XXXIX. Of the electric property of the torpedo. In a letter from John Walsh, Esq; F. R. S. to Benjamin Franklin, Esq; LL. D., F. R. S., Ac. R. Par. Soc. Ext., &c. [ 46* ] XXXIX. O f the eleSlr Property of the "Torpedo. In a Letter from John Walfh, Efq\ F. R. S. to Benjamin Franklin, Ffq\ L L . D., F, R. Ac. R. Par. Soc. Ext., 8cc. Chefterfield-Street, July x, 175*3. D e a r S i r , R.<:ad July 1, y Am concerned that other engagements 1 have prevented me from giving to the Royal Society, before their recefs, a complete ac­ count of my experiments on the eledtricity of the Torpedo; a fubjedt not only curious in itfelf, but opening a large field for interefiing inquiry, both to the eledfrician in his walk of phyfics, and to all who confider, particularly or generally, the animal ceconomy. T o fupply the deficiency in the befi: manner I am now able, I will requeft the favour of you to lay be­ fore the Society my letter from la Rochelle, of the 12th July 1772, and fuch part of the letter I after­ wards wrote from Paris, as relates to this fubjedh Loofe and imperfedt as thefe informations are, for they were never intended for the public eye, they are ftill the moft authentic, and fo far the moll O 0 0 2 fatif- D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 fatisfadory I can at prefent offer, fince the notes I made of the experiments themfelves remain nearly, I am forry to fay it, in that crude and bulky ftaic in which you had the trouble to read them. letter from Mr. W alsh to Dr. F ranklin, dated la Rochelle, 12th July 1772. uIt is with particular fatisfadion I make to you “ my firft communication, that the effed of the “ Torpedo appears to be abfolutely eledrical; by " forming its circuit through the fame condudors “ with eledricity, for inftance metals, and water ; “ ar?d by being intercepted by the fame non-con- c< dudors, for inftance glafs, and fealing-wax. I “ will not at prefent trouble you with the detail o f “ our experiments, efpecially as we are daily ad- “ vancing in them ; but only obferve, that we have difcovered the back and breaft of the animal to be u in different ftates of eledricity: I mean in par- cc ticular the upper and lower furfaces of thofe two * affemblages of pliant cylinders, of which you a have feen engravings in Lorenzini *. By the v knowledge of this circtimftance we have been “ able to dired his (hocks, though they were very ? fmall, through a circuit of four perfons, all feel- cc ing th em ; likewife through a confiderable length “ °J wire held by two infulated perfons, one touching u his lower fur face, and the other his upper. W hen O bfervazioni intorno alle Forpedini di Stef. L o r e n z in i 6 7 8*. ^ Redi appears to be the lirft who remarked thefe fingular parts «<£ the T orp ed o in 1 6 6 6 . F ranc. R ed i, E xper, N a t. t .6* ] “ the D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 4 ^ 3 ] the wire was exchanged for glafs, or healing-wax, no effeft could be obtained: but as foon as it wag refumed, the two perfons became liable to the fhock. Thefe experiments have been varied many ways, and repeated times without number, and they all determined the choice pf condudors to be the fame in the Torpedo as in the Ley- den Phial. T h e fenlations like wife, occafioned by the one and the other in the human frame, are precifely fiinilar. N ot only the (hock, hut the numbing fenfation which the animal fome times difpenfes, exprefifed in French by the words v i­ gour diffement and Jourmillement, may be exadly imi­ tated with the Phial, by means of Lane’s Elcdro- m etei; the regulating rod of which, to produce the latter efFed,, muft be brought almoA into contad with the prime condudor which joins the Phial. W e have not yet perceived any fpark to accompany the fhock, nor the pith balls to be ever affeded. Indeed ail our trials have been on very feeble fubjeds, whole fhock was feldom fenfible beyond the touching finger: I remember but one, of at leaft two hundred, that I myfelf rnufi have re­ ceived, to have extended above the elbow. Per­ haps the Hie of Re, which we are about to vifit, may furnifb us with Torpedos frefher taken and of more vigour, by which a farther infight into thefe m atter may be had. Our experiments have been chiefly jn the air, where the animal was more open to our examination than in water. It is a Angularity that the Torpedo, when inhibited, liquid be able to give to us, infulated hkewife, forty or fifty fuccefiive fhocks from n e a r l y the D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 fame part; and thefe with little, if any diminu- tiv)fi in their force i indeed they were all very minute. Each cixort in the animal to give the fhock lV conveniently accompanied with a de* “ P^ffion of his eyes, by which even his attempts 772 As it came from a very relpedtable quarter, not lefs fo from the private character of the gentleman, than from the public offices he held, I mud dehie leave of the Society to avail myielf of fuch a tedimony to the fads 1 have advanced, by giving a trandation of that narrative. E xtrad of a Letter from the Sieup Se i g n e t t e , Mayor of la Rochelle, and fecond perpetual Secretary of the Academy of that City, to the publifher of the French Gazette. 4< In the Gazette of the 14th Augud, you men- tinned the difeovery made by Mr. Walfh, Mem- “ her D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 . f m I berof th ep arliam e n t p f England, £nd of tlie “ Royal Society p f London* T h e experiment, o f “ which I am going to give you an account, was “ made in the prefence o f the Academy o f this “ city. A live Torpedo was placed on a table. “ Round another table flood five perfons infulated* tc T w o brafs wires, each thirteen feet long, were “ fufpended tp the ceiling by filken firings. One “ o f thefe wires refted by one end on the w et “ napkin on which the fifh lay ; the other end 64 was immerfed in a bafin full of water plated “ on the fecond table, on which flood four other u bafins likewife full o f water. T h e firft perfon “ put a finger o f one hand in the bafin in which «>. the wire was immerfed, and a finger o f the « other hand in the fecond bafin. T h e fecond “ perfon put a finger of one hand in this laft “ bafin, and a finger of the other hand in the « t h i r d ; and fo on fucceflively, till the five per- « fbn§ communicated w ith one another by the “ water in the bafins. In the laft bafin one end « of the fecond wire was immerfed ; and w ith v the other end M r. W alfh touched the back o f «« the Torpedo, when the five perfons felt a com- « motion which differed in nothing from that o f M the Leyden experiment, except in the degree o f “ fprce. M r. W alfh, who was not in the circle it of condu&ion, received no fhock. T h is expe- m rim ent was repeated feveral times, eveu w ith eight perfons; and always with the fame fuc- cefs. T h e action o f the Torpedo is commu- nicated by the fame mediums as that o f the « e,le6tric fluid. T h e bodies which intercept the V p t . L X III. P p p “ adion D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 4 ^ 8 ] 4< adion o f the one, intercept like wife the adion w o f the other. T h e effects produced by the “ Torpedo referable in every refped a w eakelec- “ tricity.” T his exhibition o f the eledric powers o f the Torpedo, before the Academy of L a Rochelle, was at a meeting, held for the purpofe in my apartments, on the 22d July 1772, and Rands regiftered in the journals of the Academy. T h e effed of the animal was, in thefe. experi­ ments, tranfmitted through as great an extent and variety of condudors as almoR at any time we had been able to obtain it, and the experiments in­ cluded, nearly, all the points, in which its analogy w ith the effed o f the Leyden Phial had been obferved. Thefe points were Rated to the gentle­ men prefent, as were the circumRances in which the two effeds appeared to vary. It was likewife reprefented to them, T h at our experiments had been almoR wholly w ith the animal in a ir: T h at its adion in water was a capital defideratum: T h a t indeed all as yet done was little more than opening the door to in q u iry : T h a t much remained to be examined by the Eledrician as well as by the AnatomiR : T h a t as artificial eledricity had thrown light on the natural operation o f the Torpedo, this might in return, if well confidered, throw light on artificial eledricity, particularly in thofe refpeds in which they now feemed to differ: T h a t for me, I was about to take leave o f the animal, as nature had denied it to the Britifh feas 1 and that the profecution of thefe refearches D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 retted in a particular manner w ith them , whofe ftiores abounded w ith it. T h e Torpedo, on this occafion, difpenfed only the diftindt, inftantaneous ftroke, fo well known by the name of the ele&ric fhock. T h a t pro- trafted but lighter fenfation, that Torpor or Numbnefs which he at times induces, and from w hich he takes his name, was not then experi­ enced from the an im al; but it was imitated with artificial electricity, and jfhewn to be producible by a quick confecution o f minute (hocks. T his, in the Torpedo, may perhaps be effected by the fuc- ceffive difcharge of his numerous cylinders, in the nature o f a running fire of m u lk etry : the ftrong fingle fliock may be his general volley. In the continued effedt, as well as in the inftantaneous, his eyes, ulually prominent, are withdrawn into their fockets. T h e fame experiments, performed w ith the fame Torpedos, were on the two fucceeding days repeated before numerous companies of the prin­ cipal inhabitants o f L a Rochelle. Befides the pleafure o f gratifying the curiofity o f fuch as en ­ tertained any on the fubjedt, and the defire I had to excite a profecution of the inquiry, I certainly wifhed to give all poflible notoriety to fadls, which m ight otherwife be deemed improbable, perhaps by fome of the firft rank in fcience. Great au­ thorities had given a fan&ion to other folutions o f the phoenomena of the Torpedo ; and even the Eledhician m ight not readily liften to afiertions, w hich feemed, in fome' refpedb, to combat the es of electricity, I had reafon to P p p 2 make [ 469 ] general principl D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 make fuch conclufions from different converfations I had held on the fubjeft w ith eminent perform both at London and Paris. It is but juftice to fay, that of all in that clafs you gave me the greateft encouragement to look for fuccefs in this refearch, fuid even affifted me in forming hypothefes, hoW the Torpedo, fuppofed to be endued w ith electric .properties, m ight ufe them in fo conducing an element as water. After generally recommending to others an ex­ amination o f the ele&ric powers o f thefe animals when acting in water, I determined, before I took m y final leave o f them , to make fome farther ex­ periments myfelf w ith that particular view ; fince, notwithftanding the familiarity in which we may t e faid to have lived w ith them for near a m onth, we had never detedted them in the immediate exer- cife of their eledtric faculties againft other filh, confined w ith them in the fame water, either in the circumftance of attacking their prey, or de­ fending themfelves from annoyance: and yet that they poffeffed fuch a power, and exercifed it in. a ftate of liberty, could not be doubted. A large Torpedo, very liberal o f his fhocks, being held w ith both hands by his eledtric organs above and below, was brifkly plunged into water to the depth of a foot, and inftantly raifed an equal height into air •, and was thus continually plunged and raifed, as quick as poffible, for the fpace of a minute. In the inftant his lower fur- face touched the water in his defcent, he always gave a violent {hock, and another {till more vio­ lent in the inftant of quitting the water in his afcent; D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 a fe e n t; both which (hocks, but particularly the laft, were accompanied w ith a w rithing in h it body, as if meant to force an efcape : Befidet thefe two (hocks from the furface o f the water, w hich may yet be confidered as delivered in the air, he conftantly gave at lead two, when w holly in the air, and conftantly one and fometimes two, when w holly in the water. T h e (hocks in water appeared, as far as fenfation could decide, not to have near a fourth of the force o f thofe at the furface o f the water, nor much more than a fourth o f thofe inti rely in air. T h e (hocks received in a certain time were n o t,' On this occafion, counted by a watch, as they had been on a former, when fifty were delivered, in a minute and a half, by the animal in an in­ itia te d and unagitated date : But from the quick- nefs, w ith which the immerfions were made, it may be prefumed there were full twenty o f thefe' in a minute ; from whence the number o f (hocks, in that time, mu ft have amounted to above an hundred. T his experiment, therefore, while it difcovered the comparative force between a (hock in water and one in air, and between a (hock delivered w ith greater exertion on the part o f the animal and one with left, feemed to de­ termine, that the charge of his organs with elec­ tricity was effected in an inftant, as well as the difcharge. T h e Torpedo was then put into a flat bafleet, open at top, but fecured by a net with wide mefties, and, in this confinement, was let down' into the water, about a foot below the liirface; being [ 471 ] D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 E 4 7 2 ] being there touched, through the mefhes, w ith only a Angle fin g e r,o n one o f his ele&ric organs, w hile the other hand was held, at a dittance, in the water, he gave fhocks, which were diftin&Iv felt in both hands. , T h e circuit for the palfage of the effed being eon traded to the finger and thum b o f one hand, applied above and below to a fingle organ, produced a fhock, to our fenfation, of twice »tlie force of that in the larger circuit by the arms. T he Torpedo, ftill confined in the bafket, being raifed to within three inches of the furface o f the water, was there touched w ith a fliort iron bolt, which was held, half above and half in the w ater, by one hand, while the other hand was dipped, as before, at a dittance in the w ater; and flrong fhocks, felt in both hands, were thus ob­ tained through the iron. A wet hempen cord being fattened to the iron bolt, was held in the hand above water, while the bolt touched the Torpedo ; and Clocks were obtained through both thofe fubftances. A lefs powerful Torpedo, fufpended in a fmall net, being frequently dipped into water and raifed again, gave, from the furface o f the water, llight fhocks through the net to the perfon hold­ in g it. Thefe experiments in water manifefted, T h a t bodies, immerfed in that element, m ight be affec­ ted by immediate contad w ith the T orpedo; T h a t the ihorter the circuit in which the elec­ tricity D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 C 473 3 frk ity moved, the greater would be the effect;, And th a t the (hock was communicable, from th e animal in water, to perfons in air, through fome fubdances. How far harpoons and nets, confiding of wood and hem p, could, in like circumdances, as it has been frequently afferted, convey the effed, was, not fo particularly tried as to enable us to confirm, it. I mention the omiffion in the hope that fome one may be induced to determine the point by exp refs trial- W e convinced ourfelves,. on former occafions,{ th at the accurate Kaempfer *, who fo well de* fcribes the effed: of the Torpedo,, and happily compares it w ith lightning, was deceived in th e circumdance* that i t could, be avoided by holding, in the breath, which, we found no more to pre­ vent the (hock o f the Torpedo, when he was- difpofed to give it, than it would prevent the. (hock o f the Leyden Phial. Several perfons,. forming; as, many d id in d circuits, can be affeded by one droke o f the animal, as welL as when joined in a fingle circuit. F or in dance* four perfons, touching feparately his upper and lower fur faces,, were all affed ed ; two perfons like wile, after the eledricity had pafled through a wire into a bafin of water, tran f- m itted it from thence, i a two d id in d channels*, as their fenfation convinced them,., into another bafin of water, from whence, it was concluded* probably in an united date, by a>fingle wire.. How: * Kasmpf. Amcen. Exot. 1712, p. 5 14. mu cL D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 on the organ o f the other, was fenfible o f {hocks, fometimes delivered by one fifli, and fome- times by the other, as m ight be difcovered by the refpeCtive winking o f their eyes. T h a t the organs, uncharged, ferved fome way or other as conductors, was confirmed w ith artificial electricity, in paffing {hocks by th e m ; and in taking fparks from them , when electrified. T he deCtric eifeCt was never perceived by us t a be attended w ith any motion or alteration in the organs themfelves, but was frequently accom­ panied with a little tranfient agitation along the cartilages which furround both organs: this is not difcernible in the plump and turgid hate of the animal, while he is frefh and vigorous; but as his force decays, from the relaxation of his mufcles, his cartilages appear through the ikin, and then, the flight aCtion along them is difcovered. M ay we not from all thefe premifes conclude, that the effeCt o f the Torpedo proceeds from a modification o f the eleCtric fluid ? T h e T o r­ pedo refembles the charged Phial in that cha- raCteriftic point of a reciprocation between its two furfaces. T h eir effeCts are tranfmitted by. the fame m edium s; than which there is not per­ haps a furer criterion to determine the identity o f fubtile matter : T h ey , befides, occafion the fame impreflion on our nerves.. Like effeCts have like eaufes. But it may be objected, that the effeCts of the Torpedo, and o f the charged Phial, are not fimilar in all their circum ftances; that the charged. Phial occafions attractive or repulfive difpofitions [ 474 ] D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 in neighbouring bodies; and that its difcharge is obtained through a portion o f air, and is ac­ companied w ith light and found; nothing of w hich occurs w ith refpedl to the Torpedo, T h e inaction o f the eledlricity o f the animal in thefe particulars, whilft its elaftic force is fo great as to tranfmit the effedt through an extenfive cir­ cuit and in its courfe to communicate a fhock, may be a new phenom enon, but is no ways repug­ nant to the laws of eledlricity; for here too, the operations o f the animal may be imitated by art. T h e fame quantity of eledric m atter, according as it is ufed in a denfe or rare hate, will produce the different confequences. For example, a fmall P hial, whofe coated furface meafures only fix fquare inches, w ill, on being highly charged, contain a denfe eledlricity capable of forcing a paffage through an inch o f air, and afford the phenom ena o f light, found; attradlion, and re- pulfion. But i f the quantity condenfed in this Phial, be made rare by communicating it to three large connedled jars, whofe coated furfaces fhall form together an area 400 times larger than that o f the Phial (I inflance thefe jars becaufe they are fuch as I u fe ); it will, thus dilated, yield all the negative phenom ena, if I may fo call them , o f the Torpedo; it will not now pafs the hun­ dredth part of that inch o f air, which in its con­ denfed hate it fprung through w ith eafe; it will now refufe the minute interfedlion in the ftrip o f tin fo il; the fpark and its attendant found, even the attradlion or repulfion o f light bodies, will now Q q q ^ be [ 475 ] D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 1 4 7 6 ] he w an tin g ; nor will a point brought however near, if not in contact, be able to draw off the charge: and yet, with this diminiflied elafcicity, the eledtric matter will, to effedt its equilibrium, inftantly run through a confiderable circuit of dif­ ferent condudlors, perfedtly continuous, and make us' fenfible of an impulfe in its paffege. L e t me here remark, that the fagacity o f Mr*. Cavendifh in deviling and his addrefs in exe­ cuting ele&rical experiments, led him the firft to experience w ith artificial ele&ricity, that a fhock could be received from a charge which was unable to force a paffage through the leaf!: fpace of air. But, after the difcovery that a large area of rare eledlricity would imitate the effedt of the Torpedo, it may be inquired, where is this large area to be found in the animal? W e here approach to that veil o f nature, which man cannot remove. T his, however, we know, that from infinite divifion o f parts infinite furface may arife, and even our grofs optics tell us, that thofe lingular organs, fo often; mentioned, confift like our eledtric batteries o f many veflels, call them cylinders or hexagonal prifms, whofe fuperficies taken together furnifh a confiderable area. I rejoice in addreffing thefe communications to* You. He, who predided and fhewed that elec­ tricity wings the formidable bolt of the atm of- phere, will hear with attention, th at in the deep it fpeeds an humbler bolt, filent and invifible : He, who analyfed the eledtrified Phial, will hear w ith 2 pleafure D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 [ 477 ] pleafure that Its laws prevail in animate Phials t H e, w ho by Reafon became an ele&rician, will hear w ith reverence o f an infiin&ive ete&rician* gifted in his birth w ith a wonderful apparatus* and w ith the Ikill to ufe it. ^However I may refpeft your talents as an elec­ trician, it is certainly for knowledge of more ge­ neral im port, that I am impreffed with that h ig h efteem, w ith which I remain* Dear Sir, Your affe&ionate and obedient fervant* John Walllu E X - D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 EXPLANATION of the PLATE OF T H E Male and Female Torpedo, or Ele&ric Ray. T A B . X IX . F I G . I. A view of the under furface of the female. a. An expofure, on flaying off the Ik in, o f the right electric organ, which confifts o f white pliant columns, in a clofe and for the moft part hexagonal arrange­ ment, giving the general appearance o f a honey-comb in miniature. Thefe columns have been fometimes denomi­ nated cylinders; but, having no inter- ftices, they are all angular, and chiefly flx-cornered. b. T h e fkin which covered the organ, fhewing on its inward fide an hexa­ gonal net work. c. T he noftrils in the form of a crefcent. T he mouth in a crefcent contrary to that o f the noftrils, furniihed with feveral rows of very fmall hooked teeth. [ 478 ] e. T h e D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 e. T he branchial apertures, five on each fide. / T h e place o f the heart. £*£• S ' p l a c e o f the two anterior tranfverfe cartilages, which, paffing one above and the other below the fpine, fupport the diaphragm, and uniting towards their extremities, form on either fide a kind o f clavicle and fcapula. h, h.The outward margin o f the great lateral fin. /. / . Its inner margin, confining w ith the ele&ric organ. L T h e articulation of the great lateral fin w ith the fcapula. /. T h e abdomen. m. m.m. T h e place o f the pofterior tranfverfe car­ tilage which is fingle, united w ith the fpine, and fupports on each fide the Imaller lateral fins. [ 479 ] T h e anus. pr T h e fin o f the tail.m. F I G. D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 F I G. II. A view o f the upper furface o f the female. a. a. An expofure of the upper part of the right ele&ric organ. b. T h e Ikin which covered the organ. ?c.The eyes, prominent and looking hori­ zontally outwards, but capable of being occafionally withdrawn into their fockets. & T w o circular apertures communicating w ith the m outh, and furniflied each w ith a membrane, which in air, as well as in water, plays regularly backwards and forwards acrofs the aperture in the office o f infpiration, e. T h e place o f the right branchia, f . T he two fins o f the back. g. g. T h e place of the anterior tranfverfe car­ tilages. F I G. HI. A view o f the under furface o f the male, whofe fize, as here reprefented, is, in general, fmaller than that of the female. & a* T w o appendices, diftinguiftiing the male fpecies. [ 4«° ] XL. A D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1 D ow nl oa de d fr om h tt ps :/ /r oy al so ci et yp ub li sh in g. or g/ o n 05 A pr il 2 02 1