522 Prof. J. Trowbridge on the 



was placed at X, no Doppler effect was seen. Wben, 

 however, the cathode was perforated the effect was very 

 evident, and indicated a movement towards X which was 

 equal in amount to that observed in the canal region 

 toward Y. 



Moreover, the photographs showed, when the light was 

 observed at X, a line on each side of the ordinary stationary 

 hydrogen line — my observations were confined to \ = 4861*5. 

 There was evidently a movement toward the anode, and a 

 movement away from it at the cathode. 



When the observations were conducted at Y the same 

 phenomenon was observed — a stationary hydrogen line and 

 a diffuse line separated from the stationary line by a blank 

 space on each side of the stationary line — indicating a 

 movement toward the cathode and away from it. In fig. 2 

 (PL XIV.) a and b are photographs, c is a drawing which 

 represents the effect too feeble to be strongly reproduced from 

 the photographs — effects, however, which are very evident 

 on the negatives a and b. The slit was a broad one to show 

 differences of illumination. The light was strongest at the 

 orifices. 



When the observations were conducted by placing the slit 

 of the spectroscope so that the light at the perforations did 

 not enter the slit — in other words, placing it obliquely to the 

 band of light, the companion of the stationary line which 

 indicated a movement away in each case, from the slit, was 

 not discernible. The effect took place at the orifices. The 

 positive particles jostling through these orifices and mutually 

 repellent transmit movements — like those resulting from 

 elastic particles in impact — in opposite directions, and those 

 driven in the direction of the anode meet others coming 

 toward the cathode. There results a maximum of radiation 

 of greater refrangibility, which is separated from the refran- 

 gibility of the stationary hydrogen line by a less luminous 

 space. 



When glass tubes are inserted in the orifices through 

 which the canal rays pass, and the back of the cathode is 

 protected by glass connected to these tubes and to the wall 

 of the discharge-tube, the canal rays are still obtained. This 

 proves that these rays are produced immediately in front of 

 the cathode — that is, on the side toward the anode — or in the 

 orifices. I incline to the belief, as I have stated, that the 

 jostling in the narrow orifices accounts for the change in 

 refrangibility. 



In all discharge-tubes striae are seen opposite to the edge 



