724 Co/. roy’s Experiments for 
Some months fpent in Scotland in the dimmer of 
1774, afforded opportunities of makihg barometrical ob- 
fervations on hills of various heights, from three or four 
hundred, to upwards of three tlioufand feet, as hath been 
exhibited in the preceding lift. That feafon was re- 
markably cold and wet; wherefore, in thel'e obfervations, 
the mean temperature of the air in the fliade was com- 
monly about 55 0 . The hotted never exceeded 63° in 
the plain; and the coldeft, namely thofe on the highelt 
mountains, were generally from 43 0 to 48°. 
From the defect found in the refults of thefe obferva- 
tions, which, with refpect to temperature, correfpond to 
the mean and hotted of thofe made at Sun-riling on Sa- 
leve, and without any exception whatever, I could ealily 
difcover, either that a much greater equation than what 
the rule directed, mud be applied for each degree of heat 
above the zero of the fcale; or, that the zero itfelf would 
fall con fiderably dower than 39°74, where Mr. de luc's 
formula, adapted to Englifh meafures, hath fixed it. 
This fil'd dep towards a correction of the rule, naturally 
pointed out the fecond thing to be aimed at, namely, the 
obtaining of a fufficient number of cold obfervations, 
near the zero, and as far as poffible below it, that the 
equation might difappear entirely, and even come to be 
applied with the contrary fign. Of this kind the winter 
leafons 
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