484 SCIENCE PROGRESS • 



terms and concepts introduced, even after consulting the glossary at the end 

 of the book. (It may be mentioned, in passing, that an electrometer is defined 

 as " an instrument for measuring an electric charge.") 



Yet for one who has some knowledge of the subject but no opportunity 

 of consulting original papers the book serves a useful purpose, as it gives a 

 comprehensive account, without mathematical analysis, of current views of 

 the structure of the atom and of the nature of energy. At times the exposi- 

 tion fails to carry conviction and interest through the omission of details. 

 But in so small a space it was impossible to include everything, and the book 

 gives up-to-date information over a wide field. 



G. A. S. 



Some Physico-chemical Themes. By A. W. Stewart, D.Sc. [Pp. xii + 419, 

 with 5 plates and 37 diagrams in the text.] (London : Longmans, 

 Green & Co. Price 21s. net.) 



This volume consists of a series of essays on Physical Chemistry, written in 

 an especially interesting and vivid manner. The author does not cover the 

 whole field of physical chemistry in these essays, but makes a selection from 

 some of the more interesting branches of the subject, which have been arranged 

 so as to give a connecting thread of interest throughout the book. In the 

 development of his themes the author has no hesitation in making new 

 tracks for himself in the unloiown land between related sciences. 



Some of the chapters, that on pseudo-acids and portions of the other 

 essays, have appeared before in the author's textbook. Recent Advances in 

 Physical and Inorganic Chemistry. The essay on the development of the 

 periodic law is especially good ; in this, and in subsequent chapters, he 

 collects together, in a very readable form, information relating to the periodic 

 table which has hitherto been scattered through the literature, and in many 

 cases has been inaccessible to the ordinary student of chemistry. In the 

 preface emphasis is laid on the necessity for a wider study of the physical 

 chemistry of organic compounds, and, in some of his themes, he devotes 

 especial attention to this branch of chemistry. 



The author, however, has his " crochets " ; he dislikes " Ostwaldian " 

 physical chemistry, with the result that the chapter on the theory of indicators 

 is entirely lacking in the physico-chemical aspect ; he is unfair to Werner's 

 theory in the chapter on chemical afi&nity ; he hastily condemns the Bohr 

 theory, which he considers as utterly worthless from the point of view of 

 chemistry and radio-chemistry. It is to be regretted that the author does not 

 hold a more even balance between the conflicting theories of modern chemistry. 

 Objection may be made to the statement on p. 121 that colour production in 

 salts is " absolutely independent of ionisation " ; according to modern views 

 on the structure of crystals ionisation is a characteristic feature of salts in the 

 solid state. 



With the aid of this book, the student should be able to grasp the trend of 

 physico-chemical research at the present day, and, since the book provides its 

 own antidote, will find Dr. Stewart's independence of view very refreshing and 

 stimulating. 



A useful bibliography is appended. 



W. E. G. 



The Emission of Electrons from Hot Bodies. By O. W. Richardson, F.R.S. 

 Second Edition. [Pp. vii + 315.] (London : Longmans, Green & 

 Co. Price 165. net.) 



This is the second edition of a very well-known monograph, the first edition 

 of which appeared in 1916. The author has, of course, a world-wide reputation 

 as a pioneer and an indefatigable investigator in the subject of thermionics. 

 The work still holds the field as the most complete exposition of the subject 



