472 



ELECTRICITY. 



xl on taking such an apparatus to piece* after it had 



.on.-tructed thirty months no trace of oxidation 

 was c\ uli nt on the zinc plate*. 



I have i, .niicd nm\c column* of very extraordinary 

 " power, by \arious novel methods of combination ; and 

 am. " ve noticed come very singular phenomena during va- 

 rious < \periinents on this subject, in which I am -till 

 engaged, hut the results arc not yet sufficiently mature 

 for publication. 



The bize of the plates in the column need not be large. 



I have constructed tin in of various sizes, and find no 



proportionate advantage by extending the diameter be- 



i litlis of an inch. They may even be con- 



iniieh smaller than this. 



I5y connecting the extremities of a column (if at 



M iii - w ith the opposite coatings of a Leyden jar, 

 during a period of from one to five minutes, a char:, 

 usually coinniunicated to it, capable of affording .1 siu.ill 

 but distinct spark, when the discharge is made by a wire 

 that is not very thick. 



The most extensive series I have yet made experi- 

 ments with, consisted of 20,000 groups of silver, zinc, 

 and double discs of writing p:iper. Its power was con- 

 siderable. 1'ith bull electrometers, with balls of one- 

 fifth of an inch diameter, and threads of four inches 

 lung, diverged to the distance of two inches and up- 

 wards, when connected with its opposite extremities. 

 An electrometer at the centre was not affected. When 

 either extremity of the column was connected with the 

 ground, the electrometer attached to that extremity clo- 

 sed, and the central electrometer opened with the same 

 electricity, whilst that connected with the opposite, ex- 

 tremity had its original divergence considerably incrca- 



1 ; but the electro- motion was so slow, that some mi- 

 nutes were required to produce the full effect. 



By connecting one extremity of the series with a fine 

 iron wire, and bringing the end of this near the other 

 extremity, a slight layer of varnish being interposed, a 

 series of minute bright sparks were obtained, by draw- 

 ing the point of the iron wire lightly- over the varnished 

 -urt'ace. 



A jar containing fifty square inches of coated surface, 

 was charged by ten minutes contact with the column, 

 so as to convey a disagreeable shock, felt distinctly in 

 die elbows and shoulders, and by some individuals 

 across the breast. 



The charge from this jar could perforate thick draw- 

 ing-paper, but not a card. It had just power to fuse 

 one inch of platina wire, of the five thousandth of an 

 inch diameter. 



Notwithstanding the considerable electric power of 

 thiscombination, it had not the slightest chemical action; 

 neither the best nor worst com! net i HIT media were affect- 

 ed. Saline compounds, tinged with the most delicate 

 \cgetablecolours, were exposed under the most favour- 

 able circumstances to its action, and, in some instances, 

 i'or many days, but no chemical effect was produced. 



It therefore appears indispensibly necessary to the 

 chemical power of the Voltaic apparatus, that a liquid 

 he interposed between each pair of its plates ; whilst 

 for the pure electrical effects, the only condition ap- 

 pears to be the association of the t\vo metals, and the 

 connection of the different pair-, by some conductor 

 that does not interfere with their electro-motive power. 



1 am now constructing, and have nearly completed, 

 an addition to the above series of columns, which will 

 form n arrangement together of 60,000 groups. It 

 was not possible for me to make the experiments with 

 ihcrn in time for this publication ; but my princi ; 



trillion is to ascertain if any chemical effect can be pro- 

 duced by the most powerful column. If it cannot, I 

 think the assigned condition lor chemical action iim-t 

 be considered as established ; and the determination of 

 this circumstance, will !* one step towards a c. 

 theory of Voltaic electricity." 



For farther information on this subject, see l)e I, up, 

 'M>\ Journal, 1S10, vol. xxvii. p. SI, Kil, and 

 '-'11. /,/. 1 s 1 1 . vol. xxviii. p. .",. M. M. Forster, Phi- 

 lampkicil Magazine, 1810, vol. xxxv. p. -Jn."., .','17 

 Id. 1810, vol. xxxvi. p. 7.5,317, IT '. / /. xxxvii. p. 

 1<)7. Singers' ElcmetiUof Eltdruity, p. -US) ; and Ap- 

 pendix, Art. 11. p. 478. 



SECT. VI I. On the Electricity exhibited by some Fishes. 



As there is yet no reason for believing, that the elec- M, 

 tricity exhibited by several fMie.> is the result of any of- 

 chemical action, the consideration of this curious subject 

 belongs more properly to electricity than to galvanism. 

 There are only five fishe* which are known to IK- capa- 

 ble of giving the electric shock, namely the Rnia tor* 

 jtfilo, the (iym'toins rlectiicux, the fiiliirus elcclricus, 

 the Tric/iiuriis Indicus, and the Tctruodon. 



1. On the Electricity of the Raia Torpedo. 



The remarkable property of this fish to produce a on the dec- 

 sensation of numbness on those who touch it, was triciiy of 

 known to Aristotle and Pliny, who considered it as a << 

 mode of defence against fish of a large size, and as a tur P cdo - 

 method of catching the smaller fi~h, upon which it sub- 

 sisted. Oppian informs us, that the torpedo, when 

 caught by the hook, exerts itself in such a manner, that 

 its influence passing along the line benumbs and stupi 

 fies the fisherman. 



Nil Uil HI MCfKK, &C. 



The hooked torpedo, with instinctive force, 

 ('.ills all his magic from its secret source : 

 Quick through the slender line and polished wand 

 It darts, and tingles in th' ofl'endtng hand. 

 The palsk-d fisherman, in dumh surprise. 

 Feels through his frame the. cliillinv; i..| "i li^c ; 

 Drop.* the lost rod, and seems in stiffening pain, 

 Some frost-fixed wanderer on the polar plain. 



Among modern naturalists, it appears to have l>cen fin* 

 observed in the year 1(>7() by liedi, who relates, that it 

 was a prevailing ,opinion among the fishermen, that 

 the shock of the torpedo was communicated to the 

 hand and arm of the person catching the fish, by 

 means of the line and rod to which it was suspend- 

 ed. A few years afterwards, the anatomy of this ant. 

 mal was examined by I.oren/ini, who published en- 

 gravings of its electrical organs. From this benumb- 

 ing faculty, the fish received the name of Torpedo; 

 and while the philosophers of F.urope were peq>lexing 

 themselves about the cause of this extraordinary proper- 

 ty, the Arabians had identified its action with that of 

 atmospherical electricity, by giving it the name of raad, 

 or max/I, which ii, their language signifies lightning. 



KiMinnur seems to have been the first philosopher, obwrva- 

 who examined with any thing like accuracy the proper- tions of 

 tie> i-f tho torpedo ; but he committed a great mistake Reaumur. 

 in ascribing them to tho force of its muscles. He ob- 

 served, that when the torpedo wished to exercise it* 

 electrical organ-, it first sensibly diminished the curve 

 on its back, till the surface became flat, or even con- 

 cave, and then by a sudden motion it raised it again to 

 its former convexity. If the fish in this state 



