ON THE ALLOYS OF COPPER AND ZINC. 95 
and then pounding it in an iron mortar till it is reduced to a somewhat coarse powder. 
With the fibres, this result is easily obtained, since no great effort is necessary to 
tear asunder the numberless little crystals of which they are composed; but the larger 
individual crystals which occur in the crust and core, as just described, are much more 
refractory; they are removed from the finer powder by sifting, and are subsequently 
remelted. Among these rejected * kernels" very good crystals may often be found. 
The tendency to shoot out into fibres, which has been alluded to, and which 
deserves something more than a passing notice, extends over quite a space, from 
alloys containing 57 or 58 per cent of copper, or even more, down to those containing 
49 or 44 per cent, where it gradually disappears, as I have proved by casting a series 
of ingots. Although it does not altogether prevent one from obtaining crystals 
by the method of pouring off the still fluid portion of the alloy from that which 
has been allowed to solidify, still the crystals which I have obtained in this way 
within the limits of its influence are in general less perfect than those of the 
alloys containing more copper; indeed, on remelting the solder from which the 
finest separate crystals were obtained, and pouring off a portion of it after the 
rest had become solid, only indifferently good specimens could be procured. The 
alloy appearing to pass so quickly from the liquid to the solid state, that the crystals 
have but little time in which to form. It is remarkable that this inclination to 
form fibres is strongest in those alloys which contain nearly equal equivalents 
of zinc and copper, being less clearly marked as one recedes in either direction 
from this point, until a stringy texture analogous to that of copper is reached on 
the one hand, and the peculiar pastiness of zinc on the other. In preparing crystals, 
this pastiness manifests itself decidedly in the alloys immediately below those 
which are fibrous, becoming more strongly marked as the alloys are richer in 
zinc;—at least, so far as my own experiments have extended, i. e. to 30 per cent or 
less of copper. The fracture of these white alloys is for the most part vitreous. 
The pasty condition appears to depend to a certain extent on the manner in which 
the alloy is cooled, being less apparent when this process has been rapid. I have 
repeatedly obtained fine cups lined with tolerable crystals from alloys, which in other 
trials afforded nothing but a mass of paste. The transition, however, from com- 
plete liquidity to the pasty condition, when the latter is assumed, is very rapid. 
'The fact that the alloys just mentioned take on the fibrous texture when cooled 
under ordinary circumstances has, moreover, a very important practical bearing ; — 
alloys at the upper limit of this fibrous tendency being the lowest—i. e. richest 
in zinc — which can be rolled or subjected to the various processes by which metals 
