246 J. Trowbridge — Dojppler Effect in Positive Bays. 



rose-colored cones of light, the apex of one directed to the 

 anode and the apex of the other toward the canal region. The 

 body of the luminous cone in the space between the anode and 

 the cathode is, so to speak, a solid, while that in the canal 

 region, or back of the cathode, is made up of a collection of 

 tubes which in a short region come together at the apex of the 

 cone, and in a more extended region spread out in a diffused 

 manner. When the cathode is unperforated the rosy glow, 

 which in the case of hydrogen characterizes the canal rays, 

 emanates from the central portion of the aluminium cathode ; 

 it is no longer conical in form, or rather resembles a frustrum 

 of a cone, the base directed to the anode. It does not extend 

 as far toward the anode as the conical discharge from the per- 

 forated cathode and is not so bright. With the unperforated 

 cathode and the slit placed at X, no Doppler effect was seen. 

 When, however, the cathode was perforated the effect was very 



Fig. 2. 



. j 



evident and indicated a movement toward X which was equal in 

 amount to that observed in the canal region toward Y. More- 

 over, 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, a and b are 

 photographs, o is a drawing which represents effects too feeble 

 to be strongly reproduced from the photographs — effects, how- 

 ever, which are very evident on the negatives a and b. The 



