Benjamin Franklin Papers

To Benjamin Franklin from John Walsh, 12 July 1772

From John Walsh5

ALS: American Philosophical Society

La Rochelle 12th. July 1772.

Dear Sir

It is with particular Satisfaction I make to You my first Communication that the Effect of the Torpedo appears to be absolutely electrical, by forming it’s Circuit thro’ the same Conductors with Electricity, for instance Metals, Animals, and moist Substances; and by being intercepted by the same non-conductors, for instance Glass and Sealing Wax.6 I will not at present trouble You with a Detail of our Experiments, especially as we are dayly advancing in them, but only observe that having discover’d the Back and Breast of the Animal to be in different States of Electricity (I speak of that assemblage of pliant Cylinders described by Lorenzini, running perpendicularly from the Back to the Breast, and having some resemblance of the Cells of a Honeycomb7) we have been able to convey his Shocks tho’ they were very small, thro’ a Circuit of four Persons, all feeling it, and thro’ a considerable length of Wire held by two insulating Persons, one touching his lower Surface and the other his upper. The Wire exchanged for Glass or Sealing Wax, no effect could be produced. Resuming the Wire, and two Persons were again sensible of the Shock.8 These Experiments have been varied and repeated without Number, by which the Choice of Conductors is beyond a Doubt determined to be the same in the Torpedo and the Leyden Phial. The Sensation they occasion likewise in the Human Frame is precisely similar: there is not an Engourdissement or Fourmillement of the Torpedo that we do not most exactly imitate with the Phial by means of Lane’s Electrometer.1 We have not yet perceived any Spark or Noise to accompany the Shock, nor that Canton’s Balls were affected by it.2 Indeed all our Tryals have been on very feeble Subjects; whose Shock extended seldom further than the touching finger; I remember it, but once, in above two hundred that I must have taken, to have extended above the Elbow. Perhaps L’Isle de Ré, which we are about to visit, may furnish us with Torpedos fresher taken and of more Vigour,3 that may give us further insight into these Matters. Our Experiments have been cheifly in the Air, where the Animal was more open to our examination than in Water. It is a Singularity that the Torpedo when insulated should be able to give us, insulated likewise, thirty forty or fifty Shocks from nearly the same part, and this with very little Diminution in their Stre[ngth;?]4 indeed they were all minute. Each Shock is conveniently accompanied by a depression of his Eyes, by which we were ascertained of his Attempt to give it to non-conductors. The Animal with respect to the Rest of his Body is in great degree motionless, but not wholly so. You will please to acquaint Dr. Bancroft of our having thus verified his Prediction concerning the Torpedo5 and make any other Communication of this Matter you may judge proper. Here I shall be glad to excite the Electricians and Naturalists to push their Enquiries concerning this extraordinary animal, whilst the Summer affords them the opportunity. I am with the truest Sentiments of Esteem and Respect Dear Sir Your most obedient humble Servant

John Walsh

If you favour me with a Line you will please to direct to me at Sr. John Lamberts6 at Paris: who will forward it to me whether I may [be] here or at Bourdeaux.

Addressed: To Doctor Franklin / Craven Street / London.

Endorsed: Fm J Walsh

[Note numbering follows the Franklin Papers source.]

5This letter and parts of the one below of Aug. 27 were submitted to the Royal Society, as Walsh requested in his letter to BF of July 1, 1773, and published in Phil. Trans., LXIII (1773–74), 462–6. The printed text has changes in wording and substance, most of which are too minor to deserve notice.

6Substances that transmit but do not store electricity, such as metals, were originally called non-electrics, whereas those that store but do not transmit it, such as glass and wax, were called electrics; BF renamed them conductors and non-conductors. See above, IV, 203–4, 297–8; IX, 350 n.

7The electric organs of the torpedo, consisting of metamorphosed muscular tissue, are columns of discs or electrical plates, each of which is charged positively on its upper surface and negatively on its lower.

8Walsh’s second report, Aug. 27, gives further details.

1This sentence was rewritten when the letter was published: “Not only the shock, but the numbing sensation which the animal sometimes dispenses, expressed in French by the words engourdissement and fourmillement, may be exactly imitated with the Phial, by means of Lane’s Electrometer; the regulating rod of which, to produce the latter effect, must be brought almost into contact with the prime conductor which joins the Phial.” Phil. Trans., LXIII (1773–74), 463. For the electrometer, which permitted varying the discharges from a Leyden jar, see above, XIII, 459–65.

2Walsh explains the absence of these effects in his second report.

3Rhé, once known in England as the “Isle of Rue” because of a disaster there to English arms in 1627, lies off La Rochelle; limestone reefs north of the island were presumably, at low tide, Walsh’s hunting ground for torpedoes.

4The MS is torn; the printed version reads “Force.” Walsh was puzzled, we assume, because he was thinking in terms of analogy with the Leyden jar, in which the charge was reduced or dissipated, whereas the fish could discharge indefinitely.

5That its shocks were electrical; see above, p. 161.

6See Walsh’s letter of June 21 above.

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