I. RESEARCH. 



497 



went in the various experiments hereafter described, the measuring apparatus 

 was employed, of which a drawing is given, Fig. 4. In this apparatus, 

 which I shall term the aspirator, the volumes of gas at C. and 760 millims. 

 pressure is ascertained by determining the pressure which it is necessary to 

 put upon the gas in order to cause it to occupy a known space at a known 

 temperature. This is the principle of Kegnault's apparatus for gas analysis, 

 and also of Frankland's apparatus. 



The pipette was placed on a table, being separated from the aspirator by 

 an interval of about 8 or 10 inches. In this interval the experiment to which 

 the electrized gas was submitted was made. 



The aspirator consists of a cylinder of strong glass a, connected by an iron 

 tube with an iron reservoir, b, containing an amount of mercury rather more 



fl F/c . 4 . 



39508. 



