596 SUMMARY OF CURRENT RESEARCHES. 



matters can be readily arranged so that each mould is poured at the 

 correct heat. In determining this correct heat, experience must, until 

 a very considerable advance has been in pyrometer methods, be the only 

 guide. Empirical though this may be, when carefully applied regularly 

 successful results follow. 



Structure of Metals.* — J. A. Ewing, in the Rede lecture, deals with 

 the insight into the structure of metals as yielded by metallographic 

 methods of research. He showed by lantern projection how the crystal- 

 line nature of metals could be observed, and pointed out how stress pro- 

 duced slip-lines among the crystals. This was of great practical interest 

 in connection with " fatigue " in metals, which was shown to be due 

 first to slips appearing on isolated grains, and then to the development 

 of these slips into cracks. He dealt at length with binary alloys and 

 eutectics, giving it as his opinion that the formation of a eutectic 

 occurred by alternate surfusion or supersaturation of each constituent 

 in the other. Eutectics in which the constituents were not of the same 

 crystalline system appeared to be mechanically weak. The properties 

 connected with recalescence were illustrated by experiments on a steel 

 wire coiled into the form of a spring, and carrying a light weight. The 

 spring extended in a conspicuous way while the process of re-crystallisa- 

 tion associated with recalescence was going on. The gradual changes of 

 structure which go on even at atmospheric temperature in lead and other 

 metals after the structure has been broken up by severe straining were 

 next described, and, in conclusion, the lecturer referred to the analogous 

 case of glacier-ice, which had for long been known to possess a granular 

 structure, each grain being a crystal, just as in the case of metals. 

 Photographs by Principal Skinner, illustrating this granular structure, 

 were shown. In the upper neve the grains were vague and comparatively 

 small ; as the glacier slowly travelled down, the grains became consoli- 

 dated and large, and their outlines became well defined. Clearly a slow 

 process of crystal growth was going on, and it was to this very process 

 of growth that the plasticity of the glacier as a whole was to be ascribed. 

 Nothing was more striking to a worker in this field than the evidence 

 to be found that those substances on which we were most accustomed 

 to rely as constant were undergoing, sometimes comparatively fast and 

 sometimes very slowly, a process of internal flux. A monument more 

 enduring than brass might be a lofty ideal, but it was seen at least to be 

 an ideal easy of conception when one realised how far from constant the 

 inner structure of brass and other metals was apt to be. 



Boynton, H. C. — Troostile. Iron and Steel Mag., vii. (June 1904) 



pp. 606-28 (22 figs.). 

 Hofman, H. O., Gkeen, C. F., & Yerxa, K. B. — Laboratory study of the stages 

 in the Refining of copper. 



[Micrographic studies of a number of copper samples in different stages were 

 made ; full statistics are given.] 



Technology Quarterly and Proc. of Soc. Arts, xvii. (March 1904) 

 pp. 76-100 (6 tables of statistics, 31 figs.). 



Johns, C. — Notes on the production and thermal treatment of steel in large masses. 



Iron and Steel Mag., vii. (June 1904) pp. 596-606 (7 figs.). 



* Abstract of Rede lecture before the University of Cambridge, June 11, 1904 ; 

 and Nature, 1808 (June 23, 1904), pp. 187-8. 



