On the Electric Discharge in Gases. 35 



So nearly complete is the separation at 25°, that above this 

 temperature the upper stratum gives more in volume by 

 expansion by heat than it loses by the rise of the plane of 

 demarcation. To get an idea of the completeness of the sepa- 

 ration at 50° C, we may compare the volume of the lower 

 stratum at 50°, which is 8'0, with that of 7*885 grams of water 

 at 50°, which is 7 '93. This signifies that at 50° the lower 

 stratum must be nearly pure water, and the upper nearly 

 pure ethylamine. For the plane of separation stands only 

 £q of the height of the original water-column above that 

 height. See fig. 1, curve b. 



[To be continued.] 



III. On the Electric Discharge in Gases. 

 By Eilhakd Wiedemann.* 



[Plate II.] 



IN a number of previous communications f I have inves- 

 tigated the behaviour of gases under the influence of 

 electric discharges in various ways. The present research is 

 a continuation of those investigations, and is concerned with 

 (1) the effect upon the phenomena of interposing resistances 

 between the poles of the machine and the electrodes of the 

 discharge-tube ; (2) the phenomena obtained with different 

 distances between the electrodes; (3) measurements of the heat- 

 ing effect upon the gas at different points of the discharge ; (4) 

 deflection of the positive discharge ; (5) the behaviour of the 

 discharge under the influence of the magnet ; (6) the exami- 

 nation of an hypothesis as to the nature of the kathode-rays, 

 as well as (7) the nature of the positive discharge and the 

 stratifications ; (8) further observations on the influence of 

 the magnet ; (9) behaviour of bad conductors as kathodes ; 

 (10) connexion of the potential of the discharge with the 

 form of the electrodes ; and (11) remarks on the management 

 of electrophone machines. 



The great complexity of the problem explains why the 

 separate phenomena have not been hitherto sharply distin- 

 guished from each other, as, for example, the " glow " 

 appearing at somewhat higher pressures, the kathode-rays 

 which are formed at lower pressures, &c. 



* Translated from the Annalen der Physik und Chemie, vol. xx. p. 756 

 (1883), with additions and collections by the Author. 



t Wied. Ann. v. p. 200 (1878) ; vi. p. 298 (1879) ; ix. p. 157 (1880) ; 

 x. p. 202 (1880); Phil. Mag. vol. x. p. 357. The glass apparatus has been 

 made for the experiments bv Herr Gotze. 



D2 



