and use (or misuse) of formulae in connection with aeronautics. The Dynamics of Mechanical Flight. Lectures delivered at the Imperial College of Science and Technology, March, 1910 and 1911. By Sir G. Greenhill. Pp. iii + 121. (London: Constable and Co., Ltd., 1912.) Price 8s. 6d. net.