544 SUMMARY OF CURRENT RESEARCHES. 



Growth of G-rain in Metals and Alloys.* — F. Robin gives a more 

 extended account of the work previously summarized.t Crystal growth, 

 and in particular the development of abnormally large crystals by the 

 annealing of cold -worked specimens, has been studied in tin, lead, zinc, 

 aluminium, copper, and iron, and in numerous binary alloys of these 

 metals with other metals. While great irregularities in the rate of 

 growth of crystals were observed, it would appear that when a uniformly 

 cold-worked metal is annealed at different temperatures, large grains are 

 obtained at the temperature at which annealing begins, and also at a 

 temperature just below the melting-point, a minimum grain-growth 

 occurring at some intermediate temperature. Deformed crystals have a 

 remarkable capacity for growth when annealed, and appear to grow most 

 readily at the expense of neighbouring undeformed crystals. Solid 

 solutions resemble pure metals in their development of crystallization on 

 annealing, but do not as a rule show such rapid growth of crystals as 

 pure metals. 



Microscopic Examination of Coal.J — A. Wahl and P. Bagard have 

 applied metallographic methods to the investigation of the constitution 

 of coal. After plain polishing or polishing in relief no structure was 

 visible. Immersion in warm pyridine, for a length of time depending 

 on the character of the coal, developed a distinct banded structure in 

 some of the polished specimens. The method appears to be capable of 

 yielding information as to the degree of homogeneity of certain coals. 



♦ Rev. M6tallurgie, x. (1913) pp. 722-68 (48 figs.). 



t See this Journal, 1913, p. 109. 



i Comptes Rendus, clvii. (1913) pp. 380-1 (2 figs.). 



