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570 NEW BOOKS. on the title-page which may tempt readers. It must be said, too, that the writer, if he has caught Mr. Robertson's spirit, has also caught some- thing of his charm of style. Polemical from end to end, his book is distinctly entertaining to those who know its originals. Hypnotism and its Application to Practical Medicine. By 0. G. WETTERSTRAXD. Translated from the German edition by H. G. PETERSEX. Medical Letters on Hypno-suggestion. By H. G. PETERSEN. London and New York : G. P. Putnam's Sons, 1897. Pp. xviL, 117 + 48. Dr. Wetterstrand is a follower of Liebeault, and therefore a member of the ' school ' which includes Bernheim, Forel, etc. His book, which has already appeared in Swedish, German and Russian, consists of re- ports of cases in which he has employed hypnosis for therapeutic purposes, together with a brief introduction on the hypnotic state and an equally brief conclusion on the value of suggestive therapeutics hi general. Its empirical and non-speculative character makes it a welcome and im- portant contribution to hypnotic literature. The translation is accurate and readable. Dr. Petersen, an enthusiastic adherent of the Nancy doctrines, writes sensibly on practical questions, but shows little grasp of his subject when he ventures on the ground of psychology and metaphysics. His Letters deal with the practical teachings of the use of psychology hi medicine, with suggestive treatment in reform work, with post-hypnotic responsibility and with the question of music v. sermons for the insane. A History of Elementary Mathematics : with Hints on Methods of Teaching. By F. CAJORI. New York and London : The Macrnillan Co., 1896. Pp. viii., 304. This book has a two-fold value for the psychologist. The history of any science, rightly told, constitutes a piece of social psychology ; and mathematics has a special claim upon the psychological attention, in virtue of its unique position among the sciences. Prof. Cajori's work, however, has more than this general value. By its wealth of clearly worded illustration it gives us many glimpses of the way in which the human mind actually set about its task in the first days of mathematical thinking. If the reader is unfamiliar with the treatment of fractions in the Ahmes papyrus, let him procure this History and he will receive his reward. Prof. Cajori is already favourably known by his larger History of Mathematics (1895). The present volume, which gives many references to the sources and is furnished with a good index, has been well received by the technical journals ; so that the layman may read with faith. The book opens with a brief discussion of number-systems and numerals ; and thereafter falls into three parts, dealing with the arithmetic, algebra,, trigonometry and geometry of antiquity, the middle ages and modern times respectively. Ethics of J. S. Mill ; edited with Introductory Essays. By CHARLES DOUGLAS, M.A., D.Sc., Lecturer and Assistant in Moral Philosophy in the University of Edinburgh. Edinburgh and London : William Blackwood & Sons, 1897. Pp. cxxvi., 233. The general scope of this work is well indicated in the Preface. "It has been very usual for students to confine their reading of Mill's ethics to