Analysis of Atmospheric Air, by means of Nitric Oxide. 265 
the upper orifice of the cylinder is closed, is pressed upon the rim of 
that orifice, so as to make with it an air tight juncture. Froma 
hole in the center of the brass disk, a stout tube of brass proceeds, 
terminating in three cocks, furnished with gallows screws, so as to 
permit of the attachment of three flexible leaden tubes. Of these, 
one communicates with an air pump, another is:attached to a pear 
shaped glass receiver, which (for want of a better name) I shall call 
a volumeter, as it serves conveniently, and accurately, to measure 
gas into precisely equal volumes. 
Vor. XXVIII.—No. 2. 34 
