ZOOLOGY AND BOTANY, MICROSCOPY, ETC 385 



Manufacture of Cartridge Cases for Quick-firing Guns.* — L. 

 Cubillo and A. P. Head describe the properties of the brass (Cu 67 p.c. 

 Zn 33 p.c.) used for this purpose. An examination of the cooling curve 

 of this alloy leads to the conclusion that it is a eutectic. The cold- 

 drawing operations to which the metal is subjected necessitate frequent 

 annealing ; the most suitable temperature is 620°-650° C. The value of 

 microscopic examination of metals is pointed out, and five photo- 

 micrographs of brass, both in the annealed and cold worked states, are 

 given. The processes of manufacture of cases are described in detail. 



Iron-Carbon Alloys with high percentages of Carbon.j — Recog- 

 nising the unsatisfactory character of the theory of iron-carbon alloys, 

 elaborated by Roozeboom, as applied to high carbon alloys, F. Wust 

 determined the cooling curves of a series containing 2* 56-4 "82 p.c. 

 carbon. The percentage of elements present other than iron and carbon 

 was very small. The curves relating to eight of the alloys are given. 

 According to the theory, graphite should be the first constituent to 

 separate during solidification of the 4 ■ 82 p.c. alloy, and should rise to 

 the surface owing to its relatively low specific gravity. This was not 

 found to be the case. The lower freezing point varied from 1112°- 

 1149° C. No thermal change was detected between this point and the 

 evolution of heat caused by the formation of pearlite at about 700° C. 

 The author's work supports the conjectures of Osmond and Heyn, that 

 the formation of cementite takes place at 1185° C. The structure of 

 many of the alloys, illustrated by photomicrographs, is described in 

 detail. The non-reversible change (cementite = ferrite + temper carbon) 

 occurring when alloys containing free cementite are heated at a high 

 temperature, is held to uphold Heyn's assumption that the system 

 ferrite + carbon is stable, the other systems being phenomena due to 

 rapid cooling. 



A Defective Bar of Tool Steel. J — C. E. Corson gives a number of 

 interesting photomicrographs of a bar of crucible steel containing 

 1*72 p.c. carbon. A finishing tool made from the steel failed after 

 being in use a very short time. The fracture at one place in the bar 

 was fine grained, while at another point it was coarse. The author con- 

 cludes that the steel had been slowly cooled from a temperature varying 

 considerably in different parts of the bar. 



Liquid Crystals and Plastic Crystals.§ — Certain organic bodies on 

 melting yield a liquid which is not clear, and has the property of double 

 refraction, indicating a decided orientation, though no indication of 

 crystalline structure is afforded by external form. At a somewhat 

 higher temperature the liquid becomes clear, and loses its abnormal 

 optical properties. Other substances, of great viscosity, exist as soft 

 crystals, frequently having rounded extremities. These plastic crystals 

 are deformed by the application of very slight forces. An account of 

 these singular phenomena is given by Etienne, who points out that 



* Engineering, lxxx. (1905) pp. 548-75 (47 figs.). 



f Iron and Steel Mag., xi. (1906) pp. 185-211 (27 figs.). 



% Tom. cit., pp. 281-6 (10 figs.). 



§ Rev. Metallurgie, iii. (1906) pp. 129-36 (6 figs.). 



June 20th, 1906 2 



