for adjujling thermometers. 857 
The firft column of this table is the heat of the air, 
and the fecond is the correction expreffed in 1 oooth 
parts of the diftance between the freezing point and the 
furface of the ice: for example, if the freezing point 
ftands feven inches above the furface of the ice, and the 
heat of the room is 6 2, the point of 3 2 0 fhould be placed 
7 x .00261, or .018 of an inch lower than the obferved 
point. This correction alfo would be made more eafy by 
the help of a diagonal fcale, iimilar to that propofed for 
the boiling point. 
On the precautions necejfary to be obferved in making ob~ 
fervations with thermometers. 
In trying the heat of liquors care fhould be taken 
that the quickfilver in the tube of the thermometer 
be heated to the fame degree as that in the ball; or, if 
this cannot be done conveniently, the obferved heat 
fhould be corrected on that account: but for this we 
refer to the former part, p. 835. 
H. CAVENDISH. 
W. HEBERDEN. 
ALEX r . AUBERT. 
J. A. DE LUC. 
N. MASKELYNE. 
S. HORSLEY. 
J. PLANTA. 
5 P 
Vol. LXVII. 
