under the Influence of the Electric Discharge, 413 



of about 40 centims., that without altering the connexions 

 it could be brought between the electrodes or removed. In 

 the former position it intercepted the kathode-rays issuing 

 from the negative electrode, whilst in the latter they had a free 

 path. The intensity of the current was the same in both cases. 



7. Reitlinger* has shown that when stratifications form 

 about the positive electrode in a tube traversed by a current, 

 their number is considerably increased by the approach of a 

 magnet from the negative pole. The increase is caused by the 

 advance of those nearest the negative electrode, and the ap- 

 pearance of new ones at the positive pole. I have observed 

 that the mean distance of the layers is not much altered in the 

 process. When, by carrying the exhaustion far enough, all 

 the stratifications have been made to disappear, I have suc- 

 ceeded in producing new ones by approaching a magnet to 

 the electrode. The phenomenon is especially beautiful when 

 the positive electrode is a point ; the stratifications seem then 

 to float up round it. 



The phenomena are seen most distinctly when the quantities 

 of electricity passing in the discharge correspond accurately 

 to the potential necessary to cause discharge through the tube, 

 and are not increased by interposition of air-sparks in the 

 circuit. 



Action of different Sources of Electricity. 



The conditions of discharge are certainly the most simple 

 in friction- or electrophorus-machines. The electricity is pro- 

 duced uniformly, it flows into the electrodes, after a cer- 

 tain time reaches the potential necessary to discharge, and 

 discharges itself, and the process begins anew. So little elec- 

 tricity is collected upon the disks, conducting-wires, &c, or 

 the flow of electricity is so rapid, that the discharge may be 

 considered almost instantaneous. It is only in quite excep- 

 tional cases at very low pressures that we see sometimes how 

 a discharge is made up of a series of partial discharges. 



But for our investigations we must have such instantaneous 

 discharges ; for only with such can we assume that the dis- 

 charge gives up its energy to the gas so rapidly that no per- 

 ceptible transference of energy from the gas to its envelope 

 takes place during the process. 



The quantities of electricity produced by Topler's machine 

 are abundantly sufficient for all thermic measurements, while, 

 on the other hand, they are not so great that the images of the 

 separate discharges cannot be distinguished in the revolving 



* Reitlinger, Wien. Anz. p. 795 (1876). 



