TOL. LXIII."] PHILOSOPHICAL TRANSACTIOKS. 473 



when he was disposed to give it, than it would prevent the shock of the Leyden 

 Phial. 



Several persons, forming as many distinct circuits, can be afFecled by one 

 stroke of the animal, as well as when joined in a single circuit. For instance, 

 4 persons, touching separately his upper and lower surfaces, were all affected; 

 1 persons likewise, after the electricity had passed through a wire into a basin 

 of water, transmitted it from thence, in 2 distinct channels, as their sensation 

 convinced them, into another basin of water, whence it was conducted, probably 

 in a united state, by a single wire. How much further the effect might be thus 

 divided and subdivided into different channels, was not determined; but it was 

 found to be proportionably weakened by multiplying these circuits, as it had 

 been by extending the single circuit. 



Something may be expected to be said of the parts of the animal immediately 

 concerned in producing the electrical effect. The engraving, which accompanies 

 this letter, while it shows the general figure of the torpedo, gives an internal 

 view of his electric organs. The society will, besides, have a full anatomical 

 description of these parts from the ingenious Mr. John Hunter, in a paper he 

 has expressly written on the subject at my request. It would therefore be super- 

 fluous for me to say any thing either in regard to their situation or structure. 



I have to observe however, that in these double organs resides the electricity 

 of the torpedo; the rest of his body appearing to be no otherwise concerned in 

 his electrical effect, than as conducting it: that they are subject to the will of 

 the animal; but whether, like other double parts so controlable, they are exer- 

 cised, at times, singly as well as in concert, is difficult to be ascertained by 

 experiment: that their upper and under surfaces are capable, from a state of 

 equilibrium with respect to electricity, of being instantly thrown, by a mere 

 energy, into an opposition of a plus and minus state, like that of the charged 

 phial: that when they are thus charged, the upper surfaces of the two are in 

 the same state of electricity; as are the under surfaces of the two, though in a 

 contrary to that of the upper; for no shock can be obtained by an insulated 

 person touching both organs above, or both below: and that the production of 

 the eflFects depends solely on an intercourse being made between the opposite 

 surfaces of the organs, whether taken singly or jointly. 



All the parts bordering on the organs act, more or less, as conductors, either 

 through their substance or by their superficies. While an insulated person, 

 placing 1 fingers on the same surface of one or both organs, cannot be affected; 

 if he removes one of his fingers to any such contiguous part, he will be liable 

 to a shock : but this shock will not be near, perhaps not half, so violent, as one 

 taken immediately between the opposite surfaces of the organ; wliich shows tlie 



3p2 



