specific Gravity, and comparative JVear of Gold. 111 
half a grain to °f the same metal, then a very remarkable 
expansion took place, which seemed to be a peculiar effect 
of this compound alloy ; for, in the subsequent case, when the 
lead was reduced to ^ of a grain, the degree of expansion was 
much less. 
Bismuth, in its various properties, as I have several times had 
occasion to observe, very much resembles lead, in respect to the 
effects which it produces upon gold, excepting, that when 
employed singly, and in the proportion of T *-, it occasioned a 
contraction equal to ,31. But, in smaller quantities, and in 
conjunction with copper, it produced expansion, which became 
very considerable, when bismuth was added in the proportion of 
4 grains, or of half a grain, per ounce ; so that what has been 
already said concerning lead may here be repeated. 
~ of zinc caused the mass to contract ,09; but the vola- 
tility of this metal renders the results very uncertain. In the 
last article, nearly the whole of the 8 grains of zinc were 
volatilized. 
It is not necessary to make any remarks on the effects pro- 
duced by cobalt and nickel upon gold ; and, in respect to anti- 
mony, we may observe, that contraction was produced in the 
two first cases, but expansion in all the others. Indeed, from 
a general view of the Table it appears, that those metals which 
most readily render gold brittle, are those which have the 
greatest tendency to produce contraction, when added to gold 
in certain proportions. 
In some cases, the degree of expansion seems to increase with 
the proportion of copper ; but then it must be observed, that this 
increase of expansion is frequently much more considerable 
