DISCOURSE OF \V. !;. TAYLOR. 22"3 



and feebler system (requiring for its action a battery of numerous 

 elements,) was shown to have the singular capability i never before 

 suspected nor imagined) of subtile excitation from a distant source. 

 Here for the first time is experimentally established the important 

 principle that there inusi be a proportion between the aggregate 

 internal resistance of the battery and the whole external resistance 

 of the conjunctive wire or conducting circuit ; with the very impor- 

 tant practical consequence, that by combining with an "intensity" 

 magnet of a single extended fine coil an "intensity" battery of 

 many small pairs, its electro-motive force enables a verv long con- 

 ductor to be employed without sensible diminution of the effect. 51 

 This was a verv important though unconscious experimental con- 

 firmation of the mathematical theory of Ohm, embodied in his 

 formula expressing the relation between electric flow and electric 

 resistance, which though propounded two or three years previously, 

 failed for a long time to attract any attention from the scientific 

 world, f 



Never should it he forgotten that he who first exalted the "quan- 

 tity" magnet of Sturgeon from a power of twenty pounds to a 

 power of twenty hundred pounds, was the absolute creatok of the 

 "intensity" magnet; and that the principles involved in this crea- 

 tion, constitute the indispensable basis of every form of the electro- 

 piece of soft, iron so surrounded with wire thai Its magnetic power could be 



called into operation by an 'intensity' battery; and bynquantity magnet, a pi 



of iron so surrounded by a number of separate coils that its magnetism could be 

 fully developed by a 'quantity' battery." (Smithsonian Report tor 1S57, p. 103.) 

 These terms though somewhat antiquated and generally discarded by recenl 

 *a riters, are still very convenient designations of the t wo classes of action, both 

 in tin- battery and iii tin- magnet. See "Supplement," Note B. 



: Beyond a certain maximum length there i* of course, a decrease of power for 

 each particular coil of tin* "intensity" magnet, proportioned to the increased 



resist! if a long conductor; hut the magnetizing effect has not turn found to 



In- diminished in tin-' ratio of its length. In a very long win', the magnetizing 

 influence (with a suitable "intensity " battery) appears to be inversely proportioned 

 to tin' square of iln' length of tin' conductor. 



tGeorg Simon Ohm, professor in physics ;it Munich, published at Berlin, in 

 1827, his "Galvanische Kette, mathematisoh bearbeitet:" and in tin' following 

 year, In- published a supplementary paper entitled "Xachtrage zu seiner mathe- 

 matisehen Bearbeitung dcr galvanisehen Ivctte;" in Kastncr's Archiv fiir gesanunte 

 Xaturlehre: l8vo. NUrnberg:) 1S2S, vol. xi\. pp. 175-193. Fourteen years after the 



publication of the former memoir, this elaborate discussion was for the first I 



translated into English, by Mr. William Francis. ("The Galvanic Circuit inves- 

 tigated mathematically." Taylor's Scientific Memoirs, etc. London, 1st], vol. ii. 

 pp. 401-506.) 



