C 300 ] 
XXXVIII. A Defcription of fome Thermo- 
meters for particular Ufes. By the Right 
Honourable the Lord Charles Cavendifh,. 
r.p. r.s. 
Read June 30, / g ^HE thermometer (TAB.XI.y 2 g-. ij 
is defigned for fhewing the great- 
eft degree of heat, which happens in any place dur- 
ing the abfence of the obferver. It confifts of a 
cylinder of glafs joined to a tube, and differs from 
common thermometers only in having the top of the 
ftem drawn out into a capillary tube, which enters 
into a glafs ball C, joined on to the ftem at the 
place where it begins to be contracted. The cylin- 
der, and part of the tube, are filled with mercury ; 
the top of which fhews the common degrees of heat 
as ufual. The upper part of the tube above the 
mercury is filled with fpirit of wine, and fome of 
the fame liquor is left in the ball C, fo as to fill it, 
almoft up to the top of the capillary tube. 
Now when the thermometer rifes, the fpirit of 
wine will be driven out of the tube, and will fall 
into the ball C. When the thermometer finks again, 
as the fpirit cannot return back from the ball, the 
top of the tube will remain empty, and the length 
of the empty part will be proportional to the fall of 
the thermometer. Therefore, by means of a proper 
fcale, the top of the fpirit of wine will fhew how 
many degrees it has been higher than when obferved 
which being added to the prefent height, will give 
the greateft degree of heat it has been at.. 
To- 
