ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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isomorplious mixtures with each other. These alloys, whatever may be 
their composition, consist of only one species of crystals, which fill the 
whole space, the composition and the properties of the alloys usually 
varying in a continuous manner in each crystal. The number of metals 
capable of forming isomorplious mixtures with each other is small, the 
bismuth-antimony alloys being the only ones out of fourteen series in- 
vestigated by M. Charpy in which this property was found to exist ; but, 
on the other hand, there are many cases of definite compounds of two 
metals isomorphous with one of them. Thus, for example, microscopic 
study has enabled M. Charpy to detect a compound of tin and antimony 
containing about 50 per cent, of tin and isomorphous with antimony, 
Fig. 12. Fig. 13. 
Alloy of tin, 75 per cent. : antimony, 25 per cent. Pure gold, x 1000 diameters. 
although the freezing-point curve, worked out by Roland-Gosselin, and 
consisting of three branches having their concavities upwards, and meet- 
ing in two angular points or maxima, gives no direct indication of the 
relation between these metals. 
“ In fig. 11, in which the alloy containing 10 per cent, of antimony is 
shown, the cubical crystals appear to consist of the 50 per cent, alloy set in 
a eutectic magma. Fig. 12 shows the alloy with 25 per cent, of antimony. 
As the proportion of antimony in the whole mass approaches 50 per cent., 
these crystals invade the whole field, and numerous minute cracks appear, 
on the edges of which is seen a secondary crystallisation without the 
interposition of an intermediate substance. This structure is character- 
istic of a pure or homogeneous substance, as in the beautiful micro-sec- 
