172 



Messrs. C. T. Hey cock and F. H. Neville 



It may be remarked that the freezing-point curve forms a useful 

 chart to the general character of the alloys. For example, alloys 

 whose composition lies in the region AB of the figure are red bronzes 

 and gan metals, tough, but not very hard, while as we approach C 

 the alloys become paler in colour and much harder. Alloys a little to 

 the left of G are nearly white and extremely tough and strong ; they 

 are ideal bell metals. The moment we pass C the alloys begin to 

 become brittle, and the brittleness becomes very great near D. The 

 alloys between C and D are steel coloured ; they have a glass-like 



Fig. 1. — -Freezing-point curve of the copper-tin alloys. Atomic percentages of tin 

 are reckoned from per cent, on left to 100 per cent, on right of diagram. 

 (Extracted from ' Phil. Trans.,' A, vol 189, p. 63.) 



hardness and take a fine polish ; they are speculum metals, Lord Rosse's 

 being the alloy at D. With more tin than that present at the point D 

 the alloys deteriorate from a mechanical point of view, and except as 

 anti-friction metals are not much used, 



In 1900 we commenced a study of these alloys by means of the 

 microscope. As regards the regions ABC and that to the right of E 

 we at first did little more than confirm results which we found had 

 been already published both by Mr. Stead and by M. Charpy ; but in 

 the region CDE we appear to have observed more detail than is con- 

 tained in the published work of these observers. We were especially 

 struck by a discrepancy, in the region CD, between the crystals on 

 the outside of the alloys and the internal pattern. Our habit was to 



