for adjufting ‘Thermometers . 825 
All three thermometers were found to hand, in gene- 
ral, from 30 to 65 hundredths of a degree higher when 
the ball was immerfed a little way in the water (neglect- 
ing thofe obfervations in which much of the Tides of the 
pot were expofed to the fire) than when it was tried in 
fleam : at a medium they flood higher, which is equal 
to the difference produced by a variation of -—ths of an 
inch in the barometer; fo that the boiling point, adjufted 
at a given height of the barometer, with the ball im- 
merfed a little way in the water, will in general agree 
with that adjufted in fleam, when the barometer is T Uhs 
of an inch higher. 
It muft be obferved, that in all thefe experiments a 
piece of fiat tin plate was laid loofely on the mouth of 
the chimney e, fb as to leave no more paffage for the 
fleam than what was fufficient to prevent the tin plate 
from being lifted up. In trying the thermometers in 
fleam, this is by no means unneceftary; for, if the cover 
of the pot does not fit pretty clofe, the thermometers will 
immediately fink feveral degrees on removing the tin 
plate; but, when their balls are immerfed in the water, 
the removal of the tin plate has no fenfible effebt. 
fleam cannot acquire its full degree of heat; and that when the water boils very 
gently, the air is not eafily intirely expelled from the pot. That the fleam will 
nqt acquire its full degree of heat while any air is left in the pot will appear 
from the next paragraph but one. 
Vol. LXVII. 5 L If 
