/ DISCOURSE OF W. B. TAYLOR. 243 



conductor produces ho\yever, little or no increase of effect when 

 introduced into a galvanic circuit of considerable intensity." When 

 for example an "intensity" battery of two Cruickshanks troughs, 

 €ach containing fifty-six elements was employed wuth the larger 

 copper spiral, "no greater effect was perceived than with a short 

 thick wire:" in either case, only a feeble spark being given.* An 

 abstract of the results thus announced, (and which were obtained 

 by Henry during the summer of 1834,) was communicated by 

 Dr. A. D. Bache, as a Secretary of the American Philosophical 

 Society, to the Franklin Journal, in order to give these interesting 

 facts an earlier currency. f The date of original discovery was 

 however so well established, that this friendly effort was scarcely 

 necessary. | 



Combined Circuits. — In 1835, wires had been extended across 

 the front campus of the college grounds at Princeton from the upper 

 story of the library building to the Philosophical Hall on the oppo- 

 site side, through which signals were occasionally sent, distinguished 

 by the number of taps of the electro-magnetic bell, as first exhib- 

 ited five years previously in the hall of the Albany Academy. It 

 has already been noticed, that contrary to all the antecedent expec- 

 tations of physicists, Henry had established the fact that the most 

 powerful form of magnet (designated by him the "quantity" 

 magnet) is not the form best adapted to distant action through 

 an extended circuit. The ingenious idea occurred to him that 

 notwithstanding this fundamental fact, it would be quite easy to 

 combine the two systems so as to enable an operator to produce the 

 most energetic mechanical effects, at almost any required distance. 

 It is simply necessary to employ with the distant "intensity" 

 magnet an oscillating armature with a suitable prolongation so 

 arranged as to open and close the short circuit of an adjoining 



* Trayis. Am. Phil. Soc. vol. v. (n. s.) art. x. pp. 223-231. 



^Journal of the Franklin Institute, March, 1835, vol. xv. pp. 1G9, 170. See "Supple- 

 ment," Note E. 



JM. Becqtjerel in his elaborate Treatise on Electricity, in the chapter on "The 

 influence of an electric current on itself by inductioc," says with i-egard to the 

 increase of tension in a feeble current when passing through a long spiral conductor, 

 "The efljects observed in these circumstances appear to have been noticed for the 

 first time by Professor Henry." (Traits experimental de V&.ectricit& et du Magnetisme, 

 «vo. 7 vols. Paris, 1824-1840, vol. v. art. 1261, p. 231.) 



