486 



SCIENCE 



[N. S. Vol. XL. No. 1031 



point of view sucli as is so characteristic of 

 most popular science writing, but instead a 

 clear presentation of current scientific opinion 

 as it has been incorporated into Professor 

 Ames's own thinking. 



The first lecture lays the foundation for the 

 remainder by an admirable and a very discern- 

 ing historical discussion of the introduction 

 into physics of the concepts of mass, force, 

 the ether, energy, molecules, atoms and cor- 

 puscles. Concerning this chapter I would 

 make but two comments: It is a pity that all 

 other writers have not shown as much discri- 

 mination in the use of the terms corpuscle and 

 electron. The latter term was introduced 

 into physics in 1891 by G. Johnstone Storey 

 to denote the " natural unit of electricity " 

 altogether without reference to the inertia 

 which might he associated with it and it is 

 surely desirable to-day to have some word to 

 denote this idea. Electron is obviously the 

 logical word for the purpose. A negative 

 electron when associated with the smallest 

 inertia which is ever found to accompany an 

 electron, namely, l/1830th that of the hydrogen 

 atom, was called by Thomson a corpuscle, and 

 Professor Ames wisely follows this usage. I can 

 not myself be quite so enthusiastic about the 

 statement that " a system has potential energy 

 if it is in its natural condition " or indeed 

 about the way in which the idea of potential 

 energy is used throughout the first and second 

 chapters, especially throughout the second, 

 which deals primarily with the subject of elec- 

 tromagnetic mass. There is a sentence in one 

 of the later lectures which reads as follows : 

 " There is no word, I think, in our language 

 which is so much used to conceal ignorance as 

 ' heat,' and no word about which there is so 

 much confusion of ideas as ' temperature.' " 

 I should like to insert in each clause " except 

 the word energy." The third lecture treats 

 together the newest and the oldest of the 

 departments of physics, namely, radioactivity 

 and gravitation, the former quite briefly (ex- 

 cellent judgment again), the latter quite at 

 length but with a freshness and power which 

 is born only of a very thorough and profound 

 knowledge of original sources. 



The fourth, fifth and sixth lectures are the 

 finest and most stimulating of the course. 

 They deal respectively with (4) the problems 

 of radiation, (5) the electron theory of con- 

 duction, thermoionics and magnetism, (6) 

 models of atoms and fundamental concepts 

 of nature. These chapters represent I think 

 the best general discussion which has appeared 

 in English of the big problems which the re- 

 searches of the past two decades have pre- 

 sented to modem physics. 



E. A. MlLLIKAN 



Ryekson Laboratory, 

 University op Chicago 



The Chemistry of Cattle Feeding and Dairy- 

 ing. By J. Allan Mureay. London, Long- 

 mans, Green and Co. 1914. Octavo. Pp. 

 343. 



This book discusses briefly (1) the constitu- 

 ents of plants and animals, (2) the nutritive 

 requirements of animals, (3) feeding stuffs 

 and (4) dairy chemistry. The treatment is, in 

 the main, elementary in character. The dis- 

 tinctive feature is an attempt to break away 

 from the Wolff and the Kellner feeding stand- 

 ards, especially in recognition of the fact that 

 the nutritive requirements of animals do not 

 vary directly as the live weight. The point of 

 view is rational, and the tentative formulae 

 suggested for the separate computation of food 

 requirements for maintenance, labor, milk 

 production, growth and fattening constitute a 

 notable step in a direction in which progress 

 is much to be desired. The discussion of the 

 chemistry of the subject is generally satisfac- 

 tory. 



The author's statements regarding the func- 

 tions of the mineral elements, and regarding 

 other matters of physiology and histology, are 

 frequently lacking in discrimination. We 

 quote a few such passages : 



Page 8: " The ingredients of the ash are not 

 ' mineral.' They are just as much organic mat- 

 ter as the fats or proteins." 



Page 9 : "It is probable, however, that the 

 chlorides naturally present in the food of 

 herbivora are suiEeient to provide all the hy- 

 drochloric acid required." 



