SHORTER NOTICES 319 a topic whose inherent possibilities are too frequently overlooked. It remains as a particularly pleasant memory of the flight ! The sixth and last chapter, with its discussions of plane collineations and correlations, quadratic transformations, linear and tetrahedral complexes of lines, and space collineations, brings the book to a close. This chapter is rather sketchy, perhaps by necessity, but it does round out the whole very nicely. In general, then, the book is not for

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... he beginner. It is a resumé of a portion of the field of projective geometry, intended for a reader who has had some previous acquaintance with the details. The approach, one might say, is in the manner of Reye, and there is little of the concern for logical detail usually so evident in the postulational developments of the present day. However, although some may raise objection on the ground that it is not in the modern fashion, it does present quantity in a small package and does it well. B. C. PATTERSON Quantentheorie. By Clemens Schaefer. (Einführung in die theoretische Physik, vol. 3, part 2.) Berlin and Leipzig, de Gruyter, 1937. 7+510 pp.