[A] Bibliotheque Universelle, xxxvii. 15.

350.  Only those effects are weak or deficient which depend upon a certain high degree of intensity; and if common electricity be reduced in that quality to a similar degree with the thermo-electricity, it can produce no effects beyond the latter.

* * * * *

V. Animal Electricity.

351.  After an examination of the experiments of Walsh[A] Ingenhousz[B], Cavendish[C], Sir H. Davy[D], and Dr. Davy[E], no doubt remains on my mind as to the identity of the electricity of the torpedo with common and voltaic electricity; and I presume that so little will remain on the minds of others as to justify my refraining from entering at length into the philosophical proofs of that identity.  The doubts raised by Sir H. Davy have been removed by his brother Dr. Davy; the results of the latter being the reverse of those of the former.  At present the sum of evidence is as follows:—­

  [A] Philosophical Transactions, 1773, p. 461.

  [B] Ibid. 1775, p. 1.

  [C] Ibid. 1776, p. 196.

  [D] Ibid. 1829, p. 15.

  [E] Ibid. 1832, p. 259.

352. Tension.—­No sensible attractions or repulsions due to tension have been observed.

353. In motion:  i.  Evolution of Heat; not yet observed; I have little or no doubt that Harris’s electrometer would show it (287. 359.).

354. ii. Magnetism.—­Perfectly distinct.  According to Dr. Davy[A], the current deflected the needle and made magnets under the same law, as to direction, which governs currents of ordinary and voltaic electricity.

  [A] Philosophical Transactions, 1832, p. 260.

355. iii. Chemical decomposition.—­Also distinct; and though Dr. Davy used an apparatus of similar construction with that of Dr. Wollaston (327.), still no error in the present case is involved, for the decompositions were polar, and in their nature truly electro-chemical.  By the direction of the magnet it was found that the under surface of the fish was negative, and the upper positive; and in the chemical decompositions, silver and lead were precipitated on the wire connected with the under surface, and not on the other; and when these wires were either steel or silver, in solution of common salt, gas (hydrogen?) rose from the negative wire, but none from the positive.

356.  Another reason for the decomposition being electrochemical 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, unless the electricity had risen 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 conductor by sulphate of soda, common salt, or other saline bodies.  But in Dr. Davy’s experiments with the torpedo, strong solutions of salt, nitrate of silver, and superacetate of lead were used successfully, and there is no doubt with more success than weaker ones.