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to this feature of the work, because the current notion of the unattractiveness of scientific writers is often made an excuse for neglecting valuable scientific books, and we wish to apprise those who are addicted to this habit that the excuse is not valid in the case of the present work.

Chemical and Geological Essays. By Thomas Sterry Hunt, LL. D. 489 pages. Price, $3.00. J. R. Osgood & Co.

Among the multitude of compilations and digests upon scientific subjects, which have been latterly put forth on both sides of the Atlantic, by men whose names lend no weight to their work, we welcome this substantial volume by one who has devoted his life to the original and independent study of the subjects with which it deals, and whose high reputation, and the honors he has received from learned societies both at home and abroad, give the best assurance of the valuable character of his labors. Dr. Hunt has done the public an excellent service, in collecting and republishing his chief scientific memoirs. His volume, indeed, was wanted. We have many and excellent text-books of geology and text-books of chemistry, but something like a comprehensive text-book of the relations of these two sciences was a desideratum in our scientific literature which this work will go far toward supplying. For, although it was prepared for no such purpose, and although its papers were produced at different times in the course of a life devoted to research, and of course bear the stamp of the author's views, yet its statements of facts are to be thoroughly trusted, while their theoretic interpretations are so presented as to give us the latest views that science has reached respecting them. The volume is both a representation of the present state of knowledge upon chemical geology and of the growth of that knowledge during the past generation. In no field has there been greater activity of investigation, and, while Dr. Hunt develops the views to which his own studies have led him, he gives us at the same time the opinions entertained by others, or previously accepted, so that the reader is well instructed upon the subject, and is able to form an intelligent judgment for himself. The following passage from his preface will give an idea of the extent of the topics considered. The author's "researches and his conclusions at to the chemistry of the air, the waters, and the earth, in past and present times; the origin of limestones, dolomites, and gypsums, of mineral waters, petroleum, and metalliferous deposits, the generation of silicated minerals, the theory of mechanical and chemical sediments, and the origin of crystalline rocks and vein-stones, including erupted rocks and volcanic products, cover nearly all the more important points in chemical geology. They have, moreover, been by him connected with the hypothesis of a cooling globe, and with certain views of geological dynamics, making together a complete scheme of chemical and physical geology." Since the appearance of Bischoff's treatise on chemical geology, twenty years ago (it was never republished in this country, and if we are not mistaken it is now out of print), we have met with no book that so fully covers the ground as this collection of essays. It will be valuable for reference to the students of economical geology, and interesting to general readers who care to understand any thing about the great agencies of Nature which have produced, and are still carrying on, the changes in the crust of the earth. It will at once take its place in the libraries of scientific men, and should be introduced for reference into all schools where chemical and geological science is studied.

The Principles of Sociology. By Herbert Spencer. Part I. Eighty pages. Price, 50 cents. Published quarterly. $2 a year. D. Appleton & Co.

After an interval of some delay, Mr. Spencer resumes the course of his philosophical serial, and has now entered upon what will generally be regarded as its most important part. There has been much impatience, with many, that he has been so slow in reaching the practical and pressing problems of social science which he was expected to handle with originality and power; and readers have complained of the prolonged discussions in biology and physiology which seemed to have nothing more than a speculative importance. But we already begin to see that Mr. Spencer understood what he was about in his thorough elab-