752 LECTURE tX. 



riments, have however been in general too little supported by facts to be en- 

 titled to universal adoption. 



For some years past, the philosophical, as well as the unphilosophical world, 

 has been much occupied and entertained by the discoveries of Galvani, Volta, 

 and others, respecting the operations of the electric fluid. The first circum- 

 stance, that attracted Galvani's attention to the subject of animal electricity, 

 was the agitation of a frog, that had a nerve armed, that is, laid bare and co- 

 vered with a metal, when a spark was taken in its neighbourhood. A person 

 acquainted with the well known laws of induced electricity might easily 

 have foreseen tliis effect: it proved, however, that a frog so prepared was a 

 very delicate electrometer, and it led Galvani to further experiments. It has 

 been shown by Volta, that an entire frog may be convulsed by a degree of 

 electricity which affects an electrometer but very weakly; but that when 

 prepared in Galvani's manner, it will be agitated by an electricity one fiftieth 

 part as great, which cannot be discovered, by any other means, without the 

 assistance of a condenser. Galvani, however, found that a communication 

 made between the armed nerve and its muscle, by means of any conducting 

 substance, was sufiScient to produce a convulsion, without the presence of 

 foreign 'electricity: hence he concluded that the nerve and muscle, like the 

 opposite surfaces of a charged jar, were in contrary states of electricity, and 

 that the communication produced a discharge between them. He observed, 

 however, a considerable difference in the effects, when different metals were 

 employed far forming the circuit; and this circumstance led to the discovery 

 of the excitation of electricity by means of a combination of different inani- 

 mate substances only, which Mr. Davy attributes to Fabroni, Creve, and Dr. 

 Ash. It was, however, stilt more satisfactorily demonstrated by Volta; 

 and he at first supposed that all the phenomeaa observed by Galvani were de- 

 rived from effects of this kind, but on further examination he was obliged to 

 allow the independent existence of animal electricity. This industrious and 

 ingenious philosopher has the sole merit of the invention of the pile or battery, 

 which has rendered every other mode of exciting the galvanic action compa- 

 ratively insignificant. 



No sooner was VoUa's essay communicated to the Royal Society, than a 



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