548 DR. DAVY ON THE TORPEDO. 



then irritated the fish with the contact wires in the usual manner, the galvanometer 

 attached to the contact wires has been distinctly affected. 



In my former paper I have stated my inability to account for my brother, the late 

 Sir Humphry Daw, not having obtained any positive results in his experiments on 

 the Torpedo. After reconsidering the subject, I am disposed to think it might have 

 been owing to his using large fish, without the means of ascertaining their electrical 

 activity, excepting by the shock. And we have seen, that when the human body 

 forms part of the circle of communication with a galvanometer, the latter is not affected 

 in the passage of the electricity producing the shock, which may serve to explain his 

 not having witnessed any effect on the instrument at Trieste. As regards the electri- 

 cal energies of large Torpedos, nothing is more uncertain. There appears to be no 

 relation between the muscular and electrical power. I have seen strong vivacious 

 fish, which made great muscular exertions in the water, almost or entirely destitute 

 of electrical power ; and, on the contrary, I have seen others languid and moribund, 

 which have exerted considerable electrical power. Small fish are almost always 

 active electrically, and they are greatly to be preferred as subjects for experiment. 

 Mr. Walsh noticed, in the fish on which he experimented at Rochelle and the Isle of 

 Re, a retraction of the eyes of the Torpedo at the instant it exercised its electrical 

 function. This I have not witnessed in the Torpedos of the Mediterranean ; nor, 

 indeed, have I been able to associate any visible sign, any apparent movement of the 

 fish, with the electrical discharge. 



The electricity of the Torpedo, theoretically considered, offers a wide field for 

 speculation. Is it, it may be asked, merely a form or variety of common electricity, 

 or a distinct kind, or not a single power, but a combination of many powers ? 



The first opinion, which is commonly received, and which has been ably advocated 

 recently by Mr. Faraday, is supported by the majority of the facts adduced in this 

 paper. The circumstance principally hostile to it, at least in appearance, is the inter- 

 ruption of the torpedinal electricity by the smallest quantity of air, and its want of 

 the power of attraction and repulsion in the air. 



These peculiarities are seemingly in favour of the second opinion, that the electri- 

 city of the Torpedo is specific and peculiar. But, till the opposite surfaces of the elec- 

 trical organs can be perfectly insulated, so that no easier mode of communication is 

 afforded than through air, they can hardly be considered as deserving of much 

 weight *. The origin of the electricity of this fish perhaps offers a stronger argument 

 in favour of its specific nature ; being, apparently, peculiar and distinct from any 

 known mode of electrical excitement, independent, as far as we can judge, of chemi- 

 cal action, or change of temperature, or change of form. But this argument may be 



* In the experiments in which I attempted to insulate the surfaces by means of oil, the probability is, that I 

 failed, and that a communication continued, if not by the outer surface of the skin, at least by its inner ; indeed, 

 the attempt to insulate these organs in the manner desired seems to be almost hopeless. 



