( 779 ) 
Having snade thefe Trials, to alter , by another contiguous 
, iuid than the Air, the Goncave fuperjicies of Water 
and feme Aqueous liquors, I proceeded to try, ^7 he- Exp.viL 
ther a change would not iikewife be made on the 
convex figure of the forface of ^uickfilver included aj^, the 
like flender GlaflTes ; and accordingly, having taken one that 
was much longer, but of the like bore with the former (for 
to make the Trials more uniform , 1 had caufed a long Pipe to 
be by the flame of a Lamp unequally divided into feveral 
fhorc ones) we put into it a final 1 quantity of Quickfilver, 
and having taken notice how the upper fuperficks fwelled in 
the middle above the level of the parts where it touched the 
Glafs, we poured fome Water upon it, and found a manifeft 
ai>d confiderable depreffion of the Surface, though the protu- 
berance were not quite fupprefTed. 
This Phienomenof^ having been for greater fecuricy feveral 
times repeated , I thodaghc fit to try , what varia- 
tion would be made , by the greater or lefler height Esp.Viit 
of the^ water incumbent on the Mercury. And 
fometimes it feem'd^ (hat, when the aqueous Cylinder was 
much longer, the depreffion of the Mercurial furface was fomC" 
whatgreater» But this did not To conftantly happen: Buc 
we often obferv'd, that, though a very litde Water fufficed by 
its contaft to make, in the judgment of the eye, a manifefla-- 
batementof the Protuberance of the Quickfilver, yet it had 
not the fame effeft on that ponderous Fluids that it bad, when^ 
being increafed almofl as high as the length of the Pipe would 
permit, a greater weight of it was incumbent on the Mercury^ 
For then ! manifeftly perceived and fiiew*d to others,tha£ the 
furface of the Quickfilver being deprefs*d almoft to a Level in 
thofe parts of it that were near the iofide of: the Glafsjthere was 
about the middle of thefurfacean elevationof Mercuridnnt' 
ter, thacappeard tobe'rather more than a half Globe, and 
was to the height of its full Semidkmeter^ ralfed above the reft 
of the Mercurial furface, and in that ftate it continued as 
long as I thought fit to let it do To. And lefl: this Tryal 
fliould impofe upon me , I caufed it to be more than once re- 
peated; and, the better to confirm it, I afterwards caufed the 
incumbent Water to be little by little fuckt up, and founds 
as I expefted, that when the Incuniberit water began to be 
