ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 369 



Metallography, etc. 



Structure of Ternary Alloys.* — Gr. H. Gulliver points out and 

 explains a diiference in structure between a binary eutectic occurring 

 in a binary alloy, and a binary eutectic occurring in a ternary alloy when 

 a ternary eutectic is also present. In a solidifying binary alloy primary 

 crystals are surrounded by liquid during their gradual growth, and thus 

 become relatively large, while the eutectic, solidifying at a constant 

 temperature, has a relatively much finer structure. But the solidifica- 

 tion of a binary eutectic separating from a ternary alloy takes place 

 throughout a range of temperature, and liquid is always present. The 

 crystals of which this binary eutectic is composed are thus enabled to 

 grow to a considerable size. It is shown that the bismuth-tin eutectic 

 in a lead-bismuth tin alloy consists of well-formed crystals of each 

 metal. The ternary eutectic solidifies at a constant temperature and 

 has accordingly a fine structure. 



Magnesium-cadmium Alloys.j — G. G. Urasow confirms by micro- 

 scopical examination of these alloys the conclusions drawn from a study 

 of their hardness and electrical conductivity, and from thermal analysis. 

 The sections were etched with water. At the ordinary temperature two 

 series of solid solutions exist, (1) of the compound /?-CdMg, (2) of 

 a-Cd Mg, in their components. 



Ternary System Copper-silver-gold. |— E. Janecke has determined 

 the equilibrium diagram by thermal methods, and confirmed it by 

 microscopical examination of numerous alloys. The majority of the 

 alloys contained only one constituent, a homogeneous solid solution 

 The remainder contained the eutectic composed of two ternary solid 

 solutions ; this may be regarded as the copper-silver eutectic with gold 

 present in soUd solution in each phase. The eutectiferous alloys were 

 readily etched with dilute nitric acid, while long etching with aqua regia 

 was necessary for some of the other alloys. 



Life-history of Cells and Grains in Steel. § — H. M. Howe sharply 

 distinguishes " grains " from " cells " as structural forms in steel. The 

 individual islets of ferrite or cementite are grains, while the cells con- 

 sist of envelopes of ferrite or cementite, containing kernels of pearlite 

 intermixed with or replaced by other constituents. Grain-size and cell- 

 size increase with increase of temperature and time of heating above 

 the critical range. The effect of high and long heating in coarsening 

 the cell-size represents the coarsening of the austenite grains during 

 that high heating, each such grain being later represented by a single 

 cell. The effects of high temperatures and of different rates of cooling 

 upon the form assumed by the ferrite, are described and explained. 



* Proc. Eoy. Soc, Edin., xxxii. (1912) pp. 3G-9 (2 figs.), 

 t Zeitschr. Anorg. Chem., Ixxiii. (1911) pp. 31-47 (14 figs.), 

 i Metallurgie, viii. (1911) pp. 597-606 (27 figs.). 

 § Int. Journ. Metallogra-hy, ii. (1911) pp. 13-25 (11 figs.). 



