ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 391 



Hardness of Quenched Steels.*— A. Portevin and H. Berjot have 

 employed the Shore scleroscope and to a smaller extent the Brinell ball, 

 to determine the hardness of two steels containing " 32 and 1 ■ 4G p.c. 

 carbon, a steel containing 0'56 p.c. carbon, 1*46 p.c. silicon, and two 

 case-hardened steels originally containing, the one 0*13 p.c. carbon, 

 the other 0*09 p.c. carbon, 2*54 p.c. nickel. Specimens were tested 

 after hardening at different temperatures, and after hardening and 

 reheating to different temperatures for various lengths of time. The 

 indications of the scleroscope are rendered worthless by the presence of 

 hardening cracks or of a superficial decarbonised layer. If proper 

 precautions are taken, the scleroscope may safely be used for measuring 

 the hardness of quenched steels, and is especially suitable for testing 

 case-hardened steels, giving as it does the superficial hardness which 

 cannot be determined by the Brinell method. The measurement of 

 depth of cementation by the appearance of the fracture, is less reliable 

 than measurement by microscopic examination of a polished and etched 

 section. 



Cementation of Silicon Steels. f — L. Grenet has made comparative 

 cementation tests on a mild case-hardening steel and a steel contain- 

 ing 3 • 2 p.c. silicon, ■ 05 p.c. carbon. No cementation of the silicon steel 

 took place in wood charcoal, but in potassium ferrocyanide 1 p.c. carbon 

 was absorbed by the outer layer ■ 5 mm. thick, during a 6 hours' heat- 

 ing at 950° to 1000° C. No graphite was found in the cemented silicon 

 steel after slow cooling. 



Carbon-tungsten Steels. J — T. Swinden has studied the micro- 

 structure of three steels containing • 57, • 89 and 1 ■ 24 p.c. carbon, and 

 about 3 p.c. tungsten, quenched and air-cooled from different tempera- 

 tures. Some measurements of electrical resistance were made. Conclu- 

 sions drawn from earlier work § were confirmed. The lowering of the 

 Ar x point by high initial temperature does not appear to be due to the 

 formation of a carbide of tungsten, or a double carbide. Possibly a com- 

 pound Fe 3 W goes into solution at the " lowering temperature," and is 

 reprecipitated at the low point on cooling. 



Magnetic Properties of Alloys of Iron.|| — C. F. Burgess and J. Aston 

 have made magnetic and electrical tests of two series of alloys, iron- 

 nickel and iron-copper, prepared from electrolytic iron, and containing 

 very small percentages of impurities. The possible occurrence of the 

 compound Fe 2 Ni is indicated. 



Effect upon Steel of Sudden Changes of Temperature. % — B.Zschokke 

 ascribes the cracking of a tank, constructed of mild steel plate, to the 

 irequent rapid heating of the internal surface when the tank was used 

 for the preparation of a solution of caustic soda. Numerous experiments 



* Rev. Metallurgie, vii. (1910) pp. 61-75 (4 figs.). 

 t Comptes Rendus, cl. (1910) pp. 921-2. 



t Journ. Iron and Steel Inst., lxxx. (1909) pp. 223-56 (41 figs.). 

 § See this Journal, 1907, p. 640. 



|| Met. and Chem. Engineering (formerly Electroehem. and Met. Ind.), viii. 

 (1910) pp. 23-26, 79-81 (11 figs.). 



f Rev. Metallurgie, vii. (1910) pp. 165-82 (24 figs.). 



