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It has been frequently triecb that if a Gallon of 
Air be .contained in a Bladder, and by means of a 
Blow-pipe infpired and expired into the Lungs of a 
Man, without having any Communication with the 
external Air ; in the Space of a Minute, or little more, 
it becomes heated, and unfit for Refpirationj and 
without the Addition of frefh Air, the Perfon would 
fpeedily be fuffocated. The Diving-bell is another 
Inflance of the fame kind, where a conftant Supply 
of frefh Air muft be had, to keep out the Water, and 
refrefh the People included. 
4 Although Air is abfolutely neceffary to our Exig- 
ence, and Neceflity conflrains us inevitably to breathe 
therein, it may be made a Vehicle of moft malignant 
Poifons, as the famous Grotto del Cani in Italy-, 
poifoning Air by Charcoal, Air impregnated with 
the Fumes of fermenting vegetable Liquors, flagnant 
Air, either alone or mixed with Water, foon be- 
comes pernicious, and very offenfive } as in Wells 
dug for Supply of Water, and difufed for fome time.; 
alfo in the Wells, and in the Holds of Ships, where 
what is ufually called the Bulge-water, if the Ship is 
tight, and the Water not pumped out often, it foon 
becomes fo extremely poifonous, as frequently to 
fuffocate thofe Seamen, who, as the Pumps are fub- 
jed to be clogged with Filth, venture down to 
cleanfe them ; and alfo to affed Perfons at a Diflance 
with violent Head-achs, cold Sweats, and frequent 
Vomitings, which continue more or lefs, in Pro- 
portion to the Diflance from the Well of the Ship 
when the Injury was received, and the Degree of 
Putrefadion in the Water and Air. 
The 
