43° Sir Humphry Davy on the magnetic phenomena 
dent circuit from the ends of the battery with silver wires in 
water, so that the chemical decomposition of the water indi- 
cated a residuum of electricity in the battery. Operating in 
this way, I found that an inch of wire of platinum of —q, kept 
cool by water, left a great residual charge of electricity in a 
combination of twelve batteries of the same kind as those 
above mentioned ; and after making several trials, I found 
that it was barely adequate to discharge six batteries. 
V. Having determined that there was a limit to the quantity 
of electricity which wires were capable of transmitting, it be- 
came easy to institute experiments on the different conducting 
powers of different metallic substances, and on the relation 
of this power to the temperature, mass, surface, or length of 
the conducting body, and to the conditions of electro-magnetic 
action. 
These experiments were made as nearly as possible under 
the same circumstances, the same connecting copper wires 
being used in all cases, their diameter being more than one- 
tenth of an inch, and the contact being always preserved per- 
fect ; and parts of the same solutions of acid and water were 
employed in the different batteries, and the same silver wires 
and broken circuit with water were employed in the different 
trials ; and when no globules of gas were observed upon the 
negative silver wire of the second circuit, it was concluded 
that the metallic conducting chain, or the primary circuit, was 
adequate to the discharge of the combination. To describe 
more minutely ail the precautions observed, would be tedious 
to those persons who are accustomed to experiments with the 
voltaic apparatus, and unintelligible to others ; and after all. 
