Chemistry and Physics. 79 



15. Electricity, Sound and Light • by R. A. Millikan and J. 

 Mills. Pp. 389. Boston and New York, 1908 (Ginn & Co.). — 

 "This book represents primarily an attempt to secure a satisfac- 

 tory articulation of the laboratory and class-room phases of 

 instruction in physics." "It is designed to occupy a half-year 

 of daily work, two hours per day, in either the freshman, sopho- 

 more, or junior years of the college or technical-school course." 

 This text-book supplements the course contemplated in Millikan's 

 "Mechanics, Molecular-Physics and Heat." 



The authors have designed (and tested) the entire course in 

 such a wholesome, common-sense way that we are of the opinion 

 that an instructor who adopts their text-books and follows their 

 plans will approximate more closely to ideal conditions of teach- 

 ing-efficiency than can be attained by the customary scheme of 

 independent class-room and laboratory courses. h. s. u. 



16. Einfuhrnng in die Elektrotechnih ; by C. Helnke. Pp. 

 xix, 501; with 512 figures. Leipzig, 1909 (S. Hirzel).— This 

 text embodies, in an attractive and useful form, the author's 

 course of lectures in the Munich Technical School ; it is 

 designed as a connecting link between abstract electrophysics 

 and the technical applications of electricity. The subject matter 

 is treated under the following seven captions: Introduction; 

 mechanical analogies helpful in comprehending the fundamental 

 phenomena of electromagnetism ; the generation of potential dif- 

 ference ; the technical generation of electrical energy ; the 

 utilization of electrical power by its transformation into other 

 forms of energy; electrical measuring instruments; leads and 

 accessory apparatus. The discussions are direct and clear ; the 

 illustrations and mechanical features, without exception, excellent. 

 Topics of the articles are printed on the margin of the page, but 

 there is no index. d. a. k. 



IT. La Machine a Influence, son J&voltition, sa Theorie ; by 

 V. Schaffers. Pp. vii, 506 ; with 197 figures. Paris, 1908 

 (Gauthier-Villars). — The purpose of this book, as stated by the 

 author, is to assemble, coordinate and perfect, so far as possible, all 

 of value that has been published on influence machines. A more 

 comprehensive and detailed description is given, of all of the 

 important influence machines, as well as of electrostatic motors, 

 than is to be found in' any previous compilation ; and a serious 

 attempt is made to cover the theory of each part. The author 

 has made a number of original contributions to the subject. His 

 hydraulic models are of some interest ; but of doubtful value in 

 elucidating the principles of the machines. The results of a large 

 number of quantitative measurements are given, showing the 

 quantity of electricity produced per second, the potential differ- 

 ence maintained and the efficiency of the several types of 

 machines under varying conditions of atmosphere and manipula- 

 tion. In all probability the influence machine has attained, in 

 design if not in theory, its final stage of development ; in view 



