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Schellen and Roscoe, Mr. Lockyer has adopted an intermediate and independent course, and made an instructive volume of moderate size on questions at present most interesting in the theory and practice of spectroscopy. Treating but briefly of the construction of the spectroscope, which is so fully dealt with in the current works, he gives more attention to its uses and results in connection with problems that are now undergoing investigation. Chapter I. contains an excellent statement of the laws of wave-phenomena, that are at the foundation of the theory of spectrum analysis; and, as an example of the style and illustration of the book, as well as the interest of the exposition, we reproduce a portion of it in the present number of the Monthly. Chapter IV., treating of atoms and molecules, presents admirably the views at present held by chemists and physicists respecting the molecular constitution of matter in its relations to spectral phenomena. But the volume of Studies is mainly devoted to topics that concern amateurs and experimenters in the laboratory or the observatory. Besides the numerous woodcuts and the colored map of radiation and absorption spectra, Mr. Lockyer has introduced a series of photographic plates showing actual effects more accurately than would be possible with engravings; and this feature somewhat enhances the cost of the book.
The Epoch of the Mammoth, and the Apparition of Man upon the Earth. By James C. Southall, A. M., LL. D. With Illustrations. Philadelphia: J. B. Lippincott & Co. Pp. 430.
We cannot deal with this book better than to give here a portion of the able article devoted to it in the Saturday Review: