Page:Popular Science Monthly Volume 16.djvu/444

424 the valley of the Zibagy and tributary streams, in the sands, in pot-holes, and in gravel-banks. The diamonds appear to have been washed out of the Devonian sandstone of that region, but the author thinks they were previously derived from metamorphic rocks, and deposited in the sands: which afterward went to form these sandstones. That they did not originate in the latter is proved, he thinks, by the fact that it contains no traces of metamorphism or of crystallization.

of some maturity of mind, say a young medical student, who knew nothing whatever of the subject, might derive advantage from reading over this brief introduction; but it is not a "First Step" in any sense that it could be used in a primary school to start young beginners. It contains a very readable summary of chemical principles, but they are presented in the elaborated thought and technical language of the developed science.

has here hit upon an excellent idea, and has carried it out very successfully. There was room for a popular book on common things much more full than the current "familiar science" manuals. A great deal of miscellaneous information on ordinary objects and subjects has been collated and digested in alphabetical order convenient for reference, and the editor is right in calling attention at the outset to the need of encouraging in the young the practice of consulting works of reference. The volume will be found most useful in families, as both the knowledge it imparts and the form of its presentation are well suited to satisfy the curiosity of young minds. A good deal of information is given about the common sciences, such as astronomy, chemistry, physics, natural history, and physiology, and about heat, light, air, electricity, and the parts and operations of the human system. There is much about the modes of manufacture of common articles, and the natural history of the more familiar and important animals and plants is fully presented. The book is compiled with judgment, Mr. Champlin having undergone his apprenticeship at this kind of work on the "American Cyclopædia." We are glad to notice that Holt puts the book at a quite reasonable price.

claims to be an elementary book for students to begin with, but the beginning must be in the old lecture-room form of instruction. The author says: "It is not enough, as every teacher knows, to exhibit experiments before a class, unless they are made subservient to explain the theory of the science, and to place it on a sound basis. All theoretical explanations should be based upon experiments which fix it upon the memory. This is the plan which I have laid down for my guidance." As might therefore be expected, the book is filled with illustrations and descriptions of lecture room experiments, and the usually accompanying explanations and information. It is clear, accurate, and well executed.

anonymous writer, thinking Mr. Mallock's book worth answering, has replied to his arguments very fully and ably in this volume. The book is written from the Positivist point of view, in the more special sense of the term. By Positivism, Mr. Mallock means those later tendencies and theories of science which bear upon the higher questions of religion, morality, and polity, and as illustrated in the writings of such thinkers as Clifford, Huxley, Tyndall, and Mill, but Mr. Mallock's critic rather means by "Positivism" the doctrines of Comte; and this reply is chiefly interesting as dealing with Mr. Mallock's questions from that point of view.