PHILOSOPHICAL SOCIETY OF WASHINGTON, 26 T 



tongue. With two elements in the circuit the shock at the 

 beginning was slightly increased : with three elements the in- 

 crease was more decided, while the shock at breaking the circuit 

 remained nearly oC the same intensity as at first, or was compa- 

 ratively but little increased. When the number of elements was 

 increased to ten, the shock at making contact was found fully 

 equal to that at breaking, and by employing a still greater num- 

 ber, the former was decidedly greater than the latter, the difference 

 continually increasing until all the thirty elements were introduced 

 into the circuit. , . . Experiments were next made to deter- 

 mine the influence of a variation in the length of the coil, the 

 intensity of the battery remaining the same." For this purpose 

 the battery consisting of a single element " was employed ; and 

 the length of the copper ribbon coil was successively reduced 

 from 60 feet, by measures of 15 feet. With 45 feet, the initial 

 induction was stronger than with 60 feet : with the next shorter 

 length it was more perceptible, and increased in intensity with 

 each diminution of the coil, until a length of about fifteen feet 

 appeared to give a maximum result." At the same time it was 

 found that " the intensity of the shock at the ending of the bat- 

 tery current diminishes with each diminution of the length of 

 the coil. ... By the foregoing results we are evidently 

 furnished with two methods of increasing at pleasure the intensity 

 of the induction at the beginning of a battery current, the one 

 consisting in increasing the intensity of the source of the elec- 

 tricity, and the other in diminishing the resistance to conduction 

 of the circuit while its intensity remains the same." 



Having thus succeeded in exalting the initial induction, Henry 

 proceeded in his investigation. Distinct currents of the third, 

 fourth, and fifth orders were readily obtained from it ; and as was 

 anticipated, with their signs (or directions) the reverse of the 

 corresponding orders derived from the terminal induction. In 

 other respects "the series of induced currents produced at the 

 beginning of the primary current appeared to possess all the 

 properties belonging to those of the induction at the ending of 

 the same current." 



In the course of these investigations the idea having occurred 

 to him "that the intense shocks given by the electricnl fish may 

 possibly be from a secondary current," as it appeared to hira 

 that "this is the only way in which we can conceive of such 

 intense electricity being produced in organs imperfectly insulated 

 and immersed in a conducting medium," he endeavored to simu- 

 late the effect by arranging a spcondary wire coil furnished with 

 terminal handles, over a primary copper ribbon coil, the two 

 being insulated as usual. "By immersing the apparatus in a 

 shallow vessel of water, the handles being placed at the two ex- 

 tremities of the diameter of the helix, and the hands plunged 



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