738 Dr. Gwilym Owen and Mr. R. Halsall on Carriers 



are given in purely arbitrary units, and as the sensitiveness 

 of the electrometer or of the galvanometer was altered con- 

 tinually to suit the varying magnitudes of the thermionic 

 currents at the different temperatures, it is only numbers in 

 the same horizontal line in columns 3 and 4 tbat are to be 

 compared. It should also be explained that O'l in the fourth 

 column means a deflexion on the scale of one-tenth of a 

 millimetre. In the experiments with platinum and iridium 

 the vacuum was maintained by means of charcoal in liquid 

 air. 



Metal. 



Temperature, 



Negative thermionic current 

 in arbitrary units. 



Proportion of 

 heavy ions 

 to electrons. 



Magnetic field off. 



Magnetic field on. 



r 



Palladium 

 (pure) 1 



Dull red. 

 Bright red. 

 Yellow. 

 Bright yellow. 



l-'OO 

 45000 



800 

 7G00 



<01 



3 

 <01 



o 



< 1 in 14000 

 1 in 15000 



<1 in 8000 

 1 in 3500 



Platinum j 

 (pure) | 



Bright yellow. 

 Almost white hot. 

 Nearly melting. 



200 



500 



33000 



<01 



3 



< 1 in 2000 



< I in 5000 



1 in 11000 



Platinum J 

 (commercial) j 



Bright yellow. 

 Very bright yellow. 

 While hot. 



600 



2(>oo 

 4200 



<0'1 

 1 

 1*5 



< 1 in 6000 

 1 in 2600 

 1 in 2800 



Iridium J 

 (piwe) ........ | 



Bright yellow. 

 White hot. 

 Nearly melting. 



580 

 1500 

 5400 



<01 



<01 



1 



< 1 in 5800 



< 1 in 15000 



1 in 5400 



In every case control tests were made by charging the 

 wires positively, when it was found that the strongest 

 magnetic field we could apply (about 3000 units) was 

 entirely without influence on the positive carriers. 



The above table shows clearly that the proportion of heavy 

 ions to electrons in the negative thermionic current is ex- 

 ceedingly small at all temperatures for the metals investi- 

 gated. This fact is specially interesting in the case o£ 

 palladium, which metal, as has been mentioned, volatilizes 

 rapidly in a vacuum. Since in every case the thermionic 

 current with the magnetic field on could only produce 



