DISCOURSE OF W. B. TAYLOR. 251 



fifteen inches, and with a still larger battery and longer conductors, 

 no change was found although the induction was produced at the 

 distance of several feet." With Dr. Hare's battery of 32 one-gallon 

 jars, and a copper wire about one-tenth of an inch thick ai;d 80 feet 

 long stretched across the lecture-room and back on either side toward 

 the battery, a second wire stretched parallel with the former for 

 about 35 feet and extended to form an independent circuit, (its ends 

 being connected with a small magnetizing helix,) was tested at vary- 

 ing distances beginning with a few inches until they were twelve 

 feet apart: at which distance of the parallel wire, its induction 

 though enfeebled, still indicated by its magnetizing power, a direc- 

 tion corresponding with the primary current. The form of the 

 room did not permit a convenient separation of the two circuits to 

 a greater distance.* 



The eminent French electrician Antoine C. Becquerel, in a chap- 

 ter on Induction in his large work, remarks: "Very recently M. 

 Henry, Professor of Natural Philosophy in New Jersey, has extended 

 the domain of this branch of physics : the results obtained by him 

 are of such importance, particularly in regard to the intensity of 

 the effects produced, that it is proper to expound them here with 

 some detail." Twenty pages are then devoted to these researches. f 



A memoir was read before the Society, June 19th, 1840, giving 

 an account of observations on the two forms of induction occurring 

 on the making and on the breaking of the primary galvanic circuit, 

 the two differing in character as well as in direction. In these ex- 

 periments he employed a DanielPs constant battery of 30 elements ; 

 the battery being "sometimes used as a single series with all its 

 elements placed consecutively, and at others in two or three series, 

 arranged collaterally, so as to vary the quantity and intensity of 

 the electricity as the occasion might require." As the initial induc- 

 tion had always been found so feeble as to be scarcely perceptible, 

 (although in quantity sufficient to affect the ordinary galvanometer 



* Trans. Am. Phil. Soc. t vol. vi. (n. s.) art. ix. pp. 303-337. In the Proceedings of 

 the Society for November 2d, 1838, when this memoir was read, it is recorded "Pro- 

 fessor HENRY made a verbal communication during the course of which he illus- 

 trated experimentally the phenomena developed in his paper." (Proceed. Am. Phil. 

 Soc. Nov. 2, 1838, vol. i. pp. 54-56.) 



t Traits experimental de V HZectricite et du Magnetisme, vol. v. pp. 87-107. 



