Eg iSO 5] 
this head is f6 much the greater 
when dephlogifticated air is under 
€xamination. 
I have now pointed out twenty 
fources of errors, which may be 
€ommitted in the examination of 
the falubrity of different airs, which 
indeed it would be impoffible to 
commit all in oné and the fame 
trials, but of which fome are con- 
_tinually committed in the methods 
hitherto in’ ufe, and which render 
the accuracy of the te{t as uncertain 
as the experiment itfelf is: how- 
ever, I readily acknowledge, that 
even an accurate philofopher, pro- 
vided with the fame inftruments 
which the Abbé. ules, will find it 
difficult in the beginning to make 
“two experiments with fuch nicety 
“as not to obtain a difference of fome 
few fubdivifionss but he will by a 
Ge 
