[ i66 ] 



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 fub-divifions may hap- 

 pen. 



III. 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 length of the column of 

 air. This difference may amount 

 to four fub-divifions. 



IV. The fourth may confifl 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 



