THE POPULAR SCIENCE MONTHLY. 



ical 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. 



The Dynamo: Its Theory, Design, and 

 Manufacture. By C. C. Hawkins and 

 F. Wallis. New York : Macmillan & 

 Co. Pp. 520. 



Nothing 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 alter- 

 nators. " 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 method- 

 ical analysis of dynamos of the causes and 

 reasons why they have assumed their pres- 

 ent shape if only it be complete and accu- 

 rate, 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 descrip- 

 tion of actual machines as manufactured, 

 and the practical design of one or more dy- 

 namos for given outputs. This scheme we 

 have endeavored to carry out." The au- 

 thors have taken pains to uuite practice and 

 theory in this treatise and to avoid mathe- 

 matics and technicalities that were avoid- 

 able. There are one hundred and ninety 

 illustrations, including cuts of a number of 

 typical dynamos. 



Descriptive Inorganic General Chemistry. 

 By Paul C. Freer, Ph. D. (Munich). 

 Boston : Allyn & Bacon. Pp. 550. 



This 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 chap- 

 ter 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, hydro- 

 gen, 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 phenom- 

 ena which are mentioned in this work which 

 does not find its analogon in some other por- 

 tion of the field of chemical study. The 

 attempt has been made especially to call at- 

 tention to the influence exerted by the nature 

 of the elements which make up a chemical 

 compound upon the character of that com- 

 pound 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 formula? are con- 

 servative. 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. Rem- 

 sen. There is an appendix of some forty 

 pages of laboratory notes, which is "not in- 

 tended as a laboratory manual, but mainly 

 as a guide to both teacher and pupil in com- 

 piling a list of experiments." 



Churches and Castles of Medieval France. 

 By Walter Cranston Larned. New 

 York : Charles Scribner's Sons. Pp. 236, 

 with Plates. Price, $1.50. 



This book, the author says, is a record 

 of a traveler's impressions of the great monu- 

 ments of France, published in the hope that 

 it may bring others to visit them. " It is 

 easy for the student to get accurate informa- 

 tion 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 pre- 



