266 Piqrin — Action of Vacuum Discharge Streamers. 



of the discharge increased also. With the increase of lumin- 

 osity the color of the discharge changed from the pink color, 

 which is the characteristic color of the ordinary Geissler tube 

 discharges through rarefied air, to a color which inclined more 

 and more toward the white. "With the increase of the pressure 

 the diffuseness of the discharge disappeared, but instead of the 

 diffuse pink color there appeared a beautiful green phospho- 

 rescent light which filled the whole reservoir. This phospho- 

 rescent light is so strong, that even an almost instantaneous 

 exposure is sufficient to give it time to act upon the sensitive 

 plate, as appears from the photographs in figs. 2 and 3. At 

 some future date I shall describe experiments which seem to 

 be a strong proof that phosphorescence produced by electrical 

 discharges depends on the temperature and only in so far on 

 quantity of the discharge and on the vacuum, as the tempera- 

 ture of the discharge depends on them. The investigations of 

 Crookes, Goldstein, and others lead to the conclusion that a 

 high vacuum with its cathode rays is most favorable if not 

 indispensable to the development of strong phosphorescence. 

 In my experiments a good vacuum (of about 2 mm ) gave no 

 phosphorescence whatever, whereas a poor vacuum (even with 

 as high a pressure as 100 mm ) gave very strong phosphorescence, 

 and that too not only in places where the discharge struck the 

 walls of the vessel but also in places which were far away from 

 the discharge. Presently I shall describe an experiment which 

 shows that the gas as well as the glass becomes strongly phos- 

 phorescent. My observations cannot, therefore, be well recon- 

 ciled to those of Crookes, Goldstein, etc., unless the cathode 

 rays be supposed to be very thin and very hot discharge 

 filaments. I have several experimental facts which speak in 

 favor of this hypothesis, but a discussion of them would lead 

 me beyond the limits of this paper. 



I find that some astrophysicists assume the existence of a 

 repulsive force acting between the streamers of the solar 

 corona ; it was the peculiar behavior of the corona-like vacuum 

 discharges which, in addition to other phenomena that came 

 under my observation, forced me to assume that repulsive 

 forces must be active between the filaments of these discharges, 

 although at that time I was perfectly ignorant of the details 

 of the various electrical theories of the solar corona. The 

 streamers of these discharges are very unsteady and very much 

 s]3lit up when the vacuum is poor. A photograph of a dis- 

 charge of this kind is given fig. 4. As the vacuum improves 

 the corona-like discharges become a great deal steadier, less 

 torn up and quite diffuse, but never uniformly distributed 

 over the whole spherical electrode. Fig. 5, represents the 

 photograph of a discharge in the vacuum of about 20 mm pres- 



