356 Mr. Faraday's Experimental Researches in Electricity. 



chemical is, that a Wollaston's apparatus constructed with 

 wires, coated by sealing-wax, would most probably not have 

 decomposed water, even in its own peculiar way, without the 

 electricity rising high enough in intensity to produce sparks 

 in some part of the circuit ; whereas the torpedo was not able 

 to produce sensible sparks. A third reason is, that the purer 

 the water in Wollaston's apparatus, the more abundant is the 

 decomposition : and I have found that a machine and wire 

 points which succeeded perfectly well with distilled water, 

 failed altogether when the water was rendered a good con- 

 ductor by sulphate of soda, common salt, or other saline bodies. 

 But in Dr. Davy's experiments with the torpedo, strong solu- 

 tions of salt, nitrate of silver, and superacetate of lead were 

 used successfully, and there is no doubt with more success 

 than weaker ones. 



357. iv. Physiological Effects. — These are so characteristic, 

 that by them the peculiar powers of the torpedo and gymnotus 

 are principally recognised. 



358. v. Spark. — The electric spark has not yet been ob- 

 tained, or at least I think not ; but perhaps I had better refer 

 to the evidence on this point. Humboldt, speaking of results 

 obtained by M. Fahlberg, of Sweden, says, " This philoso- 

 pher has seen an electric spark, as Walsh and Ingenhousz had 

 done before him at London, by placing the gymnotus in the 

 air, and interrupting the conducting chain by two gold leaves 

 pasted upon glass and a line distant from each other*." I 

 cannot, however, find any record of such an observation by 

 either Walsh or Ingenhousz, and do not know where to refer 

 to that by M. Fahlberg. M. Humboldt could not himself per- 

 ceive any luminous effect. 



Again, Sir John Leslie, in his dissertation on the progress 

 of mathematical and physical science, prefixed to the seventh 

 edition of the Encyclopedia Britannica, Edinb. 1830, p. 622, 

 says, " From a healthy specimen" of the Silurus electricus, 

 meaning rather the gymnotus, " exhibited in London, vivid 

 sparks were drawn in a darkened room ;" but he does not say 

 he saw them himself, nor state who did see them; nor can 

 I find any account of such a phenomenon ; so that the state- 

 ment is doubtful f. 



359. In concluding this summary of the powers of torpe- 

 dinal electricity, I cannot refrain from pointing out the enor- 

 mous absolute quantity of electricity which the animal must 



• Edinburgh Phil. Journal, ii. p. 249. 



f Mr. Brayley, who referred me to these statements, and has extensive 

 knowledge of recorded facts, is unacquainted with any further account re- 

 lating to them. 



