244 • On the Changes produced in Atmospheric Ah 



are all made to range with each other, so that the quantity of 

 gas inspired and expired could be immediately and exaclly 

 ascertained : to each of the mercurial gasometers a glass tube 

 is fixed, and made to enter a mercurial bath, from which 

 portions of the expired air could at any time be taken for exa- 

 mination. 



By the kindness of our frjend Silvanus Bevan, we are ena-? 

 bled to give an accurate drawing of the apparatus. 



Description. 

 Fig. 1. The communication with the water gasometer. 



'2. A cock so constructed that it mightbemade to corn-? 

 municate with either of the mercurial gasometers, 

 w hile at the same time all connexion with the other 

 was cut off. 

 A. The mouth piece. 

 Fig. 3. to 10. Brass cocks. 



G. 1 . and G. 2. Mercurial gasometers. 

 S.S. Scales graduated to cubic inches. 

 M. Mercurial bath. 

 The large reservoir or water gasometer is not shown ih 

 this drawing, it having been so frequently described in che- 

 mical works. 



Manner of conducting the Expetimejit. 



Our first care was, to be certain that all the parts of our 

 apparatus were perfectly air-tight; and this, from the nature 

 of it, was very easily ascertained ; we agreed that the breath- 

 ing should always be performed by one of us, and the regis-r 

 tering, Sec. by the other, as each would by that means acr 

 quire a greater degree of dexterity in performing his part, 

 and the results would be more uniform. 



The water gasometer beine; filled with common air to a 

 certain mark upon the scale, and the mercurial ones com- 

 pletely empty, the person to breathe, whom we shall uni- 

 formly call the operator, was seated upon a stool, with hi& 

 mouth even with the tube A., his nose being secured with a 

 steel clip. He made as complete an expiration as possible 

 into the open air, then applying his lips to the tube, and 

 keeping his left hand constantly on the cock, fig. l^ and his 



• " right 



