1879.] On a New Method of Studying Metallic Vapours. 267 



A is the tube or retort containing the metal experimented on at its 

 lower extremity, and having a platinum wire sealed into it at a distance 

 -of about two inches from the lower end, the other end being drawn 

 out and connected by a mercury joint to an ordinary Geissler tube, 

 which is connected by another mercury joint to the Sprengel pump C. 



Another form of tube which I have used is prepared by inserting 

 two platinum poles into a piece of combustion tubing sealed at one 

 end, and after inserting the metal to be experimented on, drawing out 

 the glass between the platinum to a capillary tube. 



I have also tried inserting the platinum pole at the end of the retort 

 so that the spark passes from the surface of the metal, but this 

 arrangement did not answer at all. 



Some other modifications have been tried, but the first form I have 



