196 



THE FLOATING-MATTER OF THE AIR. 



excluded. A small gas flame is carefully applied at o. 

 The liquid within the narrow tube vaporizes, and the 

 vapour drives the liquid to some distance right and left 

 from the place of heating. In the absence of the liquid 

 the fine tube reddens, fuses, and is hermetically sealed. 



Fig. 20. 



The aspect of the bulb after it has been thus charged is 

 shown at c, fig. 20. 



By this method, on the 20th of February sixteen 

 bulbs were charged with infusions of old Heathfield hay 

 and of a hard wiry hay from Guildford, not old. They 

 were divided into four groups, four bulbs in a group. 



