ON THE ALLOYS OF COPPER AND ZINC. 39 
the sheets of alloy in such a manner that no fibres could form in them, and that 
their structure should be homogeneous. 
Bobierre, in his very able thesis, to which I have already alluded, has urged that 
it would be well to discontinue the use of the alloy containing 60 per cent of copper, 
which admits of being rolled hot, and to substitute for it sheathing prepared from 
alloys containing about 66 per cent of copper, which can only be prepared by a 
most laborious process of cold rolling. It is true that the fibres which I have 
described would in this case probably never be encountered. Still there are several 
important objections to the proposition of M. Bobierre. Not only would the method 
of cold rolling consume a much greater amount of time and labor; but it would 
be exceedingly difficult, if not impossible, to procure any alloy the composition 
of which could be maintained so nearly constant as is the case with yellow-metal.* 
It is not probable that a test like the one applied to this alloy could be found 
anywhere else in the whole series. 
It is frequently stated in chemical text-books that yellow-metal is always prepared 
from “ best-selected” copper, and one is led to infer that a metal of peculiar purity 
is alone used in its manufacture. This may once have been the case; but since 
the immense increase in the use of this alloy, it would no longer be practicable 
to obtain a sufficient quantity of copper of uniform character, or indeed of any one 
kind, from which to prepare the large quantity of sheathing which is used. In an 
establishment where expense would be a secondary consideration, as, for example, 
in a government workshop, it might still be possible to prepare an alloy constantly 
from the same sorts of copper and of zinc, in which case, although the amount of 
zinc lost would probably be subject to considerable variations, one might, nevertheless, 
soon be able to control the process, and to prepare an alloy of the composition 
proposed by Bobierre, so that only trifling variations should occur in the composition 
of the product. But in ordinary practice manufacturers are compelled to make 
use of the most varied kinds of copper, not only because the supply of the best 
sorts is limited, but particularly from the fact, that, owing to the competition 
which exists between the various founderies, — or rather, by force of the laws which 
regulate supply and demand,— they are obliged to remelt larger quantities of 
old copper sheathing,t the origin of which is unknown to them, and which may 
have been originally prepared from copper of inferior quality. 
* An alloy of constant composition might, however, possibly be prepared, by adding known quantities 
of melted copper to determined volumes of molten yellow-metal which had been prepared by the usual method. 
+ The popular notion, that a better — “more compact” — product is obtained by remelting any alloy, 
may also have some connection with this custom. 
