836 Report of the Committee 
that air will be affedted by the fleam of the liquor, and 
the fire by which it is heated, it will commonly be of a 
very different heat from the reft of the air of the room 
in which the experiment is made ; but as no great nicety 
is required in eftimating the heat of the quickfilver in 
the tube, infomuch that a miftake of 25 0 therein will 
caufe an error of only half a degree in the correction, 
when the number of degrees in that part of the tube 
which is not immerfed in the liquor is not more than 
220°, it will commonly be not difficult to guefs at 
the heat of the quickfilver in the tube as near as is re- 
quired'"' 7 . But if the obferver is defirous of more accu- 
racy^. 
was laid between the fand and it. After it had remained a fufficient time in 
this fituation, the divifion which the quicksilver flood at was obferved. The 
piece of wood was then, removed, and the end of the tube laid in the fane!, 
which was heaped over it fo that about half an inch of the column of quick- 
filver was intirely furrounded by the hot fand, and muff therefore be heated to 
nearly the fame degree as it. The quickfilver in the tube rofe very little higher, 
than before, and feemingly not more than might be owing to the expanfion of 
the half inch of quickfilver which was furrounded by the fand; fo that itfhould 
feem, that heating one end of the. column of quickfilver does not communicate 
much heat to the reft of the column; and confequently, that, when the ball of 
a thermometer is immerfed in hot liquor, the quickfilver in the tube will not be. 
much hotter than the furrounding. air. 
(i) The better to enable the reader to guefs at the heat of the quickfilver in 
the tube, in cafes of this kind, we. tried how much the quickfilver in the above- 
mentioned tube, without a ball, would be heated when held over a vefiel of 
boiling water. It is true, that thefe experiments cannot be of any great fervice 
towards this purpofe, as the tubes will be very differently heated, according to 
the 
