TO a large extent this book is a product of the advent of aeronautics, and its preparation would not have been possible fifteen years ago. The author passed through the period during which no accurate means existed of measuring the velocity of fluids, and was intimately associated with the history of the needs of such methods as he describes. At the present moment, the calibration of anemometers depends on a solitary series of absolute measurements at the National Physical Laboratory, part of which was conducted by the author himself. The work of Stanton on wind pressure in 1903 was the first contribution to the production of the tube anemometer illustrated on p. 13; its establishment as a satisfactory standard followed the formation of an Aeronautics Department, and the development then reached the stage at which a skilled workman can reproduce the instrument so accurately as to give speed within one per cent, without special test. The Measurement of Fluid Velocity and Pressure. J. R. Pannell. R. A. Frazer. Pp. vii + 135. (London: E. Arnold and Co., 1924.) 10s. 6d. net.