1898.] on Some New Studies in Cathode and Bontgen Badiations. 585 



consider the condition of affairs inside a focus tube while a discharge 

 is taking place, this List experiment may help us to understand at 

 least one possible reason for the atoms not being projected from the 

 anode at anything like the velocity that they are projected from the 

 cathode. 



Fig. 4 has been prepared to show the probable distribution of posi- 

 tively and negatively electrified atoms 

 in a focus tube while the discharge 

 is taking place. It is larfzely based 

 upon })revious similar illustrations 

 due to Crookes, applied to a tube of a 

 different form. As will be seen, the 

 greater portion of the bulb is filled 

 with positively electrified atoms, as 

 denoted by crosses, while it is only 

 behind the cathode and in the cathode 

 stream itself that any nesatively elec- 

 trified atoms are to be found. That 

 this is at any rate approximately true 

 can be proved by means of exploring 

 poles and in other ways, and it is 

 curious to note that some of the very 

 beautiful photographs published by 

 Lord Armstrong in his recent mono- 

 graph on 'Electric Movements in Air 

 and Water' show that in air at ordinary 

 atmospheric pressure there is a similar 

 tendency for the positive discharge to 

 be much more dispersive than the 



Fig. 4. — Diaij;ramslio\viiicj probable 

 distiibution of positiwiy and 

 nejjjatively charged atoms iu 

 a focus tube. 



ISow assuming that the figure cor- 

 rectly denotes the condition of the 

 atoms inside the tube, it is evident 

 that considering only the contents of 



the tube and disregarding everything outside, the anode is very 

 much in the same condition as the earthed electrode in the pith ball 

 experiment ; being at the same electrical potential as the great bulk 

 of its environment. It is very probably for a similar reason that in 

 a tube of the foj rn illustrated the cathode rays are only given oft' from 

 the concave side of the cathode, the whole environment of the convex 

 side being negatively charged, with the result that the atoms there 

 are in a state of equilibrium. 



Whether this explanation is sufiicient or not — and no doubt there 

 are at work other causes — in any case there is no question that the 

 velocity of the negative stream is very much greater than the velocity 

 of the positive stream. That there is something of the nature of a 

 positive stream, which increases in velocity the higher the exhaustion, 

 can, however, be' shown experimentally. 



