REVIEWS 171 



inaccurate data, and it is well that the investigator should take every precaution to 

 avoid adding to their number." 



It is satisfactory to note that due importance is given to physical properties as 

 means of investigation. Unfortunately the metallurgist does not always value the 

 conclusions which can be drawn from a study of such properties ; while, on the 

 other hand, few physicists fully understand or sympathise with the purpose of 

 metallography. In this connection Dr. Desch's remarks are worthy of quotation. 

 He says : " In addition to its value in providing auxiliary methods of research, the 

 study of the physical properties of alloys is of importance in quite another 

 direction. The practical utility of alloys is dependent on their possession of 

 certain physical characteristics. ... It is important, therefore, to establish such 

 a relation between the constitution of a series of alloys — most conveniently 

 expressed in the form of the thermal equilibrium diagram — and their physical 

 properties, that the latter may be predicted for any given alloy by. an inspection 

 of the diagram." 



At the present time the metallurgist and engineer are devoting much attention 

 to the problem of the corrosion of metals, and the chapter in which this matter is 

 considered expresses very clearly the chief theories which are now accepted on 

 the subject. 



It is to be regretted that the chapter on the metallography of iron and steel did 

 not receive more adequate treatment. The subject, of course, is extensive, and 

 in a book of a general character, such as this, an exhaustive account is not needed ; 

 moreover, as the views held on the thermal equilibrium of iron and carbon are 

 still conflicting, the time has hardly arrived for a severe criticism on any attempt 

 to give a brief and concise explanation. There is no doubt that when our know- 

 ledge is more exact, the metallography of iron and steel will require a separate 

 volume. The chief defect in this chapter is in the photographs ; there are too 

 few and of too low a magnification : for instance, martensite is not represented 

 at all, while the plate showing pearlite is not good. It would have been made 

 more valuable if illustrated with photomicrographs of the chief constituents ; 

 photographs of grey cast-iron, annealed and quenched steels, and high and low 

 carbon steels might, with advantage, have been inserted. 



The chapter on industrial alloys may disappoint some, but, strictly speaking, 

 it is beyond the province of this book ; however, what has been given is very 

 useful and quite in order, for it indicates the nature of such alloys and on what 

 their value depends. 



Ample references are given throughout the book showing that the author has 

 spared neither time nor trouble in making his work thoroughly useful. 



There is an unimportant misprint on page 12, line 4, which also occurs in the 

 first line of the preface. 



Dr. Desch is to be congratulated on writing a concise, yet, on the whole, 

 comprehensive book on the science of metallography. 



E. O. COURTMAN. 



Report on the Mines and Mineral Resources of Natal. By F. H. Hatch, 

 Ph.D., M.Inst.M.E. [Pp. xii -f 155.] (London: Published by Order of 

 the Natal Government and printed by Richard Clay & Sons, Ltd., 1910.) 



This publication is the first result of the author's recent visit to Natal, during 

 which he was able to make an extensive collection of the rocks and minerals 



