Transmission of the shock 207 



429] Whenever the electricity passed through the chain, a small light 

 was visible, provided the room was quite dark. This, however, affords 

 no argument for supposing that the phenomena of the torpedo are not 

 owing to electricity; for its shock has never been known to pass through 

 a chain or any other interruption in the circuit; and consequently, it is 

 impossible that any light should have been seen. 



430] In all these experiments, the battery was charged to the same 

 degree; namely, such that the shock was nearly of the same strength as 

 that of the leathern torpedo, and which I am inclined to think, from my 

 conversation with Mr Walsh, may be considered as about the medium 

 strength of those of a real one of the same size as this. It was nearly 

 equal to that of the plate of crown glass in Art. 411, electrified to such 

 a degree as to discharge itself when the knobs of a Lane's electrometer 

 were at ,0115 inches distance; whence a person, used to electrical experi- 

 ments, may ascertain its strength*. The way I tried it was by holding 

 the Lane's electrometer in one hand, with the end resting on the upper 

 surface of the plate, and touching the lower surface with the other hand, 

 while an assistant charged the plate by its upper side till it discharged 

 itself through the electrometer and my body. There is, however, a very 

 sensible difference between the sensation excited by a small jar or plate 

 of glass like this, and by a large battery electrified so weakly that the 

 shock shall be of the same strength; the former being sharper and more 

 disagreeable. Mr Walsh took notice of this difference; and said, that the 

 artificial torpedo produced just the same sensation as the real one. 



431] As it appeared, that a shock of this strength would pass through 

 a few intervals of the links of the chain, I tried what a smaller would do. 

 If the battery was charged only to a fourth or fifth part of its usual height, 

 the shock would not pass through a single interval ; but then it was very 

 weak, even when received through a piece of brass wire, without any link 

 in it. This chain was quite clean and very little tarnished; the lowest link 

 was larger than the rest, and weighed about eight grains. If I used a 

 chain of the same kind, the wire of which, though pretty clean, was grown 

 brown by being exposed to the air, the shock would not pass through a 

 single interval, with the battery charged to about one-third or one-half 

 its usual strength. 



432] It appears, that in this respect the artificial torpedo does not 

 completely imitate the effects of the real one, though it approaches near 

 to it; for the shock of the former, when not stronger than that of the 

 latter frequently is, will pass through four or five intervals of the links of 

 a chain; whereas the real torpedo was never known to force his through 

 a single interval. But, I think, this by no means shews, that the phenomena 



* [Charge of plate = 4100 inches of electricity = 5207 centimetres capacity. 

 Electromotive force = 5-5. See Note 10.] 



