ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 437 



hydrogen. A number of photomicrographs accompany the paper, and 

 bring out very clearly these points in examining microscopically surfaces 

 etched with various cupric re-agents. F. I. G. R. 



Constitution of Chromium-tungsten Steels. — {Chemical and 

 MetaJlurgiml Engineermg, May 4, 1U21, 24, No. 18). Recent Japanese 

 work throwing light upon the complex reactions giving self-hardening 

 and red-hardness properties to modern high speed steels. Edwards' 

 views on like subjects are also briefly given. 



Structure of Tungsten Steels. — {Chemical and Metallurgical 

 Engineering, April '21, 1921, 24, No. 17). Review of Honda and 

 ]\Iurakami's work, presenting their principal conclusions as to the 

 structure and constitution of tungsten-iron-carbon alloys. Reactions 

 between irou-tungstide and iron and tungsten carbides are responsible 

 for great complexity. 



Crystalline Structure of Metals.— Zay Jeffeies and R. S. 

 Aecher {Chemical and Metallurgical Engineering, May 4, 1921, 24, 

 No. 18). A brief definition of crystallinity ; a discussion of the 

 methods used in X-ray analysis of atomic spacing ; and a statement of 

 the results of such studies made up to the present time. 



