95 
CuSn 
©) 2 6 @ 5 Sn 
Percenfage of Copper 
Part of Provisional Copper -Anfimony -Tin Diagram, 
Fig. 3 
Fig. 1. e-tin-copper also is hard, has a lower specific gravity than that of 
tin and forms first of all crystals of the alloy of this composition, on a fall- 
ing temperature, along the branch E-F of the liquidus of Fig. 2. 
These crystals grow rapidly at temperatures within their formation 
ranges. On account of their relatively low specific gravities flotation in the 
still liquid portions readily occurs. It may easily happen that a given bear- 
ing may have its hard, wear-resisting components so large that they become 
broken in use and so distributed as to possess quite different properties at 
different points. Figs. 4, 5, 6, 7 and 8 illustrate the rapidity of flotation.* 
Metal was melted and immediately poured on a warm iron plate. A sheet 
about one-fourth inch in thickness solidified in less than thirty seconds. 
Figs. 4, 5, 6 and 7 show the cast, unpolished upper surface, Fig. 8 the lower 
surface, polished and etched with nitric acid. Even in the short time that 
elapsed between pouring and solidification, segregation of -crystals has 
occurred to so great an extent that none at all are present in the lower 
surface layer. Figs. 9 and 10 illustrate the extent of growth under unusual 
conditions, although it may be noted that such conditions might easily be 
brought about by inadequate control of furnace conditions. 
Rapid growth and segregation at higher temperatures are well recognized 
phenomena. In the experiments described in this paper an attempt was 
made to determine the relative rates of growth and segregation of the two 
systems of crystals here mentioned, in temperature ranges near the re- 
spective solidi. 
Working specimens were first prepared by melting a quantity of the 
alloy at 650° C., stirring thoroughly with a stick of wood and immediately 
casting in chill molds of cast iron. This resulted in the formation of fine 
crystals, as shown in Figs. 11 and 12, taken after polishing and etching 
sections of two of the pieces. These specimens were then heated to stated 
temperatures and either chilled or slowly cooled after certain periods of 
