II. RESEARCH. 



573 



which a thermometer is placed. The gas pipette is connected with the gas 

 holder by a paraffin joint at f. The arrangements for working this pipette 

 are similar to those in the case of the gas-holder. 



In order to estimate the changes in bulk which the electrized gas under- 

 went in the various experiments hereafter described, the measuring apparatus 

 was employed, of which a drawing is given, Eig. 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 Regnault'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, 6, containing an amount of mercury rather more 

 than sufficient to fill the cylinder a. In the iron tube connecting the cylinder 

 and the reservoir is intercalated a stopcock c, by which the connexion 



FIG. 3. 



