J. Trowbridge — Doppler Effect in Positive Rays. 247 



slit was a broad one in order to show differences of illumi- 

 nation. 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 mutu- 

 ally repellent transmit movenfents, 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 resnlts a maximum of radiation 

 of greater refrangibility which is separated from the refrangi- 

 bility 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 dis- 

 charge 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 1 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 of 

 the cathode on the glass. These striae can be localized at a 

 definite point by bringing the edge of the disc of the cathode 

 near the wall of the tube ; and we then have a source of positive 

 rays which is analogous to that formed by pushing a glass 

 tube surrounding the anode into the Crookes space.* 



The heating and oxidizing effect from the positive particles 

 of these striae is very marked, especially when the canal region 

 is small, and is much greater than any effect produced by the 

 canal rays in a possible rebounding from the end of the canal 

 region. The photographs of cathode discs exhibit this effect 

 of the positive rays coming from the striae. In fig. 3, No. I is 

 a photogi^h of the back of a cathode made of aluminium 

 formed from as pure clay as could be obtained. The disc was 

 •T5 mm thick and the hard surface formed by the iron rolls was 

 left upon it. The heat from the positive rays coming from 

 the striae caused the occluded gases of the aluminium to form 

 blisters on its surface. No. II represents the back of a cathode 

 formed from the same quality of aluminium as in case I, 

 except that the plate of aluminium was treated with nitric acid to 

 remove any trace of iron coming from the rolls. The surface 

 thus lost its polish and hardness. A very black deposit formed 



*E. Wiedemann, Wied. Ann., lxiii, p. 242, 1897. 



