a drop of water to impro\ e the "connection" ol a W LI e 

 lying on a metal plate, the) happened to notice gas 

 bubbles forming on the wire, and pursued the o 

 vation to the point of identifying the elo 



ill position of water into hydrogen and oxygen. 



Within two or three years innumerable electro- 

 chemical reactions had been described, some of 

 which, mil- might think, could have served as operat- 

 ing principles lor electrical instruments. Although 

 the phenomena ol i;as formation and metal deposition 

 were in fact widel) used as crude indicators ol the 

 polarit) and relative strength of voltaic piles and 

 chemical cells during the period 1800-1820 (and 

 the gas bubbles were made the basis of a telegraph 

 receiver l>\ S. I Soemmering), the quantitative 

 laws of electrolysis were not winked oul l>\ Faraday 

 until after 1830, and not until 1831 was he satisfied 

 that the electrolytic decomposition of water was 

 sufficiently well understood to he made the basis for 

 a useful measuring instrument. Describing his water- 

 electrolysis device in that year, he wrote: 



I In- instrument offers the onl) actual measurei [italics lii^l 

 of volt. tie electricit) which we at present possess I oi 

 without being at all affected by variations iii time oi 

 intensity, oi alterations in the current itself, of any kind, 

 oi from .m\ cause, oi even di intermissions of actions, 

 it takes note with accuracy of the quantity of electricity 

 which has passed through it, and reveals that quantity 

 by inspection; I base therefore named it a voltaelec- 

 ikoMi rER. ■ 



In passing, Faraday commented that the efforts 

 li\ Gay-Lussac and Thenard to use chemical de- 

 composition as a "'measure of the electricity of the 

 voltaic pile'' in 1811 had been premature because the 

 "principles and precautions" involved were not then 

 known. He also noted that the details of metal 

 deposition in electrolysis were still not sufficiently 

 understood to permit its use in an instrument.' 



The heating of the wires in electric circuits must 

 have been observed so early and so often with both 

 elet uostatic and voltaic apparatus, that no one has 

 bothered to claim or trace priorities for this "effect." 

 The production of incandescence, however, and 

 the even more dramatic combustion or "explosion"' 

 of metal-foil strips and line wires has a good deal of 

 recorded history. Among the first to burn leaf metal 



with a \olt. in pik' was |. Ii. rromsdorfl ol Erfurt 

 w I H i noted in loii | the distinctly different colors of the 

 If unes produi ei| b\ tin- \ ,ii ious common metal I 

 the succeeding lew years, Humphry Davj at the 

 Royal Institution frequently, in his public lectures, 



showed wires glowing from electrii > snt. 



I.. nl\ electrical instrumentation based on the 



ik an uiiusii.il form. Shot tl) aftei 



1800, W. II Wollaston, an English Ml)., learned 



iliod for producing malleable platinum He 



kept the process secret, and for several years i 

 an extremely profitable monopol) in the sale of 

 platinum crucibles, win-, and other objects. About 

 1810, lie invented a technique foi produi ing platinum 

 win- as Inn- .is ,i few i n ill ion ths ol an inch in diameter. 

 that has since been known as "Wollaston wire." 



Foi several years preceding 1820, no othei instrument 

 could compare the "strengths" of two voltait cells 



better than the test of the respective maximum 

 lengths of this wire that they could heat to fusion. 

 One can sympathize with Cumming's comment in 

 1821 about "the difficult) in soldering wires that are 

 barer) visible." 8 



Electrical Instrumentation, 1800-1820 



The 20 years following the announcement of the 



voltaic-pile invention were years of intense experi- 

 mental activity with this device. Many new chemical 

 elements were discovered, beginnings were made on 

 the electrochemical series of the elements, the electric 

 .in and incandescent platinum wires suggested the 

 possibilities of electric lighting, and various electro- 

 chemical observ ations ga\ e promise of other practical 

 applications such as metal-refining, electroplating, 

 and quantity production of certain gases. Investi- 

 gators were keenly aware that all of the available 

 mi .ins lor measuring and comparing the electrical 

 aspects of theii experiments (however vaguel) these 

 "electrical aspects" may have been conceived), wen- 

 slow, awkward, imprecise, and unreliable. 

 The atmosphere was such that prominent scientists 



everywhere were reach to pounce- immediately on 



any reported discovery of a new electrical "effect," 

 io explore its potentialities for instrumental purposes. 

 Into this receptive environment came H. C. ' >ersted's 



\ln ii vi i I \k\i.\\. Experimental Researches in Elti 

 vol. 1 i in i, p.ir.iiM.iph 7 in, dated January 



' Ibid., sec. 741. 



• | uu s c :i mmino, "i >n the Applicati i Mag I 



Measure of Electricity," Transactions of the Camhric/ge Philo- 

 sophical S vol 1. pp. 282 286. [Also published in 

 Philosophical M. pp. 253-257.] 



PAPER 38: EARLIEST ELECTROMAGNETIC INSTRUMENTS 



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