.,(' 'MCITY IX MOTION. 



It is unquestionable <h:it thi> torpedo, the gymnotus electrii 

 and .M>Hie other iislus, have organs appropriated to the excitation 

 of electricity, and that they have a power of communicating this 

 electririt\ at pleasure to conducting substances in their neighbour- 

 hood. These organs somewhat resemble in their appearance the 

 plates of the galvanic pile, although we know nothing of the im- 

 mediate arrangement from which their electrical properties are 

 derived ; l;ut the effect of the shock which they produce, resembles 

 in all respects that of the weak charge of a very large, bat. 

 tery. It has been shewn by the experiments of (Jalvani, Volta, 

 and Aldini, that the nerves and muscles of the human body possess 

 some electrical powers, although they are so much l*-ss concerned 

 in the phenomena which were at first attributed to them by Gal- 

 vani, than he originally supposed, that many philosophers have 

 been inclined to consider the excitation of electricity as always 

 occasioned by the inanimate substances employed, and the spas- 

 modic contractions of the muscles as merely very delicate tests of 

 the influence of foreign electricity on the nerves. 



Such is the general outline of the principal experiments and con- 

 clusions which the subject of galvanism afforded before Mr. Davy's 

 late ingenious and interesting researches, which have thrown much 

 light, not only on the foundation of the whole of this class of 

 phaenomena, but also on the nature of chemical actions and affinities 

 in general. Mr. Davy is inclined to infer from his experiments, 

 that all the attractions, which are the causes of chemical combina- 

 tions, depend on the opposite natural electricities of the bodies 

 concerned ; since such bodies are always found by delicate tests, 

 to exhibit, when in contact, marks of different species of elec- 

 tricity ; and their mutual actions may be either augmented or 

 destroyed, by increasing their mutual charges of electricity, or by 

 electrifying them in a contrary way. Thus an acid and a metal 

 are found to be negatively and positively electrical with respect to 

 each other ; and by further electrifying the acid negatively, and 

 the metal positively, their combination is accelerated ; but when 

 the acid is positively electrified, or the metal positively, they have 

 no effect whatever on each other. The acid is also attracted, 

 as a negative body, by another positively electrified, and the 

 metal by a body negatively electrified, so that a metallic salt may 

 be decomposed in the circuit of Volta, the positive point attract- 

 ing the acid, and the negative point the metal : and these attrac- 



