VOL. LXVI.] PHILOSOPHICAL TKANSACTIONS. TJ 



to be electrified in such a degree that the shock shall be of a given strength. 

 It must be observed, that in the last mentioned experiment, the quantity of 

 electric fluid which passed through my body, was twice as great in taking the 

 shock of the 4 jars, as in taking that of the single one ; but the force with 

 which it was impelled was evidently less, and I think we may conclude, was 

 only half as great. If so, it appears that a given quantity of electricity, impel- 

 led through our body with a given force, produces a rather less shock than twice 

 that quantity, impelled with half that force ; and consequently, the strength of 

 the shock depends rather more on the quantity of fluid which passes through our 

 body, than on the force with which it is impelled. 



That no one could ever perceive the shock to be accompanied with any attrac- 

 tion or repulsion, does not seem extraordinary ; for as the electricity of the tor- 

 pedo is dissipated by escaping through or over the surface of its body, the in- 

 stant it is produced, a pair of pith balls suspended from any thing in contact 

 with the animal, will not have time to separate, nor will a fine thread hung near 

 its body have time to move towards it, before the electricity is dissipated. Accord- 

 ingly I have been informed by Dr. Priestley, that in discharging a battery, he 

 never could find a pair of pith balls suspended from the discharging rod to sepa- 

 rate. But besides, there are scarcely any pith balls so fine, as to separate when 

 suspended from a battery so weakly electrified, that its shock will not pass 

 through a chain, as is the case with that of the torpedo. 



In order to examine more accurately, how far the phenomena of the torpedo 

 would agree with electricity, I endeavoured to imitate them by means of a par- 

 ticular apparatus, made of wood, to represent a torpedo, connected with glass 

 tubes and wires, and covered with a piece of sheep's-skin leather. In making 

 experiments with this instrument, or artificial torpedo as I shall call it, after 

 having kept it in water of about the same saltness as that of the sea, till 

 thoroughly soaked, I fastened the end of one of the wires to the negative side 

 of a large battery, and when it was sufficiently charged, touched the positive side 

 with the end of the wire ; by whicii means the battery was discharged through 

 the torpedo. 



The battery was composed of 49 jars, of extremely thin glass, disposed in 7 

 rows, and so contrived that I could use any number of rows I chose. The out- 

 sides of the jars were coated with tin foil; but as it would have been very diffi- 

 cult to have coated the insides in that manner, they were filled with salt water. 

 In a battery to answer the purpose for which this was intended, it is evidently 

 necessary that the metals serving to make the communications between the 

 different jars should be joined quite close : accordingly care was taken that the 

 contacts should be made as perfect as possible. I find, by trial, that each row 

 of the battery contains about \b% times as much electricity, when both are 



