{ 4 l ) 
of fuclia Magnitude of HS will exceed the Length of 
an equal Magnitude of Quickfilver in the larger 
Tube X, as much as the Square of the Diameter at 
X exceeds the Square of the Diameter at H (the 
Lengths of equal Cylinders being reciprocal to their 
Bafes). That is, the perpendicular Defcent of the 
compound Barometer will be to v, the perpendicular 
Afcent of the Mercury in the common Barometer, as 
d to i (fuppoling this the Ratio of the Bafes) and 
confequently will be equal to d v. 
But by this Defcent, the Diftance P W between the 
Surface of the ftagnant Quickfilver and the Top of 
the Fluid will be augmented by a Column, whofe 
Height is d v, the Defcent of the Compound Baro- 
meter ; and confequently the Weight of the whole 
Column of the Fluid preffing on the lower Surface of 
the Quickfilver (to which the Height X is partly 
owing) will beencreafed by a Column of that Length, 
and this Increafe, would produce a fecond Afcent of 
the Mercury at X equal to itfelf, namely d v, were 
the Fluid as heavy as Quickfilver ; but fince it is fup- 
pofed to be lighter in the Ratio of s to i, the Afcent 
of the Mercury on this Account will only be-^-^ 
But now, as in the former Cafe, when the Afcent 
of the Mercury was v, the Defcent of the Compound 
Barometer was fliown to be dv t fo here the Afcent 
d c v 
of the Mercury being - — > the Defcent of the Com- 
s 
pound Barometer will be - ~ and the next Defcent 
d d dv 
s s 
and the next 
d*‘ v 
and fo on to Infinity 
F There 
