434 Si r Humphry Davy on the magnetic phenomena 
vided the wires were kept cool, whether the mass was a single 
wire, or composed of 6 of the smaller wires in contact with 
each other. This result alone showed, that surface had no re- 
lation to conducting power, at least for electricity of this kind, 
and it was more distinctly proved by a direct experiment; 
equal lengths and equal weights of wire of platinum, one 
round, and one flattened by being passed transversely through 
rollers so as to have six or seven times the surface, were 
compared as to conducting powers : the flattened wire was 
the best conductor in air from its greater cooling powers, but 
in water no difference could be perceived between them. 
VI. I tried to make a comparison between the conducting 
powers of fluid menstrua and charcoal and those of metals. 
Six inches of platinum foil, an inch and i broad, were placed 
in a vessel which could be filled with any saline solution ; and 
a similar piece of platinum placed opposite at an inch distance ; 
the whole was then made part of a voltaic circuit, which had 
likewise another termination by silver wires in water ; and 
solution of salts added, till gas ceased to be liberated from 
the negative silver wire. In several trials of this kind it 
was found that the whole of the surface of six inches, 
even with the strongest solutions of common salt, was 
insufficient to carry off the electricity even of two pair 
of plates; and a strong solution of potassa carried off' the 
electricity of three pair of plates only; whereas an inch of 
wire of platinum of (as has been stated) carried off all 
the electricity of 6 o pair of plates. The gas liberated upon 
the surface of the metals when they are placed in fluids, 
renders it impossible to gain accurate results ; but the con- 
ducting power of the best fluid conductors, it seems probable 
