136 Prof. J. C. Poggendorff on the Induction Apparatus 



conducted through the coils of the other, in order to study the 

 influence of increased resistance npon tlie sparks and luminous 

 phjeuomena in general. For this purpose I conducted the current 

 of the shorter of ray induction wires through the 20,000 feet of 

 wire in the other two coils. The sparks were smaller and less 

 brilliant, but there was no perceptible diminution in the distance 

 at which sparks could be obtained. The additional introduction 

 of twelve beakers full of water, and connected by platinum arches, 

 did not alter this result. 



This corresponds perfectly with similar phsenomena in frictional 

 electricity, formerly studied by Riess. Nevertheless, as far as 

 my own experiments are concerned, I am inclined to doubt 

 whether the tension is the same at all points of the long and 

 well-insulated wire circuit ; for when I loosened one end of this 

 circuit from the active induction coil, and by means of another 

 wire, led it alongside the other end of the circuit near to the 

 pole with which it was still connected, sparks were visible 

 between them when the other pole was connected with the earth. 



The instruments can be connected alongside one another, or 

 one before the other, in order to study the influence of the thick- 

 ness and length of the wire. 



I had here an opportunity of testing an assertion of Masson's. 

 This physicist states that when two induction instruments are 

 placed alongside one another, but in opposite directions, and are 

 thus connected with the electric egg, both electric lights, the blue 

 glimmering light and the positive flame, are simultaneously seen 

 upon each knob*. From this he arrives at the strange conclu- 

 sion, that rarefied air possesses the property of simultaneously 

 conducting two electric currents of opposite directions. I ob- 

 tained a difi'erent and far more natural result, viz. that under 

 the circumstances no light whatever is visible. Masson was 

 probably led to his conclusion by allowing two complete instru- 

 ments to work against one another, and it is more than probable 

 that the strokes of the hammers of both instruments were not 

 exactly isochronous and synchronous. The phaenoraenon observed 

 by him would then be a natural consequence. Such could not 

 be the case in ray experiment, for the inducing wires of both 

 coils formed, one after the other, a single circuit, which was 

 broken by a single hamraer. 



In conclusion I will notice a combination, the experiments 

 with which are calculated to furnish indications relative to the 

 construction of such apparatus. 



Two instruments, A and B, were so combined that the current 

 * Comptes Rendus, vol, x.\xvi. p. 256, and vol. xxxvii. p. 849. 



