586 



Professor J. J. Thomson 



[March 22, 



quently the values of -, will be smaller than if the particle had re- 

 tained its charge during the whole of its career. Thus, suppose that 

 some of the particles constituting the positive rays, after starting 

 with a positive charge, get this charge neutralised by attracting to 

 them a negatively electrified corpuscle, the mass of the corpuscle is 

 so small in comparison with that of the particle constituting the posi- 

 tive ray that the addition of the particle will not appreciably diminish 

 the velocity of the positive particle. Some of these neutralised 

 particles may get positively ionised again by collision, while others 

 may get a negative charge by the adhesion to them of another 

 corpuscle, and this process might be repeated during the course of 

 the particle. Thus there would be among the rays some which were 

 for part of their course unelectrified, at other parts positively electri- 

 fied, and at other parts negatively electrified. Thus the mean value 



of - might have all values ranging from a, its initial value, to - a', 



where a might be only a little less than a. This is just what we 

 observe, and when we remember that the gas through which the rays 

 are passing is ionised, and contains a large number of corpuscles, it 

 is, I think, what we should expect. 



At very low pressures, when there are very few ions in the gas, 

 this continuous band stretching from the origin is replaced by dis- 

 continuous patches. 



Positive Rays in Hydrogen. 



In hydrogen, when the pressure is not too low, the brightness of 

 the phosphorescent patch is greater than in air at the same pressure ; 

 the sliape of the deflected phosphorescence is markedly different from 

 that in air. In air, the deflected phosphorescence is usually a straight 



Fig. 7. 



Fig. 8. 



band, whereas in hydrogen the boundary of the most deflected side 

 is distinctly curved and is concave to the undeflected position. The 

 appearance of the deflected phosphorescence is indicated in Fig. 7. 



The result indicated in Fig. 'S, which was also obtained with 

 hydrogen, shows that we have here a mixture of two bands, as indi- 



