428 Sir Humphry Davy on the magnetic phcenomena 
pended entirely upon the magnetism, and not upon the elec- 
trical inductive power of the magnet, for masses of soft iron, 
or of other metals, produced no effect. 
The electrical arc or column of flame was more easily af- 
fected by the magnet, and its motion was more rapid when it 
passed through dense than through rarified air ; and in this 
case, the conducting medium or chain of aeriform particles 
was much shorter. 
I tried to gain similar results with currents of common 
electricity sent through flame, and in vacuo. They were al- 
ways affected by the magnet ; but it was not possible to obtain 
so decided a result as with voltaic electricity, because the 
magnet itself became electrical by induction, and that whether 
it was insulated, or connected with the ground.* 
IV. Metals, it is well known, readily transmit large quanti- 
ties of electricity ; and the obvious limit to the quantity which 
they are capable of transmitting seems to be their fusibility, 
or volatilization by the heat which electricity produces in its 
passage through bodies. 
Now I had found in several experiments, that the intensity 
of this heat was connected with the nature of the medium by 
which the body was surrounded ; thus a wire of platinum 
which was readily fused by transmitting the charge from a vol- 
taic battery in the exhausted receiver of an air pump, acquired 
in air a much lower degree of temperature. Reasoning on 
* I made several experiments on the effects of currents of electricity simultaneously 
passing through air in different states of rarefaction in the same and different direc- 
tions, both from the voltaic and common electrical batteries ; but I could not es- 
tablish the fact of their magnetic attractions or repulsions with regard to each other, 
which probably was owing to the impossibility of bringing them sufficiently near. 
