

Avalyfis of the Air. 



167 



at their nofc, the air contained in them for 

 3 minutes, without much inconvenience, 

 they heaving and falling very eafily by the 

 action of refpiration. Some fuch like in- 

 ftrument might be of ufe in any cafe where 

 a room was filled with fuffbcating vapours, 

 where it might be neceflary to enter for 

 a few minutes, in order to remove the 

 caufe of them, or to fetch any perfon or 

 thing out s as in the cafe when houfes are 

 firft beginning to fire, in the chymifts ela- 

 boratoriesj and in many other cafes where 

 places were filled with noxious deadly va- 

 pours, as in the cafe of ftink pots thrown 

 into mips, in mines, &c. 



But in every apparatus of this kind great 

 care mult always be taken, that the infpira- 

 tion be as free as poflible, 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 in- 

 fpiring aftion of the 'Diaphragm, and dilat- 

 ing Thorax, I could fcarcely raife the Mer- 

 cury 2 inches. At which time the 'Dia- 

 phragm muft ad with a force equal to the 



weight 



it 







I 



