ADMIRABLE CHEMICAL INVESTIGATION. 207 



several large glass flasks, which were first en- 

 tirely exhausted of air by means of a very 

 powerful and perfect air-pump, the vacuum 

 being properly tested before the vessels were 

 used. On arriving at the proper locality, the 

 mouths of these vessels were opened, the air 

 immediately rushed in and filled them ; they 

 were then closed and conveyed to the labora- 

 tory, and the analysis of the air was commenced. 

 One of these flasks was connected with the tube 

 of the analysing apparatus ; and at the opposite 

 end of the apparatus was attached a similar 

 flask, only perfectly vacuous. By this means 

 it was intended that the air of the first flask 

 should be drawn through the apparatus, into 

 the second. The flasks and whole apparatus 

 were now carefully weighed. The stopcock of 

 the vacuous flask, and that of the one filled with 

 air, were then opened, thus causing the air from 

 the one to pass on to the other, through several 

 liquids, in which its watery vapour and other 

 impurities were arrested, and finally over metallic 

 copper, finely powdered, and heated to redness, 

 a substance which has the remarkable property 

 of instantly arresting and absorbing every par- 

 ticle of oxygen from the air as it is passing 

 over it. Thus at length nitrogen only re- 

 mained, and passed on into the flask. After 

 the process was completed the apparatus was 



