ZOOLOGY AND BOTANY, .MICROSCOPY, ETC. 713 



Changes occurring in Nickel Steel.*: — C. E. Guillaume has inves- 

 tigated the length changes taking place in course of time in high-nickel 



steels. Steels containing 28—42 p.c. nickel expand slightly on keeping, 

 while those with higher nickel content, up to 70 p.c, contract. Previous 

 heating, by accelerating the transformations corresponding to these 

 volume changes, reduces the amount of the subsequent alterations. The 

 advantages offered by the 42 p.c. and 56 p.c. alloys for the construction 

 of length standards are discussed. 



Ovifak Iron.f — C. Benedicks has microscopically examined speci- 

 mens of the mass of iron, weighing 25,000 kilograms, found at Ovifak, 

 in order to determine if it is of meteoric origin. The iron was found to 

 contain 1*6 p.c. carbon and some sulphur. The chief constituents are 

 free cementite and pearlite, which by its fine structure would indicate 

 that the iron cannot have been cooled slowly below 700" C. A structure 

 formed of alternate lamellae of cementite and iron oxide is termed 

 " oxide-pearlite." This mass of natural steel has probably been formed 

 by the reduction of iron compounds in molten basalt by carbonaceous 

 matter. 



Cementation of Alloy Steels.} — F. Giolitti and F. Carnevali have 

 carbonized nickel steels containing 2-30 p.c. nickel, and a chromium 

 steel containing 2 '3 p.c. chromium, with ethylene and with carbon 

 monoxide, at 950° and at 1050° C. The phenomena of cementation 

 were in general the same as those observed with carbon steels, but in the 

 nickel steels the maximum content of carbon in the cementation zone 

 diminished with increase of nickel content, while the presence of chromium 

 raised the maximum carbon content. The eutectoid composition of steels 

 containing 2-5 p.c. nickel appears to be 0* 6-0 "65 p.c. carbon. 



F. Giolitti and G. Tavanti have studied the cementation of nickel 

 steels containing 20-50 p.c. nickel. 



Structure of Galvanized Iron.§ — W, Guertler has investigated the 

 microstructure of galvanized iron manufactured by the three usual 

 methods : the dipping process, sherardization, and the electrolytic pro- 

 cess. In all cases, a layer of crystals of the compound FeZn 3 is present 

 between the iron and the zinc coating, but in material zinc-coated elec- 

 trolytically, this layer of FeZn 3 is much thinner than in dipped or 

 sherardized specimens. The FeZn 3 layer is electro-negative to both iron 

 and zinc, and accordingly accelerates corrosion when exposed. The zinc 

 coating obtained by dipping always contains crystals of about the com- 

 position FeZn 7 , also electro-negative to zinc. Various other structural 

 features of galvanized iron characterizing the different processes of 

 manufacture are described. 



Welding up of Blowholes and Cavities in Steel Ingots. || — J. E. 

 Stead defines welding as the crystallizing into union of two solid metallic 



* Gomptes Rendus, cliii. (1911) pp. 156-60 (1 fig.). 

 t Metallurgie, viii. (1911) pp. 65-8 (8 figs.). 



J Atti R. Accad. Sci. Torino, xlvi. (1911) pp. 409-32, 558-68. Rass. Min. Met. 

 e Chim., xxxiv. (1911) through Journ. Soc. Chem. Ind., xxx. (1911) p. 1017. 

 § Int. Zeitschr. Metallographie, i. (1911) pp. 353-76 (18 figs.). 

 li ;journ. Iron and Steel Inst., lxxxiii. (1911) pp. 54-102 (10 figs.). 



