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Description of an Apparatus for 



through which a copper rod slides so as to reach above the level 

 of the air-pump plate. The end of the rod supports a small hor- 

 izontal platform of sheet brass, which receives four upright screws. 



These, by pressure on brass bars extending from one to the other, 

 are competent to secure upon the platform a parallelopiped of 

 charcoal. Upon the air-pump plate a glass bell is supported, and 



