[ 30i ] • 
To fit this thermometer for a new obfervatfon, it 
is neceffary to fill the upper part of the tube with 
fpirits which may be done, by inclining the inftru- 
ment till the fpirits in the ball C cover the end of 
the capillary tube. For if the cylinder is then heated, 
by applying the hand to it, or by the flame of a 
lamp held at fome diftance, till the fpirits rife to the 
top of the tube and run over into the ball C, and is 
then' fuffered to cool in the fame polition, the tube 
will remain full of fpirits, and the thermometer will 
be fitted for a new experiment. 
The top of the capillary tube is made to ftand 
pretty near to one fide of the ball, and alfo to the top 
of it, that a lefs inclination of the inftrument may 
be fufficient to make the fpirit of wine in the ball 
cover the end of the tube. 
The ball C is joined on as high as pofiible, fo as 
to hide no part of the tube, except that, where the 
bore is contracted. By this means, the top of the 
fpirit of wine begins to appear before the thermo- 
meter has funk one degree. 
It will be convenient to leave fome mercury in 
the ball C, which may be made to cover the end of 
the capillary tube, by inclining the thermometer 
more than what is neceffary to make the fpirit of 
wine cover it. By this means fome mercury may 
be got back into the tube, in cafe any of it fhould 
happen to be driven into the ball by the thermo- 
meter’s being expofed to too great a heat. 
The fcale of degrees at top, which fhews the de- 
fcent of the thermometer from the higheft point .it 
has arrived at, ought not, in firridtnefs, to be the fame 
a i all times of the year; for thofe degrees exceed 
the 
