HENRY AND THE TELEGKAPH. 339 



opening the circuit of my large quantity magnet at Princeton, when loaded with many 

 hundred pounds weight, by attracting upward a small piece of movable wire with a 

 small intensity magnet connected with a long wire circuit. When the circuit of the 

 largo battery was thus broken by an action from a distance the weights Avould fall ; 

 and great mechanical effect could thus be jiroduced, such as the ringing of church-bells 

 at a distance of a hundred miles or more, — an illustration of which I had previously 

 given to mj' class at Princeton. . . . The object of Professor Wheatstone as I un- 

 derstood it, in bringing into action a second circuit, was to provide a remedy for the 

 diminution of force in a long circuit. My object in the process described by me was 

 to bring into operation a largo fiuautity magnet connected with a quantity battery in 

 a local circuit, by means of a small intensity magnet and an intensity battery at a 

 distance." * 



This important historic interchange of experiments and projects between Henry and 

 Wheatstone, possesses an interest and a significance quite beyond that present in the 

 contemplation of the writer. To Henry, the confidence imparted was striking only from 

 the coincidence of separate inventions in the combination or conjunction of two 

 circuits ; in his own case by the agency of an "intensity " magnet at a distance, in the 

 other case by the agency of a galvanometer needle at a distance.! But to Wheatstone, 

 how different must have been the impression aud suggestion! From the simple account 

 of Henry's contrasted "intensity" and " quantity " magnets ; of his telegraphic ex- 

 periment in 1831, — the magnetic tapping of a bell through more than a mile of line cop- 

 per wire; of his daring faith in being able to ring heavy bells by a terminal "quan- 

 tity" magnet, "af a distance of a hundred miles or more!" with what new interest and 

 meaning must the earlier and neglected researches of Henry have been recalled. Who 

 could doubt that with the unsolved problem of Mr. Cooke just fresh before him, with 

 his active and fertile mind awakened, qttick to seize upon and develop a now idea, 

 (as well illustrated in his intercourse with Mr. Cooke,) who could doubt that the pre- 

 sentation above recorded (in Aiml of 1837, ) must have been to him a new sohition and 

 a sudden revelation ? 



Surely some recognition of Henry's published researches was to be looked for in return 

 for the unexpected but unquestionable benefit conferred. We search in vain for any 

 such requital or acknowledgment. In amplifying his own " improvements" before the 

 arbitrators, he says: ^^ But the most important point of allwiismy ai>plication of the the- 

 ory of Ohm to telegraphic circuits, which enabled me to ascertain the bestproportions 

 between the length, thickness, &c., of the multijjlying coils and the other resistances in 

 the circuit, aud to determine the number and size of the elements of the battery to pro- 

 duce the maximum effect. With this law and its applications, no persons who had before 

 occupied themselves icith experiments relating to Electric Telegraphs had been acquainted" !t 

 The "theory of Ohm" (announced in 1827), had avowedly no inlluence whatever on 

 Wheatstone's researches — till after his interview with Henry, in April, 1837 ; nor was 

 the "theory of Ohm" any more definitely applied, or any more implicitly confirmed, 

 by the later English experimenter in 1837, than it had been by the earlier American 

 experimenter in 1829, and 1830. And Professor Wheatstone's exi)licit declarations that 

 in March, 1837, he found by experience that " sufficient-attractive power could not bo 



* Smithsonian Beport for 1857, pp. Ill, 112. As Prof. Alexander Dallas Bache was 

 present on the occasion above mentioned, and as he was also subsequently a Regent 

 of the Institittion, under whose direct sujiervision and authority the above statement 

 of Henry was published by the board, it may be regarded as having his imiilicit 

 corroboration. 



t Professor Wheatstone, in his "Answer" to Mr. Cooke's Pamphlet, says: "My ex- 

 periments led nie to believe that the motions of a needle could be produced at dis- 

 tances at which no effects of electro-magnetic attraction could be obtained." (Letter 

 of October 26, 1840 ; reprint, p. 114.) 



t "Professor Wheatstone's Case." The Electric Telegraph, etc. by W. F. Cooke, part 

 ii, sect. 290, p. 91. 



