ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 117 



of small amounts of aluminium or magnesium, as de-oxidizers in remelting 

 the white metal, was found to be small. The effect of small additions 

 of arsenic to the bronzes was studied. 



Properties of Brass.* — W. v. Moellendorf points out that commer- 

 cial brass bars consist of the solid solutions a and (S in varying propor- 

 tions, and that as these two phases differ widely in their properties, the 

 properties of a brass depend upon the relative amounts of a and /? which 

 it contains. The structure and properties of four copper-zinc alloys 

 are described. 



Crystallization of a-Iron.f— M. Ziegler advances theories to account 

 for several familiar structural phenomena in steel, such as the localization 

 of scoriaceous inclusions in the ferrite and not in the pearlite, the ring- 

 form of the ferrite in medium-carbon steel, the effect of speed of cooling 

 on grain-size, and the occurrence of " ghosts." At a high temperature 

 in the cooling of steel crystals of y-iron containing carbon are formed, 

 and scoriaceous matter falls out of solution taking the form of envelopes 

 surrounding these crystals. At a lower temperature the y-iron solid 

 solution decomposes into a-iron and carbide of iron. As commonly 

 occurs when a body crystallizes from a solution, the a-iron forms upon 

 the foreign particles — the scoriaceous inclusions — which act as nuclei for 

 crystallization. Thus a final structure is produced in which the ferrite 

 exists as bands of some width, forming a network enclosing the pearlite 

 grains, while the scoriaceous inclusions run centrally as strings in the 

 ferrite bands, also forming a more or less complete network. Such a 

 structure is familiar in steel castings. In re-heated, forged, or rolled 

 material, this structure is modified by such treatment. The scoriaceous 

 matter is partially, but usually not completely, re-dissolved on heating to 

 a sufficiently high temperature, and separates out on cooling, as before, 

 in envelopes which are larger as the temperature of re-heating is higher. 

 Thus the mesh of the ferrite network formed upon the scoriaceous 

 inclusions is larger the higher the temperature of re-heating. " Ghosts " 

 were originally regions in which a large amount of ferrite had crystal- 

 lized upon scoriaceous matter. Subsequent re-heating is not sufficient 

 to bring about a complete diffusion of this ferrite into the surrounding- 

 steel, and the " ghost " is found in the finished piece as a region, usually 

 elongated by the forging, containing little carbon and a number of 

 scoriaceous inclusions embedded in ferrite. Explanations of the brittle- 

 ness of coarse-grained steel, of the effects of annealing and quenching, and 

 of the property of red-shortness, are suggested. The author's conclusions 

 are adequately illustrated by photomicrographs, 



Tschernoff Point h.X — A. Baboschin finds that no simple propor- 

 tionality exists between the grain-size of pearlite and the temperature, 

 in the range investigated, 700" to 1300° C. The curves obtained demon- 

 strate the existence of a critical temperature, above which grain-growth 

 is rapid. This tempei-ature — Tschernoff's point h — does not appear to, 

 coincide with Ar 3. 



♦ Stahl und Eisen, xxxi. (1911) pp. 325-6 (3 figs.), 

 t Rev. Metallurgie, viii. (1911) pp. 655-72 (22 figs.). 



X Journ. d. russ. met. Ges., 1911, pp. 89-100, through Stahl und Eisen, xxxi. 

 (1911) pp. 1061-2. 



