FEKMEXT OILS. 



357 



necessary. The funnel, supported by a ring, is lilled with 

 mercury, which runs down the tube to the lower vessel in 

 the form of small cylinders, which are separated from one 



another by spaces occupied by the air continually expanding 

 from the vessel which is to be emptied of air. The air and mercury 

 escape through the spout of the lower vessel. As the exhaustion 

 proceeds, a column of mercury is supported in the vertical tube 



