178 SCIENCE PROGRESS 



less than of the detailed practice, of analyses, are very carefully and clearly given, 

 and the student is not ordered to take a given precaution without being shown 

 exactly why he should do so. In fact, the whole scheme is rational and satisfactory, 

 and there are a great many features, such as the indication of the time for each 

 analysis, which lend special worth to the book. 



I. M. 



Photochemistry. By S. E. Sheppard, D.Sc. [Pp. ix + 461. Illustrations and 

 figures.] Text-Books of Physical Chemistry. (London: Longmans, Green 

 & Co., 19 1 4. Price 12s. 6d.) 



IT is no easy matter to review a book like this ; for the reviewer cannot claim to 

 be an authority on photochemistry, hence he feels some diffidence in expressing 

 views which are in the nature of unfavourable criticism. No such criticism would 

 be offered if the series of which this book is one were designed for the reading of 

 specialists only ; but the volumes already issued appeal to a wider public, and 

 therefore it is legitimate to regard the work from a not too exalted standpoint. 



Firstly, the treatment throughout is of a very physical kind, and although 

 obviously a great deal of photochemistry is pure physics, a more chemical outlook 

 upon it than we find here would have been welcome. The chemical reader wishes 

 to have, in the first place, information as to the facts of the reactions set up or 

 modified by light, and he expects that information to be conveyed in ordinary 

 chemical phraseology. He is then prepared for whatever theories and hypotheses 

 may be forthcoming as to the reasons for such actions, together with the further 

 facts, chemical and physical, which lend support to these. This is doubtless a 

 limited aspect of the matter ; but the point is that this limited aspect is photo- 

 chemistry, in which science physics must play an auxiliary and not a preponderating 

 role. In this book there is a large amount of extremely interesting matter, but its 

 relevance to chemistry is not always plain. And although by diligent study the 

 reader will come to an understanding of what is set forth, he will find that con- 

 siderable rearrangement, including discrimination of well-grounded theories from 

 speculation and analogy, occupies much of his time after reading. 



It would be presumption to deny that an author whose knowledge is as profound 

 and whose enthusiasm is so great as Dr. Sheppard's has the right to choose his 

 own way of attacking his own subject, even though the result may turn out to be 

 caviare to the general. But (and this is the last criticism) it seems to the writer a 

 vast pity that so much interesting and stimulating material should be set forth in a 

 style which jars constantly upon the literary sense of an ordinary individual, and 

 which by its obscurity (in reality due to a meticulous regard for the mot juste) is a 

 real check to the appreciation which the author surely should receive. 



It must be insisted on once more that these remarks represent the views of a 

 chemist only ; those who specialise in the chemical effects of light cannot fail to 

 gain by the collection together into one volume of so much that is significant in the 

 subject. 



I. M. 



An Introduction to the Chemistry of Plant Products. By P. Haas and 

 T. G. Hill. [Pp.401. With 5 text figures.] (London : Longmans, Green 

 & Co., 1913. Price 7s. 6d. net.) 



It should be said at the outset that this book will be of very great value to 

 the botanist ; published at such a commendably reasonable price, it should find 

 a considerable public. There is no other English book in which the reader 



