684 



PROCEEDINGS OF THE AMERICAN ACADEMY. 



the same diameter as the capillary, and were inserted in the capillaries 

 until the distance between the ends of the terminals in the capillaries 

 varied from one centimeter to two millimeters. 



The capillaries were made of lead glass ; of German glass which did 

 not contain an appreciable amount of lead ; and of quartz. 



When an electric discharge occurs near a luted joint or surface a 

 species of what may perhaps be termed electric distilling takes place. 

 If silicate of soda is the luting agent, the vessel containing the rarefied 

 gas becomes coated with a white film which shows the soda reaction ; if 

 a preparation of gums or shellac is used an organic film is obtained. 



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By the use of long capillaries in which the discharging metallic points 

 are several inches from the points of luting this distilling action can be 

 entirely avoided. It is therefore not necessary to use platinum for closing 

 the ends of- the capillaries in order to exhaust the latter. Quartz capil- 

 laries can be used without fear of introducing impurities from the luting 

 agents, if long terminals are employed with the luting points at a dis- 

 tance from the discharge points. 



In the use of capillaries with metallic terminals almost in contact with 

 the walls of the containing vessels there must necessarily be spectra, one 

 would suppose, arising from the substances of these walls and a combina- 

 tion of these substances with the rarefied gases. It is also possible that 



