i 7 2 SCIENCE PROGRESS 



technology, and in this respect is a manifestation of the present tendency to bring 

 the theorems of physical chemistry to bear on the problems of technical chemistry. 

 An example of successful work on these lines has been already furnished by the 

 application of the phase rule to such problems as the nature of iron-carbon alloys. 

 In this and other cases it has once again been found that what appears to be 

 nothing more than "pure" science may turn out to be most necessary to the 

 sound advance of " applied " science. The two things are complementary to each 

 other, not mutually exclusive. 



The volume under review had its origin in a course of lectures delivered some 

 three years ago by Prof. Haber to an audience fairly familiar with the chemical 

 and technical side of the subject. A good deal of space is therefore devoted to 

 the development of the mechanical theory of heat, and the author's treatment of 

 this subject will be found fresh and illuminating by those readers who are chemists 

 rather than mathematicians. The author has chosen Helmholtz's point of view, 

 and regards a chemical reaction as having a latent heat just like any simple change 

 in the state of aggregation. It is claimed that the theoretical and practical con- 

 nection between gas reactions and the dissociation and vaporisation of solids can 

 be much more readily appreciated from this standpoint. 



Owing doubtless to the author's anxiety to provide a sure foundation, the first 

 hundred pages or so of the book contain very little that has anything directly to 

 do with technical gas reactions, so that the chemical reader especially must be 

 prepared to exercise patience. Among the gas reactions which are discussed from 

 the thermodynamical point of view are the union of nitrogen and oxygen in the 

 electric arc, the Deacon chlorine process, the water-gas reaction, and the contact 

 process for the manufacture of sulphuric acid. Special emphasis is laid on the 

 importance of specific heats in gaseous reactions, and an interesting chapter is 

 included dealing in detail with the methods used and the results obtained in this 

 field. In view of the amount of work which is being done at present on the 

 problems discussed in this volume, it is satisfactory to find that appendices to 

 several chapters have been specially written by the author for the English trans- 

 lation, so that the latter has been brought up to date. 



The translator has done his work satisfactorily, and there is little trace of the 

 outline of the original German sentences, such as one can frequently detect in 

 translations of this kind. Occasionally a little more independence of the original 

 might have been shown, as for example, in the choice of a symbol for " room 

 temperature"; the letters Z. T. betray their origin. This, however, is a trivial 

 matter, scarcely worth the comment, when the translator's work is so generally 

 excellent. 



J. C. Philip. 



Modern Electrical Theory. By Norman R. Campbell. [Pp. xii. + 332.] 

 (Cambridge : University Press ; price ys. bd. net). 



NOT the least characteristic feature of this book is the tendency of the author 

 throughout to act as his own critic. This peculiarity appears even in the prefatory 

 description of the scope of the work. While stating that his original intention was 

 to provide a book which would appeal to students already well grounded in physics 

 but unacquainted with modern developments, the author admits that a consider- 

 able part of the work will be already familiar to such students. Similarly in the 

 book itself, from time to time, some particular point of view is presented, and 

 then, as likely as not, a statement follows of effect equivalent to this : " It seems 



