A FULL discussion is given in this book of the practical theory of the induction motor and of several of the main types of alternating current motors. The author also gives a historical account of the invention of the induction motor and of the development of its theory. He attributes the invention to Nikola Tesla in 1888. In England it is generally attributed to Ferraris, who certainly made an induction motor, the rotating part of which was a solid copper cylinder, in the autumn of 1885. In this connection also, Baily has some claim to be called the inventor, as he showed a disc revolving in a rotating magnetic field to the Physical Society of London in June 1879. Tesla and the Westinghouse Co., however, were the first to make a motor similar to those used to-day. They had great difficulties to contend with, as the standard frequency of alternating current supply in America in 1888 was 135. The Induction Motor and other Alternating Current Motors. By B. A. Behrend. Second edition, revised and enlarged. Pp. xxiii + 272. (New York and London: McGraw-Hill Book Company, Inc., 1921.) 24s. net.