2? o Analyfis of the Air. 
like inftrument might be of ufe in any cafe 
where a room was filled with fufFocating va- 
pours, where it might be necefiary to enter 
for a few minutes, in order to remove the 
caufe of them, or to fetch any perfon or 
thing out ; as in the cafe when houfes are 
firft beginning to fire, in the chymifts ela- 
boratories 5 and in many other cafes where 
places were filled with noxious deadly va- 
pours, as in the cafe of ftink-pots thrown 
into fhips, in mines, &c. And might it not 
alfo be ferviceable to Divers > 
But in every apparatus of this kind great 
care muft always be taken, that the infpira- 
tion be as free as polfible, by making large 
paflages and valves to play moft eafily. For 
tho s a man by a peculiar aftion of his mouth 
and tongue may fuck Mercury 22 inches, 
and fome men 27 or 28 high; yet I have 
found by experience, that by the bare in- 
fpiring a&ion of the 'Diaphragm, and di- 
lating Thorax , I could fcarcely raife the 
Mercury 2 inches. At which time the Dia- 
phragm muft ad with a force equal to the 
weight of a Cylinder of Mercury , whofe bafe 
is commenfurate to the area of the Dia- 
phragm, and its height 2 inches, whereby the 
Diaphragm muft at that time fuftain a 
weight 
