[ moa} | 
Amonc other advantages of the prefent barometer it feems' 
to poflefs the following: There is no wafte of mercury, and 
the farface in. the bafon is. more accurately determined than 
can be. done by floating gages; as errors may. arife in ‘the 
adjuftment of them from parallax, from friGtion, and from their 
not diftinguifhing accurately very {mall variations in the altitude 
of the furface, as the prefent. barometer does. 
Tue following experiments nr that oar’ grains ‘of mercury 
cannot be added to the quantity which reaches to the ftandard 
height in the. bafon without overflowing. And yet four grains 
of mercury or more diffufed over a circular furface an inch in 
diameter (about the diameter of the bafon I. made the experi- 
ment upon) would hardly raife it fenfibly, the bulk is fo {mall 
iN proportion to the. weight. 
ete 
cri 
I susPENDED (fee Fig. 2) at the arm of a balance, and coun- 
terpoifed the barometer. I took out the ftop-cock with the 
hole at right angles which communicates with the perforation 
in the fide, and conduéts the overflowing mercury into the bag, 
and put in its place one with a hole of equal diameter in ‘the 
direction of the axis only, and opening without the box, ‘fo 
that the mercury, which was more than enough to fill the bafon 
to, the ftandard height, fhould (through this place) flow out of 
the bafon into a veffel not at all conne@ted with it I balanced 
the barometer accurately when the bafon was filled as‘ high as 
it could contain mercury, hanging freely and in a perpendicular 
direction. I then frequently inclined the bar®meter, and through 
‘i the 
