XXI.] 



METHOD OF WOKK. 



297 



Some other modifications have been tried, but the first form 

 I have described is that which I have found to answer best, so 

 far as the trials have yet gone. 



A is the tube containing the metal ; 



B, the capillary ; 



c, the connection with the pump. 



FIG. 100. 2nd Form. Spectroscope and lens in position for observing 

 spectrum of capillary. 



In both forms D is the spectroscope, a direct vision being 

 used in the first case. 



E is the lens used for focusing the image of the Geissler tube 

 on the slit in the second case. 



F is the spirit-lamp for heating the retort. 



