Mr Orange, On certain phenomena of the kathode region. 231 



arrive within close range of the kathodes, they will reverse their 

 paths in such a powerful field that they will gain sufficient impetus 

 to travel in a fairly direct line towards the other kathode. When 

 they have lost so much energy that they fail to reach the high 

 intensity zone at the end of one of their oscillations, they will be 

 dominated much more by the influence of the postulated region 

 of negative charge at the centre of the system, and will be repelled 

 out to form the oblique sheets. 



The ditference between the sheets at the higher and lower 

 pressures can be explained simply thus : At the stage shown in 

 Fig. 1, PI. VII, the kathode rays produced at the interfaces will 

 lose much energy in crossing over (because of the higher gas 

 pressure chiefly). 



Consequently the rays when they start out laterally will be at 

 various distances from the kathode ; that is, they will have lost 

 very different amounts of energy, according to the number of 

 times they have crossed over. There will, however, be a minimum 

 of energy lost corresponding to the case of a single traverse. 

 The sharply defined boundary of the oblique ray sheets can be 

 taken as the expression of this minimum. The other boundary of 

 the rays is at this stage scarcely marked at all, owing to the 

 indefinite range of possible energy losses of the particles in their 

 preliminary movements. Probably, also, the spreading of the rays 

 is conditioned partly by the great range of intensity of field as 

 we cross the narrow Crookes' dark space. 



At lower pressures (e.g. Fig, 5, PI. VII), the particles will lose 

 little energy in their surgings, and so when finally ejected they 

 form a confined sheet. The large dark spaces characteristic of 

 these lower pressures are associated with more uniform fields ; 

 this also will be favourable to the production of confined sheets 

 of rays. 



To test these views of the phenomena a few experiments were 

 made with the two kathodes at different potentials. This was 

 attained by having the lower plate connected as before to the coil 

 terminal, while the upper plate was connected to it through a 

 considerable electrolytic resistance. [The photographs obtained 

 are unfortunately slightly out of focus (except Figs. 1 and 3, 

 PI. IX), but they are clear enough to show the points referred to.] 

 The series, Figs. 1 to 5, PI. IX, shows various combinations of 

 potentials and pressures. In Fig. 1 the upper plate was quite 

 disconnected externally. In the other cases it was connected 

 through various amounts of resistance. 



The first thing noticeable is the inequality of the two Crookes' 

 dark spaces, the upper one varying continuously with the potential 

 and apparently vanishing when the plate is disconnected. This 



VOL, XV. PT. III. 16 



