THE work of revising the excellent treatise of the late Mr. W. G. McMillan has, on the whole, been admirably done by Mr. Cooper, although there still remain a few slight errors in the body of the work which might have been corrected. For example, it is manifestly an error to recommend for nickel deposition a solution of 8 pounds of nickel ammonium sulphate per gallon (p. 220). Some of the recent developments in the practice of electroplating might have been given more attention, such as electrolytic methods of cleaning which of late years seem to have come into favour; and the important uses of the sand blast are still, as in former editions, almost ignored. It is, however, impossible to deal adequately within the limits of a volume of reasonable size, with all the aspects of so wide a subject, and the general excellence of the treatise in its revised and enlarged form elicits warm approval. A Treatise on Electro-Metallurgy: Embracing the Application of Electrolysis to the Plating, Depositing, Smelting, and Refining of Various Metals, and to the Reproduction of Printing Surfaces and Art-work, etc. By W. G. McMillan. Third edition, revised and enlarged. Revised by W. R. Cooper. Pp. xv + 425. (London: Charles Griffin and Co., Ltd., 1910.) Price 12s. 6d. net.