Rays of Positive Electricity. 



59 



the tube ; the arrangement I was using was not suitable for 

 applying the most intense magnetic fields and I could not 

 detect that this spot was double, with one constituent 

 corresponding to the atom of nitrogen, the other to the 

 atom of oxygen. When CO was put into the tube, however, 

 the band in this region was clearly double although the 

 constituents were very close together, one constituent I 

 suppose corresponding to oxygen the other to carbon. 



One interesting feature in these experiments is that the 

 bright spots on the bands are all in the same vertical line, 

 showing that the electrostatic deflexion is the same for them 

 all, and therefore that this energy of the particles which 

 form the bright spots corresponding to the different gases 

 is due to a fall through the same potential difference. The 

 velocity of the rays forming these bright spots varies with 

 the potential difference between the electrodes. 



The bright spots come I think from the negative glow at 

 the outer boundary of the dark space ; they are weakened 

 by any arrangement which prevents the portion of the 

 negative glow straight in front of the cathode having free 

 access to the cathode. Thus, if the anode A is a disk placed 

 in front of the cathode, the spots do not appear unless the 

 anode is pushed back so as to be outside the dark space ; 

 the continuous band due to the secondary radiation is, 

 however, well developed when the anode is put forward. 

 Another interesting feature of these bright bands is that 

 some of them have negative tails connected with 

 Fig. 8. them while others have not. This is shown in fig. 8, 

 which represents the appearance in a tube con- 

 taining mercury vapour, air, helium, and hydrogen ; 

 a, b, c, d, are the spots corresponding to these 

 substances, the spot/ is on the part due to secondary 

 radiation : it will be noticed that this secondary 

 radiation has a negative tail, there are no tails 

 corresponding to the lighter elements, but the air 

 and mercury bands have a well developed tail. 



The details of the measurements of the values 

 of ejm for the different elements are given at the 

 end of this paper; it may be noted here, however, 

 that with the exception of hydrogen all the charged 

 particles of the different gases seemed to be atoms 

 and not molecules of the gas. In working with 

 the heavier atoms it is desirable to Lave very 

 •y intense magnetic fields, otherwise the magnetic 

 deflexion is very small. I am making arrange- 

 ments for experiments in which the magnetic forces will be 

 much greater than those I have hitherto used. 



f 



rx 



