(1) PROF. E. H. CRAPPER'S book can be recommended to all desiring to obtain a thorough working knowledge of the everyday calculations which have to be made by alternating-current engineers. The lengthy experience the author has had in training electrical engineers has convinced him that the only way to master the subject is to acquire facility in solving the types of numerical problems which occur in practice. There are 232 examples in the book. The answers to all of them are given, and fifty are worked out in full. They are arranged in order of difficulty, and none of them make excessive demands on the knowledge or ability of the student. We have tested the numerical accuracy of the answers given to several of the problems with satisfactory results. (1) Arithmetic of Alternating Currents. By E. H. Crapper. Pp. vii + 208. (London: Whittaker and Co., 1915.) Price 2s. 6d. net. (2) Constant-voltage Transmission: a Discussion of the Use of Synchronous Motors for Eliminating Variation in Voltage in Electric Power Systems. By H. B. Dwight. Pp. vii + 115. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1915.) Price 5s. 6d. net. (3) Alternating-current Work: an Introductory Book for Engineers and Students. By W. P. Maycock. Pp. xxiii + 415. (London: Whittaker and Co., 1915.) Price 6s. net. (4) Experimental Electricity and Magnetism. By M. Finn. Pp. x + 436. (London: G. Bell and Sons, Ltd., 1915.) Price 4s. 6d.