TORPEDO. 



the laft bafon one end of the fecond wire was dipped, and 

 with the other end Mr.Walfli touclied the back of the tor- 

 pedo, when the five perfons felt a fhock, differing in nothing 

 from that of the Leyden experiment, except in being weaker. 

 Mr. WaKh, who was not in the circuit, was not affefted. 

 This experiment was fuccefsfuUy repeated feveral times, 

 even with eight perfons. From this experiment it is evi- 

 dent, that the aftion of the torpedo is communicated through 

 metals and water, or, in general, through the fame media 

 that tranfmit the eleftrical concufTion. It follows, likewife, 

 that the upper and under parts of the animal, like the upper 

 and under furfaces of an eleftrified plate of glafs, are in dif- 

 ferent ftates ; for a perfon who touches only the upper or 

 the under furface of the eleSric organs, will not receive 

 the fliock of the torpedo. This aftion evidently depends 

 on the will of the animal, who, however, fcarcely exhibits 

 any other fenfible motion or effort at the time of exerting 

 it than a depreflion or winking of his eyes. The fame mo- 

 tion is obferved likewife to accompany its fruitlefs attempts 

 to tranfmit a fhock through non-conduftors. The ftock 

 of eleftrical matter which the torpedo poflefTes appears to 

 be. very confiderable : a torpedo, when infulated, has given 

 to Mr. Walfh, infulated likewife, no lefs than fifty fhocks 

 in the fpace of a minute and a half. 



Such are the operations performed by the toqjedo in air. 

 When a large fifh, very liberal of his fhocks, was held in 

 water, with one hand on his breaft and another on his back, 

 he gave the operator fhocks of the fame kind as before, but 

 about one-fourth of the ftrength of thofe given in air. At 

 the very inftant of raifing him out of the water, he con- 

 ftantly gave a very violent fhock, and another nearly as 

 violent, when his lower furface firfl touched the water on 

 dipping him into it. On brifkly and alternately plunging 

 him a foot deeper into water, and raifing him an equal 

 height into air, befides one or two fhocks which he gave 

 during the fhort time he was wholly in the water, and thofe 

 whicli he gave at the furface, he conflantly gave at Iraft 

 t«o when he was wholly in the air : fo that Mr. Walfh 

 eftimates that he gave above one hundred fliocks during the 

 minute in v.iiich the experiment was performed. The con- 

 clufions drawn from Mr. Walfh's experiments were farther 

 confirmed by fome experiments made on the torpedo at 

 Legliorn, by Dr. Ingenhoufz, in 1773- 



Mr. Walfh obferves, that the cleftricity of the torpedo 

 rcfides in thofe parts that are called his eleftric organs : 

 the parts bordering on thefe afting, more or lefs, as con- 

 duftors, either through their fubilancei or by their fuper- 

 ficies : and of thefe, the parts which conduft the befl are 

 the two great lateral fins bounding the organs outwardly, 

 and U'c fpace lying between the two organs inwardly. All 

 below the double tranverfe cartilages fcarcely conduft at all, 

 unlefs when the fifli is juft taken out of water and is ftill 

 wet, the mucus, with which he is lubricated, fhewing itfelf, 

 as it dries, to be of an infulating nature ; and the organs 

 themfelves, wlien uncharged, appeared to be, not interiorly 

 but rather exteriorly, as Mr. Walfli fuppofes, conduftors 

 of a fhock. We are indebted to Mr. John Hunter for an 

 accurate anatomical defcription of the torpedo, accompa- 

 nied with two excellent drawings, who has thus fupplied us 

 with a valuable addition to the anatomical examination of 

 this animal by Redi, Steno, and Lorenzini. For his account, 

 we refer to Ele&ric Organs of FiSH. 



Although Mr. Walfla's experiments leave little room to 

 doubt, tliat the fhock given by the torpedo is produced by 

 the fame agent that gives the fhock in an eleftrical explo- 

 fion, yet there are fome circumflances which it is difficult to 

 reconcile to the fuppofition that it is produced by the 



Vol. XXXVI, 



eleftric fluid. One of thefe difficulties is, that the fifh is 

 able to give a fhock when he is in the water, and confe- 

 quently furrounded by a medium, through which the 

 eleftric fluid is known to be tranfmitted with the greatefl 

 facihty. It has hkewife been difficult to conceive why the 

 fhock of the torpedo, fuppofing it to be produced by the 

 eleftric fluid, fhould not, like that of an eleftrified jar, be 

 accompanied with the appearance of hght or fparks, or 

 fhould not exhibit fome figns of attraftion or repulfion. 

 But from Mr. Walfh's experiments it appears, that no light 

 could poflibly accompany the fhock of the torpedo, becaule 

 this fhock could never be made to pafs through the leaff 

 fenfible fpace of air, or the Imallell interruption made by 

 the circuit ; not even through the imperceptible interval 

 between the links of a flender brafs chain, apparently in 

 contaft with each other, nor over an almoft imperceptible 

 interval or flit formed by cutting through a flip of tin-foil 

 palled on fealing-wax, which conflituted part of the circuit ; 

 nor are the mofl dehcate pith-balls, or other hght bodies, in 

 what manner foever applied, in the leaft degree affefted 

 at the time of the fliock. Mr. Walfh obferves, that, with 

 refpeft to the pith-balls, it is not furprifing that no motion 

 could be difcovered in them, as all his experiments fully 

 fliewed that there was no gradual accumulation of the 

 eleftric fluid, as in the cafe of charged glafs ; but that it 

 was collefted or condenfed in the very inftant of the explo-' 

 fion, by a fudden energy of the animal. He alfo explains 

 this and the other differences between the phenomena of the 

 Leyden phial, and of the torpedo, or the abfence. of light 

 and found, in the experiments made with the latter, by the 

 following confiderations. 



In a large fifli, the number of columns above mentioned, 

 contained in one eleftric organ, was found to be no lefs 

 than eleven hundred and eighty-two. This immenfe col- 

 leftion of cylinders Mr. Walfh confiders as fomewhat ana- 

 logous to a large number of jars in an eleftric battery, and 

 as containing a very large area in confequence of the great 

 number and extcnfive furface of the columns. Now it is 

 known, from experiments made with artificial eleftricity, 

 that though the eleftric matter violently condenfed, or 

 crowded into a very fmall phial highly charged, is capable 

 of forcing a paflTage through an inch of air, and that it will 

 aflbrd, in a very confpicuous mariner, the phenomena of 

 light, found, attraftion, and repulfion ; yet if the quantity 

 thus condenfed be expanded and rarefied, by communi- 

 cating it to, or dividing it aniongfl a large number of jars, 

 whofe coated furfaces conflitute a fpace, e. g. four hundred 

 times larger than that of the phial : this fame quantity of 

 eleftric matter, thus dilated, will now yield only the fainter, 

 or, if they may be fo called, the negative phenomena of the 

 torpedo. It will not now be capable of paffing over the 

 one hundredth part of that inch of air, which, in its con- 

 denfed rtate, it before fprung through with eafe ; it will not 

 now be able to jump over the little gap made in its track 

 by the interfeftion of the tin -foil ; no fpark, found, or 

 attraftion of hght bodies, will now be perceived : and yet 

 this portion of eleftric matter, in this dilated ftate, and with 

 Its elafticity thus diminiflied, will, like that of the torpedo, 

 to effeft its equihbrium, run through a confiderable circuit 

 of different conduftors, pcrfeftly continuous, and will 

 communicate a fenfible fhock. 



The Hon. Mr. Cavendifli has endeavoured to remove the 

 difficulties above ftated, firft, by fome ingenious reafonings 

 a priori, and afterwards by others drawn from the phe- 

 nomena prefented by an artificial torpedo which he con- 

 llrufted, and by means of which he has imitated the effefts 

 produced by the living animal. With refpeft to the diffi- 

 H culty 



