[ 3°6 ] 
not affeft the fcale for the common degrees of heat, 
it would however caufe fome error in the degrees on 
the fhortcr leg ; inafmuch as the expanlion of that 
portion of fpirits, which has got up into the longer 
leg, exceeds the expanfion of the mercury, w r hich 
mull; lupply its place. It may be got back at plea- 
l'ure, by expofing the thermometer to fuch a degree 
of cold as will make the fpirit get beyond the bend 
of the fyphon ; for then it will run up along the 
thread of glafs in the fhorter leg till it gets above 
the mercury there. For this purpofe the point of o 
degrees of Fahrenheit’s fcale fhould be near, the bend ; 
by which means, any part of the fpirit of wine may 
be got beyond it by an artificial cold and there will 
be no danger of the whole getting beyond it by any 
natural cold ; in which cafe the air would get up 
. into the ball. 
.The fcale of degrees on the fliorter. leg will, in 
different feafons, be liable to an error of the fame 
kind as that, which was explained in the firff-men- 
tionecl thermometer ; but in this it will be lefs con- 
fiderable, as the fpace between the two feales is filled 
with mercury, whofe expanfion is about fix times 
lefs than that of fpirit of wine. 
In the thermometer, which I have, the bore of 
the tube is about 0.054 inches; and one inch of it 
contains eight grains of mercury, and anfwers to: 
feven degrees of Fahrenheit’s fcale. The drops of 
mercury, which fall into the ball A, anfwer to 
about one eighth of a degree. 
If inflruments of the nature of thofe above de- 
ferified, were to be ufed for finding the temper. of 
the 
