J. Trowbridge — Doppler Effect in Positive Rays. 249 



sents the front of the cathode of fig. 3. The center is bright, 

 while the edges are discolored. Goldstein has noticed that 

 positive rays remove deposits. 



Fig. 4 is a photograph of the canal rajs which shows also 

 the luminosity on the back of the cathode produced mainly by 

 the strige. 



The order of spectrum produced by the Rowland grating; 

 gave an interval of '9 millimeter to six Angstrom units. The 

 approximate interval between the Doppler effect on both sides 

 of the stationary hydrogen line 4861'5 was three Angstrom 

 units ; the difference of potential between the anode and the 

 cathode varied from 6000 volts to 10,000. The current ran 

 from 10 milliamperes to 5. A storage battery of 10,000 cells 

 was emploved. The internal diameter of the discharge tubes 

 was 3 cm . the distance between X and C, fig. 1, was 6 cm . The 

 distance between C and Y varied from 4 cm to 10. 



Jefferson Physical Laboratory, 



Harvard University, Cambridge, Mass. 



