Organs of Ele&r'ic Fijlj. 3S7 



condu£lors to be as the length of the fpark, which, though a doubtful pofitiou hi great in- 

 tenfities, may ferve the prefent occafion, and that a talc ele£trophore of two fquare inches 

 furface on each fide have the intenfity to give a fpark of one-tenth of an inch, its whole 

 ele£tricity will be esiprefled by 4 X o,i = 0,4.. But the whole ele£lrlcity of the conduftor 

 which gave the nine inch fpark will be exprefled by 6 X 144 X 9 = 7776- And this num- 

 ber doubled, or 15552. for a double ele£lrophore, Mo exprefles fuch a charge of the talc as 

 gives a fpark of explofion or difcharge of 0,1 inch. The length of the explofive fpark, on 

 applying fuch a iimple eleflrophore to its plate, will therefore be fliorter than 0,1 in the 

 proportion of 0,4 to 15552, or i to 38S80 ; the fpark would therefore be the ,000002 of 

 an inch long. And as Mr. Cavendilh has found that eledlric fliocks nearly equal are pro- 

 duced when the quantities of eleQricity are inverfely as the lengths of the fpafk of dif- 

 charge, and alfo that the quantities of ele£lricity in charges are as the furfaces, it will fol- 

 low, that the fliock of two fquare inches of the talc with a fpark of 0,1 inch, will be equal 

 to the fhockof 77760 fquare inches with a fpark of 0,000002 inches. This furface is equi- 

 valent to an ele£trophore of 279 inches fquare, or meafuring 23 feet by the fide ; or 

 19440 of the double ele£lrophores of two inches furface. 



To elucidate this, I conftrufted a fmall eleftrophore adapted to perform the experiments 

 which Beccaria called vindicating eleflricity. It confifted of two metallic plates with in- 

 fulating handles. Each was a fquare whofe fide meafured two inches, and the face of each 

 was coated with the thin talc. When the two uncovered furfaces of the talc were applied 

 together, and :he whole charged as one plate, the difcharge gave a denfe fhock of con- 

 fiderable feverity. The fparks, on feparation, were about one-eighth of an inch long, and 

 very weak. No perceptible fpark was exhibited on bringing them together. The opera- 

 tion appeared capable of being repeated almoft inceffantly, as in the eleiSrophore. 



It may perhaps be fimpler to confider the elcQrophore as a compound jar or plate variable 

 in its thicknefs. When the plates of the inflrument jufl; defcribed arc together, the two 

 eleclricities on the contiguous furface compenfate each other, and the external coatings 

 may be fuppofed nearly in the natural Hate. But when they are feparated, the portion of 

 compenfatcd eleiSlricity will be lefs, and the intenfities would rife if it were not for the ex- 

 ternal coatings, which in a great meafure prevent it; each glate becoming charged like a 

 fimplejar, and the equilibrium being polTiblc to be reRored by communication between the 

 external coatings. This fecond charge, intenfity, and explofion will be greater the further 

 the plates are removed. It appears, therefore, that in a deduftion of the manner in which 

 cledric fifh may communicate the {liock, we may fafely avoid the more complicated con- 

 Cdcration of the eledrophorc, and compare the a£lion immediately to that of a fimplejar. 

 Mr. Hunter, in the 63d volume of the Pliilofophical Tranfactions, page 434, defcribes 

 the eleilric organ of the torpedo to confift of a number of columns varying in their length 

 from an inch and an half to a quarter of an inch, and their diameters about 2-ioths of an inch. 

 The number of columns in each organ of the torpedo lie prcfcntcd to the Royal Society was 

 about 470; but in a very large torpedo the number of columns in one organ was 11S2. 

 Thcfc columns were compofcd of films parallel to tlic bafe of each, and the diftance be- 

 tween each partition of tlie columns was i-l5oth of an inch. If we fuppofe thefe films 

 to be charged with cleflricity, and to be i-300th of an inch thick ; and a middling fize tor- 

 pedo to contain in boUi organs on the whole icoo columns of an inch long, and o,oj 



fquare 



