the Royal Society’s Injlruments . 381 
befl artifts, differ from one another bv not lels than 2- 0 : 
owing partly to a difference in the height of the barome- 
ter at which they were adjufted, and partly to the quick- 
filver in the tube being more heated in the method ufed 
by fome perfons than in that ufed by others. It is very 
much to be wifhed, therefore, that fome means were 
ufed to eftablifh an uniform method of proceeding; and 
there are none which feem more proper, or more likely 
to be effectual, than that the Royal Society fhould take it 
into confideration, and recommend that method of pro- 
ceeding which fhall appear to them to be moft expe- 
dient. 
Of the barometer , rain-gage , wind, and hygrometer . 
THE barometer is of the cittern kind, and the height 
of the quickfilver is eftimated by the top of its convex 
furface, and not by the edge where it touches the glafs, 
the index being properly adapted for that purpofe. This 
manner of obferving appears to me more accurate than 
the other; becaufe if the quickfilver fhould adhere lefs 
to the tube, or be lefs convex at one time than another, 
the edge will, in all probability, be more attested by this 
inequality than the furface. I prefer the cittern to the 
fyphon barometer, becaufe both the trouble of obferving 
and error of obfervation are lefs ; as in the latter we are 
liable to an error in obferving both legs. Moreover, the 
quickfilver can hardly fail of fettling truer in the former 
E e e 2 than 
