Liquefaction of Gases. 201 



internal diameter, and serving to receive the liquid oxygen 

 under atmospheric pressure. The tube e is surrounded by two 



others, of greater and greater diameter, and hermetically closed 

 above with a brass plate g. The whole apparatus is her- 

 metically placed in a larger glass cylinder, with calcium 

 chloride at the bottom, serving to dry the enclosed air. The 

 top of the tube / is connected with the manometer b and the 

 iron bottle c, containing absolutely pure and dry hydrogen, 

 under a pressure of 150 atm. ; the cock I serves to let the 

 hydrogen out of the tube f thus producing the expansion ; 

 through the upper end of the tube f, which is closed with the 

 screw m, a thermoelectric junction may be introduced, if it 

 be required to measure the temperature of the hydrogen at 



