DOVE ON THE ELECTRICITY OF INDUCTION. 183 



tlie galvanometer is inserted between I and 

 III do we obtain deviation in a twofold direc- 

 tion ; with the connexions I and 11 or II and 

 III, on the contrary, a normal current, which, 

 particularly when the rotation is rapid, over- 

 powers the alternating current. If this cur- 

 rent flows from 1 to II in the galvanometer 

 which is inserted between II and I, then the galvanometer in- 

 serted between II and III indicates a deflection in the direc- 

 tion from III to II, with this peculiarity, that the deviation 

 which becomes stationary precedes a current in an opposite 

 direction on the first revolution, which is likewise obtained 

 when the keeper is turned half a revolution without being 

 rotated. 



It must however here be remarked, that in this manner, on 

 the whole, no analogous phaenomena are obtained to those which 

 have been found with other modes of trial. The production of 

 the final extra current in its full energy requires that the cur- 

 rent previously circulating in a closed metallic conductor be sud- 

 denly very much diminished in intensity, either, as in the case 

 of sparks, by an actual break in the circuit, or for physiological 

 and chemical actions by the insertion into the interrupted circuit 

 of a substance (the voltameter or the human body) offering a 

 much greater resistance to conduction. If the want of conti- 

 nuity produced at a is supplied by a galvanometer (as in the 

 connexion I and II), or if the current excited in the rotating 

 keeper remains closed by the galvanometer between I and III 

 on breaking connexion at u, then no inten-uption whatever occurs, 

 and the zero of the current is transferred to azimuth 180°. The 

 circuit is only broken in reality with the connexion II and III 

 when E is able to form. The same applies when, to avoid alter- 

 nating currents, the keeper is only turned round half a revolu- 

 tion. 



89. Now, by means of the springs 13), 14), the galvanome- 

 ter was first inserted at that moment, when the spring 3) at u 

 broke connexion once in azimuth 90°, and the keeper was kept 

 in continual rotation. The results were as follows : — 



1. Galvanometer between 8) and 15). At the break the 

 spiral is excluded from, and the galvanometer enters into the 

 connexion. This corresponds therefore with the connexion III 



VOL. V. PART XVIII. O 



