( 42 ) 
Therefore the whole Defcent of the Compound Baro^ 
meter, is to the Afcentof the Mercury in the common 
Barometer, that is,» is to i, as d -f- -j- -f. 
&c. to i* or as — to i 
s • ' a 
of the Series being in Geometrical Progreffion, the 
Sum of them all is Hence we have n =— 1 £ 
s—d s — d 
and n s = d s -f* dn\ that is, i : d s in s : : 
s ss s 
becaufe the Terms 
n s 
: i and i : -y /d, that is, the Diameter of S T 
to the Diameter of H I, as - to i. Q_.E. D. 
n s 
Example I. Putting s — 14 and n — 1, the Va- 
riations in each Barometer will be equal, by taking 
the Diameter of ST to the Diameter of HI as V— : 
14 
that is, as 30 to ry nearly. 
Example II.* If n be put infinite, the Diameter 
of ST will be to the Diameter of HI as V— t0 I > 
s 
or 1 to V that is, as 1 to 3 \ nearly. 
The Bottom of the VefTel V, and the Ends of the 
Tubes, ought to be made rather round than flat for 
their more eafy Motion up and down in the Fluid. 
It will be convenient to have a fmall Bafon fix’d up- 
on the Star, to contain Shot for the more eafy poifing 
the Barometer in the Fluid. 
VI. An 
