ELECTRICITY, MAGNETISM, AND OBAVITATION. 



157 



warmth to the air, ignite a second fire, or boil water, which 

 shall absorb just the exact amount of heat lost by the heated 

 iron, and shall ultimately be able to retain this communi- 

 cated caloric for a considerable period ? 



I think that heat is shewn, by these and other facts, to 

 have an independent existence, so far as our present ideas of 

 entity and non-entity extend. 



Agib, if caloric were admitted to be the mere creation of 

 matter, how is it that the other imponderable forces, which 

 are by many philosophers admitted as convertible into caloric, 

 and vice versa, are not by them also assigned to the same 

 origin and the same mode of existence ? 



It has already been shewn by the labours of Dr. Wollaston, 

 Dr. Faraday, and the author of this paper, that the ordi- 

 nary electric and voltaic forces are identical ; and many years 

 ago the analogy of aerial electricity, or lightning, was suffi- 

 ciently demonstrated by the experiments of Dr. Franklin. 



The reciprocal influence and mutual dependence of these 

 forces along with magnetism, and the obedience of electricity 

 to some of the laws of magnetism, and vice versa, as well as 

 the analogy of the phenomena manifested by all these forces, 

 evince their identity. In illustration of the identity of 

 electricity with magnetism, T read a paper before the British 

 Association in 1842, in which it was shewn that a plate of 

 glass maintained in a constant polar condition by the simple 

 current from the ordinary electrical machine, sustained the 

 weight of 5 oz. and 20 grs.; shewing that frictional elec- 

 tricity itself, when placed in a condition resembling mag- 

 netism — or rather electro-magnetism — will produce with them 

 an equivalent effect proportionate to its inferior quantity and 

 powers. 



With regard to the identity of light and heat— forces 

 which 1 hold to be so far identical as to be in their common 

 acceptation simply the essential qualifies of the one subtile 



