REVIEWS 157 



of the atom with its " steady " electronic orbits. One cannot praise too 

 highly the exceedingly careful manner in which the author has separated and 

 discussed the two features which are common to the laws of all series spectra, 

 bringing home with great point and clarity Ritz's principle of combination 

 before going on to the well-known Balmer-Rydberg-Runge numerical relation- 

 ships. In no explanation has the writer seen the relation of lines in a spectrum 

 to " terms " so lucidly put. There follow excellent accounts of the quantum 

 hypothesis and its peculiar relation to our classical dynamics, of Bohr's 

 Theory and the generalisation of it due to Sommerfield, of the quantum treat- 

 ment of the Zeeman and Stark effects, and of the bearing of relativity theory 

 on the explanation of the fine structure of high-frequency lines. Sections 

 on the intensity of spectral lines and on band spectra conclude a volume 

 which no student of physics should fail to read if he wishes to see a very large 

 body of recent theoretical and practical research dealt with in a compass 

 remarkably small considering the wealth of material available for selection. 



J.R. 



L'atome— Sa structure, sa forme. Les Edifices physicochimiques. Tome I. 



Par Dr. Achalme. [Pp. 244.] (Paris: Payot et Cie, 1921. Price 

 15 frs.) 



This work is the first of a series of eight volumes, in which it is sought to give 

 a rational interpretation of all chemical and biological phenomena. In the 

 present volume the author has exercised much ingenuity and but little 

 circumspection in the elaboration of a theory of the structure of the atom. 

 On the assumption that the charge on the electron is twice as great as that on 

 the positive hydrogen nucleus, he constructs diagrams illustrating the atomic 

 structure of the principal elements. 



The book appears to have been written some years ago, for no mention is 

 made of the recent theoretical and experimental work on the subject. Thus 

 it is stated on page 76 that chlorine consists of isotopes of atomic weights 

 35 and 39, whereas Aston has shown these to be 35 and 37 respectively. 



The work is almost entirely speculative. 



W. E. G. 



CHEMISTRY 



A Comprehensive Treatise on Inorganic and Theoretical Chemistry. By 



J. W. Mellor, D.Sc. [Vol. I (H ; O), pp. xvi + 1065, with 274 

 diagrams ; Vol. II (F, CI, Br, I. Li, Na, K, Rb, Cs), pp. viii + 894, 

 with 93 diagrams.] (London : Longmans, Green & Co., 1922. Price 

 ;^3 35. net each volume.) 



In the early days of chemistry it was the custom for textbooks and treatises 

 to be written by one or two chemists who were able to assimilate the whole, 

 or one of the chief divisions, of chemistry, and then to present it in readable 

 form for the benefit of others ; we have only to tliink of Thompson's New 

 System, of Roscoe and Schorlemmer's Inorganic Chemistry, or of Meyer and 

 Jacobson's Lehrbuch der organischen Chemie, to realise this. 



At the present day, however, the tendencies have been in two directions : 

 either for individuals to write monographs dealing with certain special 

 subjects with which they are familiar, or else for a number of writers to 

 collaborate under a general editor. The first method has the advantage 

 that the expert can write up his pet subject in a manner not otherwise 

 possible, but there is the disadvantage that the multiplicity of actual or 

 threatened monographs is so great that no chemist has time to do much more 

 than to glance through a few of them. 



The second method has the advantage of keeping subjects within strict 

 limits, but there is the inevitable disadvantage that a book written by several 



