402 



EECENT PROGRESS IN PHYSICS. 



In one of the clamps a, the connecting wire from one pole of the'S 

 battery was screwed and in the other that leading to the tangent- j 

 compass. Between the clamps 6, the experimental wires were ex- 

 tended and this was always done before closing the battery. The con- 

 necting wires between S, H, B, Q and S, were copper wires about | 

 line in diameter, and of a total length not exceeding 5 metres, so 

 that their resistance was not considerable. 



After the wire to be experimented upon was properly inserted at E 

 and all the other connexions properly made, the circuit was closed ati 

 Q ; and, after the compass needle had come to rest, its deflection was. 

 observed and at the same time the ax)pearance of the ignition in the! 

 wire. 



The course of the experiments will become evident from the follow-^ 

 ing tables which contain the results of the observations. 



The first three sets of experiments were made with platinum w'lrt 

 of 0.45 millimetres in diameter. 



FIRSr SERIES. 

 Battery of 40 carhon-zinc cups. 



SECOND SERIES. 



Battery of 24 carhon-zinc cups. 



THIRD SERIES. 



Battery of VI carbon- zinc cups. 



Feeble, nearly throughout the whole length. 



Still feeble throughout. 



Red hot. 



Bright red. '*il[ 



