A book describing the _Practical Methods of identifying Minerals in Rock Sections with the Microscope_[17] has been prepared by Mr. _L. McI. Luquer_ to ease the path of the student inexperienced in optical mineralogy by putting before him only those facts which are absolutely necessary for the proper recognition and identification of the minerals in thin sections. The microscopic and optical characters of the minerals are recorded in the order in which they would be observed with a petrographical microscope; when the sections are opaque, attention is called to the fact, and the characters are recorded as seen with incident light. The order of Rosenbusch, which is based on the symmetry of the crystalline form, is followed, with a few exceptions made for convenience. In an introductory chapter a practical elementary knowledge of optics as applied to optical mineralogy is attempted to be given, without going into an elaborate discussion of the subject. The petrographical microscope is described in detail. The application of it to the investigation of mineral characteristics is set forth in general and as to particular minerals. The preparation of sections and practical operations are described, and an optical scheme is appended, with the minerals grouped according to their common optical characters. [17] Minerals in Rock Sections; the Practical Method of identifying Minerals in Rock Sections with the Microscope. Especially arranged for Students in Scientific Schools. By Lea McIlvaine Luquer. New York: D. Van Nostrand Company. Pp. 117. Mr. _Herbert C. Whitaker's_ _Elements of Trigonometry_[18] is concise and of very convenient size for use. The introduction and the first five of the seven chapters have been prepared for the use of beginners. The other two chapters concern the properties of triangles and spherical triangles; an appendix presents the theory of logarithms; and a second appendix, treating of goniometry, complex quantities, and complex functions, has been added for students intending to take up work in higher departments of mathematics. For assisting a clearer understanding of the several processes, the author has sought to associate closely with every equation a definite meaning with reference to a diagram. Other characteristics of the book are the practical applications to mechanics, surveying, and other everyday problems; its many references to astronomical problems, and the constant use of geometry as a starting point and standard. [18] Elements of Trigonometry, with Tables. By Herbert C. Whitaker. Philadelphia: Eldredge & Brother. Pp. 200.