mineral species independent of the Phenomena of Isomorphism, 407 
On increasing gradually the amount of zine in the alloy up 
to 48°7, the crystals continued to have the composition of the 
alloy ; and the only difference which could be observed in their 
character was that they were smaller, and more frequently 
isolated. Between these limits the whole mass of the alloy ex- 
hibited a strong tendency to crystallization ; and by pouring it, 
as it cooled, from one vessel to another, it could be crystallized 
to the last drop. On increasing the amount of zinc in the alloy 
to 50°7 per cent., the amount of zinc found in the crystals was 
uniformly less than it was in the alloy; but no closer relation 
between the two could be detected, owing, undoubtedly, to the 
unavoidable irregularity in the crystallization of the alloys which | 
contained more than 50 per cent. of zinc. This arose from a 
peculiar pasty condition which the liquid mass assumed at the 
point of crystallization. Definite crystals, however, were ob- 
tained from an alloy of 60 per cent. zine containing 55 per 
cent.; above this the crystals became less and less abundant, 
and gradually faded out, although the alloy of 86 per cent. of 
zine exhibited a radiated crystalline texture; and a trace of this 
structure could still be discovered even in the alloy containing 
only 4 per cent. of antimony. It was very interesting to tracé 
the gradual fading out of the crystalline structure, as the cha- 
racter of the phenomenon was entirely analogous to that which 
may be noticed in many crystalline rocks. 
Finding that the crystalline form of Sb Zn® was constant undet' 
so great an increase of the proportion of zinc in the crystals, it 
might be supposed that, on returning to the alloy of 42°8 per 
cent. of zinc and increasing the amount of antimony, we should 
obtain crystals containing an excess of antimony ; but so far is 
this from being true, that the slightest excess of antimony en- 
tirely changes the character of the crystallization. On crystal- 
lizing an alloy containing 41°8 per cent. of zinc, not a trace of 
any prismatic crystals could be seen; but in their place there 
was found a confused mass of thin metallic scales, which, as will 
soon be shown, are imperfect crystals of Sb Zn®. Thus it appears 
that, although perfectly formed crystals of Sb Zn? can be obtained 
containing 55 per cent. of zine (that is, 12 per cent. above the 
typical proportions), they cannot be made to take up the slight- 
est excess of antimony. 
Let us pass now to the crystals of Sb Zn*. In order to obtain 
crystals having the exact typical constitution, it was found ne- 
cessary to crystallize an alloy containing not more than 31°5 per 
cent. of zinc. At this point large compound crystals are obtained. 
corresponding to the large crystals of Sb Zn®; and the same was 
true of alloys down to 27 per cent. of zinc. Between these two 
limits (namely, alloys of 31-5 and 27 per cent. of zinc) the ery- 
2EK2 
