190 



Professor Sir James Deivar 



[Jan. 20, 



at a certain stage of the increasing pressure of oxyyen, the bulb 

 again becomes a glowing mass of phosphorescence, which wanes 

 and disappears as the normal pressure is reached. This experi- 



■^-■-h. 



ment may be repeated a great many times provided the phos- 

 phorus in the small side tube does not get into active combustion, 

 which can always be avoided by a slight cooling. Such bulbs can be 



