ABSTRACTS OF RECENT TECHNICAL BOOKS 653 



discoveries and improvements in the arts of experimentation, it 

 became possible to measure the charge and the mass of the atom of 

 negative electricity; to measure the charges, masses and magnetic 

 moments of the atoms of the chemical elements; to study the processes 

 of detaching atoms of electricity from atoms of matter; and to extend 

 the spectra of the elements by detecting a host of radiations previously 

 unknown and determining their frequencies. The data so assembled, 

 together with observations upon the encounters of electrified particles 

 with atoms, illuminated the relations between the elements, and 

 contributed to the design of an atom-model which has already in- 

 spired many discoveries. Among these the greatest was the discover}- 

 of the Stationary States, which replaced the early way of interpreting 

 spectra by a new and strikingly fruitful procedure, and taught ex- 

 perimenters to seek after and find a multitude of new phenomena 

 of the most varied interest and importance in almost every field of 

 physics. To name only two of the fields thus enriched: the flow of 

 electricity through gases, and the conditions for the excitation of 

 radiation, have been clarified in most unexpected fashion since the 

 recognition of the Stationary States. 



The book "Contemporary Physics," by Dr. Darrow, is devoted to 

 these fundamental discoveries and to some of their consequences. It 

 might be described as an introduction to the Theory of Atomic Struc- 

 ture, in the present day acceptance of this phrase; for the phenomena 

 with which it deals have nearly all been used in designing atom models, 

 and reciprocally a great many of them have been discovered in the 

 course of making experimental tests of predictions based upon atom- 

 models. These models are in fact among the most important features 

 of contemporary physics and it would neither be possible nor desir- 

 able to omit them from such a book; for they are undoubtedly valu- 

 able, and the phenomena could hardly be described briefly and clearly 

 without making use of them. Nevertheless, the actual facts of ex- 

 perience receive the greater emphasis, for they are the permanent 

 and unassailable parts of the recent extensions of physics. 



The book is developed from articles which have been appearing 

 in the Bell System Technical Journal under the general title 

 Some Contemporary Advances in Physics, apart from the articles con- 

 cerning Hertzian waves and conduction of electricity in solids, which 

 fall outside of the field to which it is restricted. The remaining 

 articles, which were originally self-contained and separate, were 

 largely rewritten in order to Iniild out of them a coherent presenta- 

 tion of a unified field, and in the course of the rewriting they were 

 nearly doubled in length by addition of new material. The book may 



