92 ON THE ALLOYS OF COPPER AND ZINC. 
I must observe in this connection, that G. Rose* has quite recently described 
a specimen of crystals, labelled * Mengepresse," — a term applied to an alloy prepared 
from one pound of copper from Lauterberg, and two pounds of calamine, — which 
exists in the Royal Mineralogical Museum at Berlin, having been obtained from 
the collection of Klaproth. These crystals, in the opinion of Rose, appear to 
belong to the monometric system; but since Prof. Rose has published no analysis of 
them, we not only have no clew to their probable quantitative composition, but 
are left in doubt whether they are really a compound of copper and zinc; though 
the facts which I have here brought forward render the supposition an extremely 
probable one. E 
Notwithstanding this, and in spite of the fact that his alloy is only a single 
isolated example, Rose has urged, in direct opposition to his previons opinion, that 
it proves that zinc must belong to the regular system. In point of fact, however, 
the observation of Rose, taken by itself, evidently proves nothing of the kind. For, 
admitting that his crystals are really brass, he has offered no evidence to show 
that they do not belong to one of several possible definite alloys ; only after proving 
that such crystals do occur through the whole series of alloys, as I have shown is 
really the case, and demonstrating that no definite compounds exist, could the idea of 
isomorphous mixture be entertained. 
The crystals obtained by myself vary in size; some of them being more than half 
an inch in length, while others are quite minute. In general they are smallest in 
those instances where the greater part of the alloy had solidified before the crust 
= was pierced. 
Fig. 1, which is a copy of a portion of the crystal- 
line crust, from the alloy containing 94.38 per cent 
of copper, may serve to give a general idea of the 
character of these crystals. | 
In a few of the specimens of alloys, the crystals 
have exhibited a tendency to assume a somewhat 
tabular form, — a single face of an octahedron being 
largely developed, to the exclusion of the other 
faces, as may be seen in Fig. 2, a; while in other 
specimens separate individual crystals have occurred, Fig. 2, b and c. Both of these 
peculiarities presented themselves in the alloy of 83.72 per cent of copper, portions - 
of which are represented in Fig. 2. 
* Pogg. Ann., July, 1859, CVII. 448. 
