160 Prof. A. de la Rive’s Memoir of 
tact alone, if not accompanied by chemical action, is not a 
source of electricity. The memoir in which he probes this 
question to the bottom is the last which he devoted to this 
department of electricity. In it, by means of a multitude of 
ingenious experiménts, he demonstrates that the presence of an 
electrolyte (that is to say, of a liquid which is at once a com- 
ound and a conductor of electricity) is indispensable. for the ' 
production of electricity in a voltaic couple ; he varies his ex- 
periments in a thousand ways, sometimes by exhausting the 
number of chemical compounds employed as electrolytes, some- 
times by the intervention of temperature or of other agents ; 
and he concludes by showing by general considerations the 
improbability of the existence of a force of contact. 
We may say that this last work, a precious supplement to 
the preceding ones, has. rendered perfectly evident the truth of 
the chemical theory. This theory, foreseen by Wollaston and 
Fabroni, but opposed by most of the physicists of the early 
part of the present century, had found a powerful argument in 
its favor in the beautiful experiments of the elder Becquerel 
upon the electricity developed by chemical actions. It was then 
(from 1825 to 1835) that, profiting by these experiments, and 
seeking, on my own part, to make others of the same kind 
although in a slightly diferent. direction, I published several 
memoirs to support and render more precise the chemical theory | 
of the voltaic pile. But I cannot but admit that we are in- 
debted to Faraday for having based this theory upon irrefutable 
proofs, not only by the great number and variety of his re- 
searches, but especially by his beautiful discovery of the definite 
decomposing action of the electric current—a discovery which 
established between the external chemical action of the voltaic 
pile and the chemical action which takes place in the interior of 
this apparatus, a relation so intimate that it is impossible not 
to see in the latter the cause of the former. | 
III. 
In 1831 ee discovered electrical manetion it is had 
most important, although perhaps not the m st brilliant of his 
- of the great French physicist upon the mutual attractions and 
repulsions veoh oh ia sa ets, Faraday was | 
by pS ideas which were rather x disputable and not very 
conformable to the principles of mechanics, to assume that an 
electric current must. ‘tum. round the pole of a magnet with 
sts 
