7 i8 



HIKKKLANO. TIIF. NORWEGIAN AURORA POLARIS KXPKniTlON, igO2 1903. 



square centimetres. A high vacuum was maintained in the vacuum-tube; the tension was over 15,000 

 volts, ami the temperature of the cathode was kept up by the current near the melting-point of platinum 



In three hours the brass anode was completely coated with a shining mirror of platinum. On the 

 glass wall of the vacuum-case there was a fairly sharp shadow of a screen that stood between the ca- 

 thode and the wall, so that in this experiment we are fully justified in speaking of "platinum rays". 



In the same way, in many and varied experiments, rays of palladium and uranium were produced 

 with the employment of as much as from 15,000 to 20,000 volts to the cathode (the positive pole was 

 earthed) and temperatures of from 600 to about 1800 C. The reader is here referred to the remarks 

 in connection with the above-mentioned experiments, in which the whole of the inner surface of the 

 vacuum-tube was greased. 



The experiments seem to show that these positive rays have several of the most characteristic 

 properties of -rays. Both the way in which they arc formed in the firm material of the cathode, and 

 the way in which they are formed in the firm material of the cathode, and the way in which they spread 



T 



D -200 



^ o 





r\ CflTHQOe 



n nnooe 



Fig. 268. 



and stop in the surrounding medium indicate this. We also succeeded in sending platinum rays, and 

 more particularly rays of metallic uranium, right through thin aluminium foil, just as can be done with a-rays. 

 We will describe two of these experiments more particularly. Rays from a small palladium cathode 

 were sent through a little hole into an otherwise closed metal capsule (which was earthed) and on be- 

 tween two parallel brass plates at a short distance from one another, as shown in fig. 268 ('). One oi 

 the plates had 200 volts, the other was earthed. After the experiment hail been going on for 3 hours, 

 the coating of palladium showed itself to be quite different upon the two plates. On the - 200 platt, 

 a long, narrow, more or less well-defined pencil of rays was found, where the precipitation was very 

 abundant. Hut in addition to this, there was a very thin coating of palladium all oi'cr this plate (which 

 was 6.5 cm. long and 4.5 cm. wide), even on the back, especially if the plate were smaller. On the 

 other plate, which was of the same size, there was a short, broad, fan-shaped precipitation of quite another 

 kind than that on the 200 plate, and there was no other deposit upon the plate, either on the front 



I 1 ) I his vacuum-tube, in several experiments, was placed between the poles of a large electro-magnet, which was just sufti 

 ciently magnetised to prevent ordinary cathode-rays from forcing their way through the hole into the otherwise closed 

 metal capsule, 



1 he discharge-current from the anode was thereby pressed by the force of the magnet into a thin, luminous cord along 

 one side of the vacuum-tube. 



Kvi-ry time during these experiments, after working for one or two hours, it appeared that palladium corpuscles from 

 the cathode were driven against the electric current right up towards the anode, the glass under the luminous cord being 

 thickly coated with a metallic band. This shows that negative palladium ions have moved up against the current. There 

 arc thus both positive and negative metal ions from the cathode. 



