Meteorological, Obfervations. 637 
freedom, and confequently higher, and thus 
gives the bulbous or convex appearance. On 
the contrary, when the quickfilver is falling, 
the fame attraction fubfifling betwixt the par- 
ticles of quickfilver in approximation to the fides 
of the tube and the glafs, thefe will be retarded 
in their defcent; whilft the quickfilver towards 
the center will fink more freely, and the concave, 
irregular, or flat appearance will obtain as the 
tendency to fink is more or lefs prevalent ; for 
the more it is difpofed to fall, the more concave 
will the furface be. But to make this appear- 
ance of the quickfilver propeyiy confpicuous, 
the tube of the barometer fhoulu tz of a certain 
fize, e.g. about half an inch in diameter: be- 
caufe when the diameter of the tube is very 
{mall, the quantity of the quickfilver that will 
be attracted by the fides of the tube, will bear 
fo large a proportion to the whole, as always 
to exhibit a convex appearance ; whilft if the 
tube be very large, the proportion of the quick- 
filver that will be within the attraGion of the 
fides of the tube, will be fo fmall, that the con- 
vexity will be fcarcely difcernible, and it will 
always exhibit a flat or concave furface, as I 
have feen to be the cafe with a barometer of 
nearly an inch diameter. 
j (c) 
