So, likewise, by using an amalgam of silver or of platina, 
which are not liable to be oxidated, he could obtain 
no electricity. An amalgam of tin, on the contrary, 
afforded a good degree of excitation. Zinc acted 
still better ; but the best amalgam was made with 
both tin and zinc, a mixture which is more easily 
oxidated than either metal separately. In farther 
proof of this position, he found, that, when he con- 
fined a small machine, with its cushion and conduc- 
tor, in a vessel of common air, electricity was exci- 
ted ; but when he substituted carbonic gas, the exci- 
tation was immediately destroyed j and again return- 
ed upon re-admission of atmospheric air. The oxi- 
dated metal of the rubber, adds Dr Wollaston, is al- 
ways negative, and so, likewise, in the Voltaic pile* 
the oxidated zinc is in the same state. From these 
facts, he concludes, that electricity, in the common 
machine, and in the Voltaic pile, originates from the 
same source ; and the pov/er of the latter, he adds, 
is now known to depend on oxidation *. 
460. But if, from the foregoing facts, it appear, that", 
in ordinary cases, oxygen gas is alike necessary to the 
development of caloric in combustion and to the excita- 
tion of electricity ; if, in each instance, this gas disap- 
pear, and its ponderable matter enter into a similarconi-k 
bination ; and if no caloric or electricity be developed 
unless these chemical changes take place, are we not 
constrained to believe, that the same subtile matter, 
which, during combustion, is exhibited in the form 
of caloric, appears, during electrization, in the guise 
Philos. Trans. 1810, p. 
