fargo] 
Thefe three accidental errors, 
though fmall in themfelves, yet may 
amount to fix or more fub-divifions. 
So that all the errors already enu- 
mierated may amount, if they were 
ali committed together, to 260 fub- 
' divifions. 
Befides all the above-mentioned 
fources of errors that may be com- 
mitted, either by indifferent inftru- 
ments, or by want of proper atten- 
tion, there is one which had always 
vexed me in former. and 
which feemed to me, as wer as to 
many others, almoft incorrigible. 
This is the inconitancy in the qua- 
lity of the nitrous air, which is 
_ found fometimes much itronger or 
weaker than at other times, though 
the fame method of apne. it 
3 has been = 
=g _ of 
