170 Dr. Faraday's Experimental Researches in Electricity. 



and finally, when the battery had been positively charged by 

 about forty turns of the machine, it was discharged by the 

 rod and the thread through the galvanometer. The needle 

 immediately moved. 



297. During the time that the needle completed its vibra- 

 tion in the first direction and returned, the machine was 

 worked, and the battery charged; and when the needle in 

 vibrating resumed its first direction, the discharge was again 

 made through the galvanometer. By repeating this action a 

 few times, the vibrations soon extended to above 40° on each 

 side of the line of quiescence. 



298. This effect could be obtained at pleasure. Nor was 

 it varied, apparently, either in direction or degree, by using 

 a short thick string, or even four short thick strings in place 

 of the long fine thread. With a more delicate galvanometer, 

 an excellent swing of the needle could be obtained by one 

 discharge of the battery. 



299. On reversing the galvanometer communications so as 

 to pass the discharge through from B to A, the needle was 

 equally well deflected, but in the opposite direction. 



300i The deflections were in the same direction as if a vol- 

 taic current had been passed through the galvanometer, i. e. 

 the positively charged surface of the electric battery coincided 

 with the positive end of the voltaic apparatus (268.), and the 

 negative surface of the first with the negative end of the 

 latter. 



301. The battery was then thrown out of use, and the com- 

 munications so arranged that the current could be passed from 

 the prime conductor, by the discharging rod held against it, 

 through the wet string, through the galvanometer coil, and 

 into the discharging train (292.), by which it was finally di- 

 spersed. This current could be stopped at any moment, by 

 removing the discharging rod, and either stopping the ma- 

 chine or connecting the prime conductor by another rod with 

 the discharging train; and could be as instantly renewed. 

 The needle was so adjusted, that whilst vibrating in moderate 

 and small arcs, it required time equal to twenty-five beats of 

 a watch to pass in one direction through the arc, and of course 

 an equal time to pass in the other direction. 



302. Thus arranged, and the needle being stationary, the 

 current, direct from the machine, was sent through the 

 galvanometer for twenty-five beats, then interrupted for 

 other twenty-five beats, renewed for twenty-five beats more, 

 again interrupted for an equal time, and so on continually. 

 The needle soon began to vibrate visibly, and after several 



