Page:Popular Science Monthly Volume 47.djvu/870

852 chemistry since the German edition of this work appeared, and the second being a valuable synchronistic table of chemical periodicals. The index is divided in the clumsy German fashion.

need be added to the title of this book to indicate its field, and the authors claim no originality in the matter presented, except as to the construction of the equations for magnetic leakage, for the heating of dynamos, or the E. M. F. of alternators. "Yet we do claim," they say, "a certain novelty in our method of treatment by which these facts are presented. It has seemed to us that a systematic and methodical analysis of dynamos—of the causes and reasons why they have assumed their present shape—if only it be complete and accurate, so far as its scope extends, would still be sufficiently novel to merit attention. Starting with a simple inductor cutting the lines of a magnetic field, such an analysis would gradually evolve in natural sequence the various combinations of inductors which constitute the windings of armatures and the typical forms which the complete machine is thence compelled to take, until, finally, the whole should culminate in the description of actual machines as manufactured, and the practical design of one or more dynamos for given outputs. This scheme we have endeavored to carry out." The authors have taken pains to unite practice and theory in this treatise and to avoid mathematics and technicalities that were avoidable. There are one hundred and ninety illustrations, including cuts of a number of typical dynamos.

book has been written for college students, and assumes some elementary knowledge of chemistry in those who are to use it. The author first gives a short chapter to the atomic theory, which he holds should not be presented in an elementary course, and then proceeds to describe the elements and their inorganic compounds. Oxygen is the first element described, hydrogen, the halogens, and the oxygen family following in succession. "In discussing chemical changes," Prof. Freer says; he has "endeavored to present the various topics, not as a series of isolated facts, but as so connected, the one with the other, that there is scarcely any one of the numerous phenomena which are mentioned in this work which does not find its analogon in some other portion of the field of chemical study. The attempt has been made especially to call attention to the influence exerted by the nature of the elements which make up a chemical compound upon the character of that compound itself." In his treatment of the latter subject he is aware that he may have been led into some speculation, but bespeaks at least a hearing for the new arguments he has ventured upon. His views on valence and the use of structural formulæ are conservative. In the application of physical methods in the study of chemistry he has followed Ostwald and Lothar Meyer, and in regard to the double halides, fluosilicic acid, and similarly constituted bodies he has adopted the views advocated by Prof. Remsen. There is an appendix of some forty pages of laboratory notes, which is "not intended as a laboratory manual, but mainly as a guide to both teacher and pupil in compiling a list of experiments."

book, the author says, is a record of a traveler's impressions of the great monuments of France, published in the hope that it may bring others to visit them. "It is easy for the student to get accurate information about them; but nevertheless it may be of some use to tell what effect they produce upon one who does not wish to study deeply into all their history and the minute details of the building of them, but who does love their beauty and cares about the place they hold in the history of the French people." We read the systematic accounts of these things and get vague ideas about them as something shadowy and far distant; then, as a lady remarked on seeing the antiquities