486 SCIENCE PROGRESS 



theories. References to all important original papers are given, and a 

 bibliography of literature connected with the subject is put at the end of the 

 book, but there seems to be a scarcity of reference to English works. 



J. R. 



Rayonnement et Gravitation. Par FiSlix Mich aud. [Pp. viii + 6i.] (Paris: 

 Gauthier-Villars. Price 6 frs.) 



This is an intensely interesting book. The author points out that it is 

 dif&cult nowadays to decide what is simple. Many customary concepts 

 have only the appearance of simplicity. It is best therefore, in attempting 

 to explain physical facts, to adopt a suitable starting-point, and Radiation 

 is chosen as such. 



The first part of the book deals with the optics of bodies in movement. 

 The experimental facts to be explained are clearly stated. Their explanation 

 is next considered in an order which differs considerably from the usual one. 

 The only postulates used in the first part of the book are the energetics of 

 Radiation and the Principle of Relativity restricted to uniform translation. 



Chapter V, dealing with transmission of light in different media, is character- 

 istic of the author's lucidity. The assumptions are clearly stated and the 

 deductions are in places elegant. 



On the bans of Radiation the second part of the book builds up Gravitation, 

 Inertia, Cohesion, Capillarity, Electricity and Magnetism, the last-mentioned, 

 however, only in an outline fashion. 



In Chapter VI we get a neat explanation of photo phoresis. In the 

 same chapter gravitation phenomena are stated to have their origin in the 

 capability of matter to absorb a radiation filling all space. The energy of 

 radio-active changes receives here an interpretation in terms of radiation. 



In later chapters physical interpretations are given to the inertia and 

 weight of radiation, the anomaly of the perihelion of Mercury, and the 

 dependence of mass on velocity. 



J. R. 



General Physics, and its application to industry and everyday life. By 

 Edwin S. Ferry, Professor of Physics in Purdue University. [Pp. 

 xvi + 732, with 600 figures.] (New York: Wiley & Sons ; London : 

 Chapman & Hall, 1921. Price 24s. net.) 



Our admiration for American textbooks in the past has been restricted to 

 those deaUng in an elementary way with everyday physics or, rather, everyday 

 science. Books above this standard have generally contained peculiarities 

 (to put it politely) in their treatment of fundamental principles which has 

 made it impossible to recommend their use in this country. Professor 

 Ferry's textbook is not subject to this disadvantage, and he has to be con- 

 gratulated on having written a novel — a refreshingly novel — textbook of 

 physics of a standard rather higher than that demanded by the intermediate 

 examination of the English Universities. With the orthodox division of 

 the subject : Dynamics and General Properties of Matter, Sound, Heat, 

 Electricity, Light, the author has combined a quite unorthodox disregard 

 of the limits usually imposed by the examination syllabus with a novelty 

 and thoroughness of exposition, illustration, and example which is as unusual 

 as it is welcome. There are about 1,000 problems for the student to solve 

 — many of them quite new to the reviewer — including about 700 numerical 

 examples at the end of the book to which answers are given. 



We should like to recommend the book for ordinary class use : we can do 

 so for those cases in which an external examination is not in immediate view. 

 We are quite sure that no teacher who adds it to his collection will regret 

 his purchase : or forget that it is there ! 



D. O. W. 



