190 
of the electric fluid ? For why should oxygen gas 
be thus essential to the development of electricity, 
if it be not chemically instrumental in affording elec- 
tric matter ? and in what other way can it, in these 
experiments, be conceived to afford such matter, ex- 
cept by suffering that reduction of its elasticity, 
which it has been shewn to undergo ? If the air were 
only mechanically concerned, and acted simply as a 
conducting body, or, if the electricity were excited 
only by friction, then no reason appears why oxygen 
gas should be thus essential to the operation, and 
much less why it should undergo such chemical 
changes ; for, that these changes are necessary, is 
proved by the fact, that even oxygen gas itself is un- 
equal to the production of electricity, if a metallic 
substance, incapable of oxidation, be employed as an 
amalgam. Surely the conversion of zinc into an 
oxide by combustion in oxygen, does not furnish any 
other or better evidence of the extrication of caloric 
from that gas, than the formation of a similar oxide 
in electrization affords of the development of elec- 
tric matter from the same gas, in the experiment of 
Dr Wollaston. In both cases, the subtile matter is 
not simply conducted by the air, but is generated out 
of it ; and, in both cases, therefore, its production 
must be the consequence, and not the cause, of oxi- 
dation. 
461. But while, in these examples, we attribute 
the production of electric matter to the chemical ac- 
tion of oxidation, we do not mean to say that this is 
the only, or even the usual way, in which electricity 
is developed. The experiments of various philoso- 
