p93 
fifty fubdivifions, which, being add- 
éd to the above-mentioned 256, 
will make their number in all. 306 
fubdivifions ; the difference of time - 
between the moment of the mix- 
ture of both airs and the examina- - 
tion will make alfo a confiderable 
difference ; even afew feconds may 
make a fenfible difference, if the 
examination be intended to be 
finifhed in a little while ; but if the 
two airs aiter their mixture are left 
to ftand by themfelves a long while, 
as for inftance 24 hours, the whole 
refult will be uncertain, particularly 
if the degree of goodnefs of dephlo- 
gifticated air is to be examined. 
The remaining fource of error 
confifts in letting up at once all the 
quantity of nitrous air to be em- 
ployed i in the experiment. ‘The un- 
Seay of the refult arifi ing from 
Na _ this 
