sn 3) 
I.. The firft fource of error may 
depend on the inequality in the di- 
ameter of this tube, by which a 
difference of four fub-divifions may 
eafily refult in each partition. 
II. The fecond error may depend 
on the tube not being made rough 
on. the infide, from-which a differ- 
ence of fix fabedivinons mney hap- 
pen. 
Ads. The third may be owing to 
the degree of expanfion of the air 
communicated by the hand in the 
_ time this tube is examined to ob- 
ferve the jength of the column of 
air. ‘This difference may amount 
to four fub-diy ifions. 
“=a The fourth may confift in 
obferving the height of the column 
of water Within the tube, when the 
water within is not on a level with 
the water without ; ; by which an 
, 6 error 
* 
