ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 1 1 5 



illustrate our present knowledge of the subject. A glossary of technical 

 terms is appended. 



Fracture of Metals under repeated Alternations of Stress.* — J. A. 

 Ewing and J. C. W. Humphrey have investigated by means of the 

 Microscope the process by which iron becomes " fatigued " and breaks 

 down, when subjected to repeated reversals of stress. It is shown that, 

 although the greatest stress may be much within the limits of elasticity, it 

 produces rupture after many reversals. The first visible effect is the 

 production of slip-bands here and there on individual crystals. These 

 gradually become more numerous. They also become accentuated and 

 broadened, and their edges turn rough and burred, apparently as a 

 result of grinding of one surface on the other over the plane in which 

 the slip has occurred. At a later stage certain of the slip-bands develop 

 into cracks, the cracks spread from crystal to crystal, and fracture 

 ensues. 



Volatilisation and Recrystallisation of the Platinum Metals.t 

 For the measurement of high temperatures by means of thermo-elements, 

 it is usual to employ a combination of a platinum wire with one of 

 platin-rh odium (Le Chatelier), or with one of platin-iridium (Barns). 

 L. Holborn and F. Henning have undertaken experiments to test the 

 suitability of these materials, and especially to discover whether the 

 crystalline structure suffered any degeneration in consequence of pro- 

 longed heating. It was found that alloys of platinum and iridium at a 

 temperature of 1500° C. lose weight considerably, and metallographic 

 examination showed extensive disintegration of structure. The other 

 metals and alloys were practically unchanged. 



Campbell, W. — Upon the Structure of Metals and Binary Alloys. 



[Discusses methods, crystal ine structure, effects of strain, effects of heat 

 treatment, and represintativi s of the various groups of binary alloys.] 

 MetaUogmphist, V. (1902) pp. 2S6-334 (3S figs.). 



Houghton, S. A. — The Internal Structure of Iron and Steel with special re- 

 ference to defective Material. 



[A very clearly written paper, copiously illustrated with excellent photo- 

 micros.] Mdallographist, V. (1902) pp. 257-So (34 figs.). 



* Proc. Boy. Soc, lxxi. (1902) p. 79. 



f S.B. d. k. Preuss. Akad.d."\Yis8. zu Berlin, xxxix. (1902) pp. f 3>J-13 (11 photo- 

 micros). 



I 2 



