Anahfts of the Air. 167 
at their nofe, the air contained in them for 
3 minutes, without much inconvenience, 
they heaving and falling very eafiiy by the 
aftion of refpiration. Some fuch like in- 
^ ftrument might be of ufe in any cafe where 
a room was filled with fufFocating vapours, 
where it might be neceffary to enter for 
a few minutes, in order to remove the 
! caufe of them, or to fetch any perfon or 
thing out i as in the cafe when houfes are 
firft beginning to fire, in the chymifts ela- 
I boratoriesi and in many other cafes where 
places were filled with noxious deadly va- 
; pours, as in the cafe of (link pots thrown 
into Ihips, in mines, &c. 
But in every apparatus of this kind great 
, care muft always be taken, that the infpira- 
tion be as free as poflible, by making large 
■ paflages and valves to play moft eafily. For 
tho' a man by a peculiar aftion of his mouth 
and tongue may fuck Mercury 22 inches, 
i and fome men 27 or 28 high 5 yet I have 
I found by experience , that by the bare in- 
I fpiring aftion of the T>iaphragm, and dilate 
ing ThoraXy I could fcarcely raife the Met- 
[ cury 2 inches. At which time the 2 )/^- 
t ^hrdgm muft ad with a force equal to the 
weight 
