[t reo’ J 
not fufficiently fimple. They are, therefore, difficult to execute, 
hard to keep in repair, and confequently too expenfive to ferve 
the advancement of knowledge as extenfively as might be wifhed, 
I might alfo add that the difficulty of adjufting them correly 
renders the obfervations more uncertain than they might .be’ 
were the inftrument lefs complex. 
As a {mall attempt towards the improvement of this inftru- 
ment, I beg leave to offer to the Academy the following defcrip- 
tion of a portable barometer of more fimple conftruction. 
Tue beft barometers of the modern conftruction are furnifhed 
with floating gages, in order to afcertain the proper height of 
the mercury in the bafon, from the furface of which the fcale 
commences. In the barometer now offered to the Academy this 
end is more fimply accomplifhed by making a hole in the 
fide of the bafon at a proper height, fo that it cannot at any 
time, when hanging perpendicular, contain more mercury than 
will exaétly rife to the ftandard level. This will be beft under- 
{tood by the general defcription, Fig. 1. 
Tue body of the barometer confifts of an upper box a, and a 
_ lower 4. In the upper box is the bafon of mercury f, in which 
the tube ¢ with its attached thermometer are immerfed. The 
bafon communicates with a bag e (which hangs in the lower 
box, and is glued clofely to the upper) by a long perfora- 
tion g in the fide and parallel to it, which is opened and fhut 
at pleafure by a ftop cock 4, with a hole & in the direction of 
its axis reaching as far as the perforation in the fide of the box, 
and 
