248 J. Trowbridge — Doppler Effect in Positive Bays. 



under the effect of the positive rays of the striae, which was 

 probably carbon from the aluminium. In III the cathode was 

 formed from ordinary commercial aluminium l*5 mm thick. It 

 represents the blackening which results from long running of 



Fig. 3. 



II 



ill 



IV 



Fig. 4. 



the] discharge. At increased exhaustions and during this 

 long use of the tube the striae shift their position, and the back 

 of the cathode shows a general discoloration. No. IV repre- 



