By no means the least interesting and valuable feature of the book before us is the exposition of the historical development of the subject. We who are apt to look on the feminine scientist as a product of the last twenty years are reminded that there was at least one woman chemist of ability in the eighteenth century, Mrs. Fulhame, whose _Essay on Combustion_, published in 1774, emphasised the importance of the presence of moisture in gaseous reactions. Faraday, "the prince of experimenters," also worked on catalysis, and, in fact, originated the adsorbtion theory of the process, which attributes the action to the extended compressed film formed at the surface of a porous solid. It is not only in the chapter expressly devoted to the early history that we find an account of the original workers; the advances made by them receive recognition throughout the book in connection with the branches in which they experimented. The treatment of the various theories of catalysis--the intermediate compound, the adsorbtion, electrochemical, and radiant energy theory--might have been extended with advantage. The mathematical exposition of the adsorbtion theory is one of the weakest things in the book, and McLewis's work is not very clearly handled. The difficulties of giving an adequate summary of this part of the subject are undoubted, but the need of it is so marked that we regret that the authors have not spent more energy on the task. This is not the place to deal in detail with the account of the practical applications of catalysis, which is excellently done and includes the most recent work, some of it, such as Partington's improvements in oxidising ammonia, only made public last year. The use of catalysts in, to take a few examples at random, surface combustion, the hardening of oils by hydrogenation (used so extensively in margarine making), the fixation of nitrogen, and electrolysis is well described, and there is a good chapter on ferments and enzymes, and another on the Grignard reagent. Omissions may be noted here and there, but the book is not, of course, intended to give detailed instructions to the commercial chemist. Rather, we believe, is it meant to supply to chemists in general, and even to the lay reader, an idea of the nature of the process of catalysis, which is becoming more important every day, and the extent of its applications, with sufficient detail to make the reactions clear, as far as they are at present understood. As a general exposition of the subject the book is really needed, and will undoubtedly find a place on the shelves of all who follow the advances of science.