Atmospheric Air and Oxygen Gas by Respiration. 251 
Description. 
Fig. 1. The communication with the water gasometer. 
2. A cock so constructed that it might be made to com- 
municate with either of the mercurial gasometers, 
while 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 shewn in 
this drawing, it having been so frequently described in che- 
mical works. 
Manner of conducting the Experiment. 
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- 
tering, &c. by the other, as each would by that means acquire 
a greater degree of dexterity in performing his part, and the 
results would be more uniform. 
The water gasometer being 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 his 
mouth even with the tube A., his nose being secured with 
a steel clip. He made as complete an expiration as possible 
K k 2 
