{262 79 
with the fame common and nitrous 
air, the Shel of the refult does 
not amount to of the bulk of 
both airs. 
The. different degrees of. falu- 
brity will be found in general to lie 
between I103-and 1993 at leait, I 
found it almott always to be within 
' thefe two extremes: that is to fay, 
that of the -bulk of the two airs 
the remaining column will be found 
to occupy between 103 and tog 
fubdivifions.. The magnifier ap- 
plied to the brafs tube (D, Fig. 1.) 
afflifts greatly the accuracy et the 
obfervation. 
-This fimple method SaGantly 
fhewea me. all the variations in the 
conititution of the atmofphere, in 
3 = to its. fitnefs for refpiration, 
whic a ac ciicover By any otRer 
ie a 
200 
