118 Mr. M. Donovan on the supposed Identity of the Agent 



The compound nature of the electricity which appears in the 

 phenomena called galvanic has been often suspected, and the 

 difficulty of explaining them without some such admission has 

 been felt. Dr. Davy asks — "May we suppose, according to the 

 analogy of the solar ray, that the electrical power, whether excited 

 by the common machine, or by the voltaic battery, or by the 

 torpedo, is not a simple power, but a combination of powers, 

 which may occur variously associated, and produce all the varie- 

 ties of electricity with which we are acquainted*?" Sir H. Davy 

 believed that the current of a voltaic series is a mixture of mag- 

 netism and electricity f. Professor Hare conceives that the fluid 

 extricated in the voltaic series is a combination of electricity, 

 caloric and light J. There are other conjectures which need not 

 be here particularly noticed. 



That the electric fluid contains heat is clearly proved by its 

 power of fusing metals, and setting fire to various combustibles. 

 That these phenomena are due to the presence of the principle 

 called caloric can scarcely be doubted ; the same that is evolved in 

 ordinary cases of combustion, attrition, combination, and other 

 manifestations. If it be not so, we must no longer speak of caloric 

 as the principle which, by addition and subtraction, causes the 

 sensations and phenomena of heat and cold : we must admit two 

 calorics ; and if so, why not as many other kinds as there are 

 different sources ? There is no advantage in supposing that the 

 heat is extricated from the matter acted on by the electric fluid. 



That light is contained in the electric fluid is rendered obvious 

 by many beautiful contrivances ; and that it is common light is 

 evident from experiments made on its refraction, reflexion, po- 

 larization, absorption and decomposition. Were it denied that 

 electric light is the same as ordinary light, it should be admitted 

 as a consequence that all luminous phsenomena are not attribu- 

 table to the old well-known element, but that there are other 

 principles in nature created to exercise one and the same func- 

 tion, which is improbable. 



The existence of magnetism in the electric fire is rendered 

 probable by those experiments in which steel has been magnet- 

 ized by explosion of a Leyden jar, and the poles of magnetic 

 needles have been reversed. But there is direct evidence of its 

 presence in the arch of flame which Sir H. Davy obtained from 

 the terminal charcoal points of a voltaic battery ; there was even 

 undoubted proof of what may be called a current of magnetism ; 

 for by means of a powerful magnet, the arch of flame could be 

 attracted or repelled according to the pole of the magnet applied. 

 This fact, suspected by Arago, was proved by De la Rive and 



* Philosophical Transactions, 1832, p. 275. 



t Phil. Mag. S. 1. vol. lviii. p. 415. % Ibid, 1821, pp. 286, 293. 



