metallic substances as conductors of electricity . 23 
heated by an electrical explosion as much as iron. In accord- 
ance with this fact, it was found that wires drawn from some 
foreign gold coins, said to be very pure, were much worse 
conductors of electricity, than when drawn from the same 
previously refined. 
I did not find the conducting power to be influenced by 
any new disposition or arrangement of the quantity of metal ; 
thus, whether the metallic wire was perfectly cylindrical, 
flattened into a ribbon, or separated into four smaller wires, 
the effect produced was in each case alike. 
The influence of a small portion of alloy on the conducting 
power renders it necessary to have the metals pure, and I 
have reason to believe that the specimens, which were in these 
instances made the subjects of experiment, were as nearly so 
as possible. 
The alloys were prepared by fusing the metals together 
with a common blow-pipe on a charcoal support, having pre- 
viously weighed the relative proportions ; after which the 
small button of metal was again weighed and drawn into 
wire. I am not aware that this method of forming alloys with 
small quantities of metal is liable to any material error. 
The wires operated on in the course of this investigation 
varied from the ^th to the ^th of an inch in diameter, 
below which it was not found desirable to reduce them. 
