REVIEWS 783 



in these editions ; this note refers to the possibility that the same enzyme may be 

 active in different and allied reactions which it accelerates unequally. The 

 possibilities of the biological applications of this hypothesis are fascinating, and 

 the simplicity of the statement, one reaction, one enzyme, is more apparent than 

 real when dealing with actual physiological problems. 



J. H. P. 



Metallography. By Cecil H. Desch, D.Sc, Ph.D. Second Edition, with 

 14 plates and 108 diagrams. [Pp. x + 431.] (London : Longmans, Green 

 & Co., 1913. Price 9^.) 



THE first edition of Dr. Desch's book is so well known to metallographists that no 

 very detailed review of the second edition is called for. The new features do not 

 affect the general plan, although by bringing the book up to date and by correcting 

 earlier errors they naturally enhance the already high value of the work. The 

 treatment of the whole subject might well serve as a model to all scientific authors, 

 and the reader is continually made to feel the sense of satisfaction always imparted 

 by clear and logical exposition united with cogent criticism — factors which diversity 

 of knowledge, as well as depth, on the part of the author, alone can produce. 

 The correlation between metallographic studies and research in other physico- 

 chemical fields is an intimate one, and in the writer's mind the greatest value of 

 this book is that it forces one to realise this intimacy, and indicates very clearly 

 the mutual benefits which metallography and the rest of physical chemistry may 

 expect of one another. In this way, and by his systematic method of examining 

 each part of his subject, Dr. Desch has produced a book which will certainly 

 continue for a long time to be one of the most stimulating works of its kind, alike 

 to workers in physical chemistry and to specialists in metallography. 



I. M. 



Modem Seismology. By G. W. Walker, A.R.C.Sc, M.A., F.R.S. [Pp. 

 xii-f 88. With 13 plates and diagrams.] (London : Longmans, Green 

 & Co., 1913. Price 5^.) 



This work is one of the monographs on physics edited by Sir J. J. Thomson and 

 Dr. H. Horton, of the Cavendish Laboratory. The geological aspects of earth- 

 quakes are purposely avoided, and seismographs and their records are treated 

 from a mathematical point of view. The author has been profoundly influenced 

 by the vigorous personality of John Milne, with whom he associates Wiechert and 

 Galitzin as the most prominent workers in seismology. Photographs and descrip- 

 tions are given of the best modern types of seismograph, and the introduction ot 

 artificial "damping" is discussed. Even to the non-mathematical, the successive 

 triumphs over unexpected difficulties must appeal. On page 25 we learn, after a 

 discussion of mechanical registration, that " the writing point may remain at rest 

 anywhere within a range of 2r, and discontinuities of the magnitude may occur in 

 the trace." The author's experiments show, moreover, that r is not a constant, but 

 depends on the state of the smoked surface on which registration takes place and 

 on the amplitude of the movement. We are immediately reassured by the 

 statement that with care the value of r may be reduced on Wiechert instruments 

 to " a few tenth millimetres." 



The student will not find much in the book about the nature of earthquake- 

 waves ; he is supposed to have assimilated this in previous reading. The author's 

 familiarity with the appearance and interpretation of seismographic records leads 

 him to be very concise, even when he discusses their interpretation. A few 



