PART II. POLAR MAGNETIC PHENOMENA AND TERRELLA EXPERIMENTS. CHAP. VI. 



711 



is probable that in this case an electric disintegration of the oil on the cathode takes place, possibly 

 companied by a partial decomposition. This we conclude from the following experiment, which more- 



er is important in more respects than the one here mentioned. During our experiments, the floor 

 .id ceiling of our vacuum-box had received rather too abundant a coating of oil. In order to correct 

 is, discharges were sent through for several hours with the floor and ceiling as cathode. As these 

 ent on, the floor and ceiling became practically dry, whereas the glass walls received a powerful 

 ecipitation of oil or fatty decomposition products in a zone about 3 cm. in width, the edge on one side 

 ing somewhat diffuse, but clearly marked towards the cathode, the limit beginning on a level with 



Fig. 264. 



t: external boundary-surface of CROOKES' dark space. A similar coating also appeared upon the in- 

 sated tube by which the cathode-globe was suspended, after the corresponding drying of the globe; 

 ad the same one-sided sharply-defined coating was also found on the glass vessel that contained phos- 

 poric acid (see figure 264). 



It seems from this that just about this boundary-surface all round the cathode there is formed during 

 tl: discharge an atmosphere of complicated ions, while at the same time a high tension polarisation layer 

 i: working up and at last gives occasion for a disruptive discharge. This is also shown by the fact that 

 a ertain time always elapses before the disruptive discharges begin and then attain to a stationary con- 

 dion of frequency. The author had already put forward this assumption before the above-mentioned 

 ejeriment was made, and it will be found in a paper previously quoted here (C. R., March 17, 1913). 



The experiment seems also to indicate that a great number of the corpuscles ejected in a straight 

 lie from the cathode by disintegration are stopped again at the end of the dark space. 



Next some experiments were made in which the cathode-globe with a diameter of 24 cm. was sur- 

 Pinded with a well amalgamated zinc shell. The vacuum-box was now cleaned from oil and fat, except 

 f< a small part of one of the glass walls, where a white coating of fat remained. This patch of fat 

 gi,-e rise, as we shall soon see, to an important discovery. 



