DISCOURSE OF \V. B. TAYLOR. 257 



discovered the very simple solution, by a reference to the self-induc- 

 tion of the rod, — a negative wave passing, succeeded immediately 

 by a positive wave so rapidly as to completely neutralize the effect 

 upon the electroscope before the inertia <it' the gold-leaf could !»■ 

 overcome, while actually producing a double spark (sensibly co-in- 

 cident) to and from the recipient. 



A few months later, ''he had succeeded in magnetizing needles by 

 the secondary current, in a wire more than two hundred and twenty 

 feet distant from the wire through which the primary current was 

 passing, excited by a single spark from an electrical machine."* 

 In this ease the primary wire was his telegraph line stretched seven 

 years before across the campus of the college grounds in front of 

 Nassau Hall; the secondary it induction wire being suspended in 

 a parallel direction across the grounds at the rear of Nassau Hall, 

 with its ends terminating in buried metallic plates: — the large 

 building intervening between the two wires. 



This brilliant series of contributions to our knowledge of a most 



recondite and mysterious agent, placed Henry, by tl oncurrent 



judgment of all competent physicists, in the very front rank of 

 original investigators. His persevering researches in the electrical 

 paradoxes of induction, perhaps more than any similar ones, tended 

 to strengthen the hypothesis of an setherial dynamic agency; although 

 he himself had lor a lone,' time been inclined to favor the material 

 hypothesis, f 



INVESTIGATIONS IX GENERAL PHYSICS: FROM 1830 TO 1846. 



In order to give a proper connection to the experimental inqui- 

 ries undertaken by Henry in various tields, it is accessary to pause 

 here, and to recur to some of his earlier scientific labors, — l>ce.in- 

 ning again at Albany. 



* Proceedings Am. Phil. Soc. Oct. 21, 18J2, vol. ii. p. 229. It is barely possible that 

 tin- primary current might have returned through tin- second wire. 



tin a paper "On the Theory of the so-called Imponderables" published some 

 years later, in referring to the phenomena of electrical oscillation in discharge, ami 

 of tlie series of inductions taking place ami "extending to a surprising distance on 

 all sides," he remarks: "As these are the results of currents in alternate directions, 

 they must produce in surrounding space a series of plus and minus motions, anal- 

 ogous to— if not identical with undulations." Proceed. Amer. Association Albany 

 Aug. 1851, p.89.) 



IT 



