ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 575 



layer of zinc. Cracks are always present in the coating. In electro- 

 galvanized iron, the coating may be pure zinc or zinc-iron alloys, Ijut a 

 very thin layer of " binding alloy " is always present. 



Meteoric Iron.* — It has been shown that Neumann's lines consist 

 of twinning lamellae. When occurring in kamacite, such lamellae, being 

 in a strained condition and accordingly more readily attacked by etching 

 reagents, are made visible when a polished surface is etched. F. Berwerth 

 and G. Tammann have heated at different temperatures and for different 

 lengths of time, specimens of meteoric kamacite in which Neumann's 

 lines were highly developed, to ascertain if the lines disappeared on 

 heating. At 727° C. four hours was insufficient to effect the transforma- 

 tion. At 878° C. the hues were much weakened in one minute, while 

 at 1050° C. the transformation was complete in one second. The 

 specimens were etched for three minutes with 3 p.c. nitric acid. 



The authors have also investigated the " burnt zone " in meteorites, 

 determining its thickness when occurring naturally, and studying its 

 artificial production. In the Avce meteorite, Neumann lines were 

 absent from the granular kamacite of the outer burnt zone. Below this 

 was a transition layer, in which lines began to appear, leading to the 

 normal internal structure showing well formed lines. Pieces of kamacite 

 wrapped in asbestos paper were strongly heated in the oxy-hydrogen 

 flame. The burnt zone thus produced showed three layers, oxide occur- 

 ring in the outermost, while Neumann lines were still found in the 

 inner layer. 



Mechanism of the Formation of Troostite.t — D. K. Bullens has 

 examined two steels containing 0*92 and 1*48 p.c. carbon and of great 

 purity. A bar of each, 6 in. in length, was heated at one end to 1050° C. 

 and quenched in water. The pieces were fractured lengthwise, polished, 

 etched with nitric acid in alcohol, or Kourliatoff's reagent, and micro- 

 scopically examined. A continuous photomicrograph, several feet in 

 length, was obtained from each piece, and depicted the transition from 

 austenite to the original steel. The various transition stages are described. 



Nomenclature of the Microscopic Constituents of Iron and Steel. | 

 H. M. Howe points out the utility of the names which have been given 

 to the various constituents of steel, many of which are not phases, and 

 do not find a place in the equilibrium diagram. He does not agree to 

 the proposed abandonment of the names troostite, osmondite, sorl)ite, 

 etc. None of the terms which have come into use should be omitted 

 from a hst of definitions. 



Burgess, G. K. — Metallography and Metallurgy at the Bureau of Standards. 



Met. and Chem. Engineering, x. (1912) pp. 467-8. 



Campbell, W., & H. B. Allen — Heat-treatment of a Nickel Steel. 



School of Miyies Quarterly, xxxiii. (1911) pp. 72-83. 



* Zeitschr. Anorg. Chem., Ixxv. (1912) pp. 145-59 (5 figs.), 

 t Met. and Chem. Engineering, x. (1912) pp. 205-7 (9 figs.). 

 X Met. and Chem. Engineering, x. (1912) pp. 23-6. 



