METALLIC WIRES BY ELECTRICITY. 471 
a battery, close to an air thermometer, an interruption of the 
circuit was made and two small plates of brass introduced par- 
allel and opposite to each other. The plates were first placed 
at one-tenth of a line and then at one line apart from each other. 
Similar discharges produced an increase of temperature in” the 
thermometer, for the most part not less and sometimes greater 
in the latter position of the plates than in the former. Although 
in the more distant plates the discharge took place with a less 
quantity of electricity than when they were placed nearer to each 
other, the more complete condensation of the electricity on the 
edges of the plates completely compensated the diminished effect 
upon the temperature from the former cause. 
After what has been stated, the discontinuous discharge of 
large quantities of electricity through continuous wires can no 
longer be doubted. The partial fusion of the wires, the common 
occurrence of their splitting to pieces in the direction of their 
axis, and the remarkable bends which appear previous to incan- 
descence, afford clear additional proof of this manner of dis- 
charge ; whilst, on the other hand, with smaller quantities of 
electricity, the like increase of temperature in every similar seg- 
ment of the wire most indisputably establishes the continuous 
propagation of the discharge. To present a clear idea of the 
action of an electrical discharge upon a wire, we must therefore 
express ourselves in the following manner :— 
Electrical discharges, up to a certain degree of intensity, are 
propagated continuously through every wire; causing the wire to 
become warm and magnetic ; more powerful discharges propagate 
themselves through the wire only in a discontinuous manner, the 
results of which are the bends, incandescence, the tearing to 
pieces, the fusion and reduction to powder of the wire. 
Different Modes of Propagation of the Discharge in Fluids. 
The different modes of propagation of the electrical discharge in 
one and the same medium are by no means confined to the metals; 
they are so striking in imperfect conductors of electricity that they 
could not be overlooked. Faraday * adopts four different modes 
of electrical discharge through the air, which he distinguishes 
by their attendant luminous appearances and mechanical effects, 
* Experimental Researches in Electricity, London, 1839. 
