The Theory of Light. By Thomas Preston, M.A. (Macmillan and
Co.)—Mr. Preston tells us that this book is to meet the wants of junior students, but may be read by those who desire more exhaustive treatment. Certainly the size of the volume, the thoroughness of it, and the working out of some of the problems, will make it most acceptable to the advanced student. Mr. Preston has devoted himself chiefly to the theories and the experiments of different investigators, and their comparative value. The most interesting portion of the volume is that devoted to "The Polarisation of Light," which he describes, indeed, systematically and thoroughly. We commend The Theory of Light, for it is a decidedly clear, straightforward, and exact treatise, and has, moreover, an interest of its own.