DISCOURSE OF W. B. TAYLOR. 227 



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

 elements,) was shown to have the singular capability (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 must 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 very long con- 

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

 This was a very important though unconscious experimental con- 

 iirmation 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, t 



Never should it be 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 creator 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 tliat its magnetic power could be 

 called into operation by an 'intensity' battery; and hy a quantity magnet, a piece 

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

 fully developed by a 'quantity' battery." [Smithsonian Report for 1857, p. 103.) 

 These terms though somewhat antiquated and generally discarded by recent 

 Avriters, are still very convenient designations of the two classes of action, both 

 in the battery and in the magnet. See "Supplement," Note B. 



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

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

 resistance of a long conductor ; but the magnetizing effect has not been found to 

 be diminished in the ratio of its length. In a very long wire, the magnetizing 

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

 to the square of the length of the conductor. 



IGeobg Simon Ohm, professor in physics at Munich, published at Berlin, in 

 1827, his "Galvanische Kette, mathematisch bearbeitet:" and in the following 

 year, he published a supplementary paper entitled "Nachtrage zu seiner mathe- 

 matischen Bearbcitung der galvanischen Kette ;" in Kastner's Archiv filr gesammte 

 Naturlehre: (8vo. Niirnberg:) 1828, vol. xiv. pp. 475-493. Fourteen years after the 

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

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

 tigated mathematically." Taylor's Scientific Memoirs, etc. London, 1841, vol. ii. 

 pp. 401-506.) 



