17 o Analysis of the Air. 



fuch-like inftrument might be of ufe in any 

 cafe, where a room was filled with fuffoea- 

 ting vapours, where it might be necelTary 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 ; and in many other cafes, where 

 places were filled with noxious deadly va- 

 pours, as in the cafe of ftink-pots thrown 

 into (hips, 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 poffible, by making large 

 paffages and valves to play moft eafily. For 

 tho' a man by a peculiar action 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 infpi- 

 ring action of the Diaphragm, and dilating 

 c Thorax y I could fcarcely raife the Mercury 

 two inches. At which time the Diaphragm 

 muft act with a force equal to the weigh c of 

 a Cylinder of Mercury, whofe bafe is com- 

 menfurate to the area of the Diaphragm, and 

 its height two inches, whereby the Dia- 

 phragm muft at that time fuftain a weight 



- equal 



