[ 31 ° ] 
them would increafe by making ufe of fmaller ones. 
Poffibly lefs ones might be ufed without much in- 
convenience. The chief advantage will be, the 
making thefe thermometers more fenfible of the 
changes of heat, than when large cylinders are ufed. 
This will be of fervice when the greateft degree of 
heat or cold continues but a fhort time. 
It is better to ufe plain fpirit of wine, than what 
is tinged, which feems more apt to caufe a foulnefs 
in the tube, and thereby makes the furface of the 
mercury lefs well defined. I am induced to believe 
fo, from obferving, that the portion of fpirits above 
the mercury in the tube fig. 3. which at firfi; was 
ifrongly tinged with cochineal, in fome months be- 
came perfectly colourlefs, the tinging particles being 
depofited in different parts of the tube, and caufing 
a foulnefs there. The colour of the fpirits in the 
cylinder does not appear to be altered. 
r 
The dark-fhaded part in the feveral figures repre- 
ients mercury, the dotted part fpirit of wine. 
} 
XXXIX. 
