Analyfis of the Air. 267 



at their nofe, the air contained in them for 

 3 minutes, without much inconvenience, 

 they heaving and falling very eaftly by the 

 a&ion 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 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- 

 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. 



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 

 paflages and valves to play moft eafily. For 

 tho' a man by a peculiar aftion of his mouth 

 and tongue may fuck Mercury zz inches, 

 and fome men 27 or 28 high 5 yet I have 

 found by experience , that by the bare in* 

 fpiring aftion of 'the "Diaphragm, and dilate 

 ing Thorax, I could fcarcely raife the Mer- 

 cury 2 inches. At which time the 'Dia- 

 phragm muft aft with a force equal to the 



weight 



