Analyjis of the Air. 249 



lubfide and fall flat, if they were not fre- 

 quently replen ifhed with frefh elaftick air at 

 every infpiration, thro* which the inferior 

 heated vapour and air afcends, and leaves 

 room for the freih air to defcend into the 

 veficles, where the heat of the lungs makes it 

 expand about § part ; which degree of ex- 

 panfion of a temperate air, I found by in- 

 verting a fmall glafs bubble in water, a little 

 warmer than a Thermometer is, by having its 

 ball held fome time in the mouth, which 

 may reafonably be taken for the degree of 

 warmth in the cavity of the lungs. When 

 the bubble was cool, the quantity of water 

 imbibed by it was equal to -$ of the cavity of 

 the whole bubble. 



But when, inflead of thefe frequent recruits 

 of fiefh air, there is infpired an air, fur- 

 charged with acid fumes and vapours, which 

 not only by their acidity contract the exqui- 

 fitely fenfible veficles, but alfo by their groff- 

 nefs much retard the free ingrefs of the air 

 into the veficles, many of which are exceed- 

 ing fmall, fo as not to be viiible without a 

 microfcope ; which fames are alfo continu- 

 ally rebating the elafticity of tha: air; then 

 the air in the veficles will, by Exper. 107, 

 and 108, loie its elafticity very fall; and 



con- 



