106 DOVE ON THE ELECTRICITY OF INDUCTION. 



a magnetic needle placed near the conductor would be deflected, 

 but a human body causing the neutralization would not suffer 

 any shock ; if the leaves collapsed suddenly, on the contrary, a 

 shock would be felt, whilst the magnetic needle would remain 

 unmoved. 



To these differences between the physiological and galvano- 

 metric action of the same quantity of electricity, according as it 

 circulates more or less quickly through a conductor which have 

 here been established, others may be added. In the electric 

 currents produced by the motion, of a closed conductor in the 

 proximity of a magnet, the power is directly proportional to the 

 velocity, the duration is inversely as the velocity ; the tendency 

 of a needle to move when placed in any fixed direction with 

 respect to the coils of the multiplier during the continuation 

 of the current is therefore entirely independent of the velocity, 

 as Gauss has already shown *. The physiological impression is 

 however not a product of the power and the duration, but is 

 chiefly determined by the former : it increases therefore with the 

 velocity of the motion, without affording to the person suflfer- 

 ing the shock, by the shorter duration of a painful sensation, a 

 full compensation for its increased acuteness. 



Similar determinations to those relating to the physiological 

 action of the current are likewise available for its property of 

 magnetizing hardened steel; for if a Leyden jar be gradually dis- 

 charged by a point or a rod of ivory, according to Seebeck's ob- 

 servation t, the magnetism produced in a steel needle by the 

 connecting wire is either quite imperceptible or much less in- 

 tense than when the discharge is effected in the usual manner 

 by a discharger ending in a knob. 



When therefore, of two currents produced in the same con- 

 ductor, one of which has been induced by an electro-magnetized 

 bar of iron, the other by an electro-magnetized bundle of loires, 

 and both causing the same deviation in the galvanometer, the 

 latter exhibits more poiverful physiological action and more vivid 

 sparks than the former, and at the same time magnetizes steel 

 more intensely, we may conclude that in the latter an equal 

 quantity of electricity is passing in a shorter time than in the 

 former, and, on the contrary, the physiological and magnetizing 

 action of both cun'ents being equal, that that one which affects 



* Schumacher's jhtroiiomischcs Jahrbuch, ISiJfJ, p. 12. 



\ Magn.d. galv. Kctte, p. 15; Abhau<llungen dciBerliin'r Akudemie, 1821. 



