( « >9 ) 
annexed be divided into Parts by the defcent of the 
Mercury, at every ten Foot, in both the pendent Baro- 
meters, which I conceive may be fo choien as to make 
die Divifions very diftindt and fenfible. Thefe thus 
prepared, when it is defired to take the Level of two di* 
ftant Places, let one of them be placed in the lower 
Place, at a time when the Mercury has the fame height 
as when they were fir ft inverted and graduated ; and 
let the other be carried to the higher Place, where it 
will be found to ftand at that divifion which anfwers the 
elevation cf that Place above the other, the which had 
before been found by meafure in afcending the Monu- 
ment". Thus may 90 Foot afcent, which makes bur- 
one tenth of an Inch of Mercury , be reprefented by two 
or three Inches, or a (pace capable of being divided 
into 90 Parts : Whereas, if the diftance of the two 
Places be 20 Miles, a minute of a Degree is equal to 
above 30 Foot s and by the ufual Sights, whether 
Telefcope or other wife, of your Water Levels, I fear ic 
will be very hard to convey a true Level without a* 
greater Error than one Minute in the whole. This 
Propofal 1 humbly fubmit to the Examination of this: 
Honourable Society. 
X. Ob - 
