6 2 Dr. Hunter’s Obfervations on the Heat 
and mu ft therefore be at leafl as warm as London. It is evi- 
dent, that the obfervations from which the mean is taken, 
muft generally contain more of the extremes of heat than of 
cold, as the former happen in the day-time, and the latter in 
the night, in confequence of which they will often efcape 
notice. There is a table conflrudled by Dr. Heberden ex- 
prefting the heat in London for every month in the year, 
from a mean of ten years beginning with 1763, and ending 
with 1772. The mean temperature is given both at 8 A.M. 
and 2 P.M. There is further in the table, a column of the 
mean of the greatefl monthly colds in the night, obferved 
during the fame ten years by Lord Charles Cavendish, in 
Marlborough-ftreet. There will not probably be any great 
error in confidering the heat obferved at 2 P.M. as the greatefl 
daily heat ; and taking a mean btween the greatefl heats of the 
day, and greatefl colds of the night, they give for an 
annual mean,- which is much lower than is commonly fup- 
pofed. At the houfe of George Glenny, Efq. near Brom- 
ley, there is a well feventy-five feet deep, which I found in 
November 49°!. M. de Mairan has given a table of the 
greatefl heats and greatefl colds obferved at Paris for fifty-fix 
years, beginning from 1701; and a mean of them is io° 
above freezing, or 1010°, of Reaumur’s fcale f. The tempe- 
rature of the cave of the Obfervatory where thofe obfervations 
were made, is io°| above freezing, by the fame fcale of Reau- 
mur. There appears not therefore any neceflity for an in- 
ternal heat ; on the contrary, it is matter of demonflration, 
that were there any fource ol heat in the earth which -was not 
equally in the air, the heat of the interior parts ought to be 
: ' K The Table alluded to follows this Paper. 
f Mem, de PAcad. des Sciences, An. 1765, p. 202. 
higher 
