DISCOURSE OF W. I!. 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 "I' an inch thick aud 80 feet 

 long stretched across the lecture-room and hack 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, dune 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 1 two differing in character as well as in direction. In these ex- 

 periments he employed a Daniell's 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 scries, 

 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 lie scarcely perceptible, 

 (although in quantity sufficient to affect the ordinary galvanometer 



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

 tin' Society for November 2d, 1838, when this memoir was rend, it is recorded " Pro- 

 fessor IIknky made a verbal communication during the course of which In- illus- 

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

 Soc. Nov. 2, 1838, vol. i. pp. 51-56.) 



t Traill experimental de C Elcctrieiti ct tin Magnetisme, vol. v. pp. 87-107. 



