tin local Heat. IO jj 
With thefe feven thermometers and the two, before men- 
tioned, in the city, I continued a diary for twenty days, taking 
alfo every morning the temperature of the water in the river; 
but the weather proving cloudy foon after, the thermometers 
hardly varied at all, feven or eight days only excepted. After 
this time I never rectified them but when the appearance of 
the weather gave me reafon to expedl that they would vary confi- 
derably. fee the obfervations that were then taken Tab. IV. ; 
by which it appears, that the cold in the night was generally 
greater in the valley than that on the hill ; but that the varia- 
tions between the thermometers on the ground, and thofe fix 
feet above them, were often as great on the hill as in the 
valley. 
Perceiving now, that a difference of temperature was 
frequently found within three feet from the ground, I refolved 
to try hill nearer; but my thermometers being eighteen 
inches in height could not be applied fo near to the furface of 
the earth as my experiment required ; I therefore conftru&ed 
two others for the particular purpofe ; and by bending down 
the large tube, the bulb or body of the thermometer, to an 
horizontal pofition, while the fmaller tubes remained in a ver- 
tical one, I was enabled to afeertain the different degrees of 
heat from the ground to a fmgle inch. 
At certain times, when the weather was clear, I expofed 
thefe two horizontal thermometers in an open place, fufpend- 
ing one of them, fo as to bring the body of it within an inch 
of the ground, and the other nine inches above it. When 
the variation among the other thermometers was confiderable, 
I found alfo a difference between thefe ; the lower one indi- 
cating fometimes more than two degrees lefs heat than th« 
P 2 upper 
