HEA fF. 
ences are as the fines of the altitude inta, or multiplied by, 
the fines of declination. 
general idea may 
‘be conceived of the fum of all the aGtions of the fun in the 
rom g 
trical certainty. The heat of the fun, for any {mall por- 
‘tion of time, is a reCtangle, contained under the 
fine of the angle of incidence 
that time. — 
Many objections have 
theory of Dr. Halley: f 
the fun’s heat i 
angles of incidence, but in the duplicate ratio of thefe fines; 
f the impulfe of fluids. (S 
Dr. Halley himfelf was well apprifed, that many 
other circumitances, befides the direé& iis of the fun’s 
Tays, contributed’ to ry or diminifh the effe@ of this 
and the heat refulting from it i 
therefore, no calculation, 
of the ray producing heat at 
continue to increafe, though the fu owards the 
fouth: and this is the reafon why July is hotter than June, 
although the fun has withdrawn from the ummer tropic ; 
as we find it is generally hotter at three in the afternoon, 
hen the fun has declined towards the weft, that at noon, 
son the meridi As long as the heating par- 
ticlés, which are conttantly received, 
therefore our heat muit 
there are 1co 
day, whilft the f 
ore 
heat received in the day-time than. thot. that fly off in 
: " in 
f z weaker, mo . 
night time than-thofe we receive 
time to’be heated again; 1 re, we find Janua 
for the moft part colder than December, although the (in 
has wn'from the winter tropi¢, and begins to emit 
dus rays more perpendicularly upon us. aes = 
itis well’known that the fun is farther from the earth 
ee number of the fun’s rays falling on CD, «. gr: I 
in fummer than in winter, which induce 
» fund of heat, equal 
n 
: creafe 
articles that excit® - 
in 
c to 
already ftated ; and it will appear (by Plate XVI. Affronomy, 
the 21ft of June; but on the 22d of D 
eat at noon at the winter folftice, i 
iy nearly as 100 to 28; for, the meridian height of. | 
' the fun, at the fummer folftice, being there 61° 19’, and his 
height at the winter folftice 14° 21', the fines of thefe angles 
are 8772858 and 2478445 refpedtively. . : 
Monf. de Mairan, allowing for the auie: 
the fummer heat, ftates the proportion of fummer-heat to 
the proportion of 2 to 1, and that ariling from the gr ; 
length of days as 4 to 1; and, therefore, the heat of oe, 
is to that of winter as 72 to 1. But there are fome other 
proportion of 72 to 1 to that of 66 to 1. 
“However, M : 
to degrécs, to which 6€ af 
i m wh - winter, and thus he ad- 
; of M. Amonton% 
es ss Ber ee A 
calculations of this kind muft be in a confi ee 
ious, on account ateral circumitances,, that of 
tribute to increafe or diminifh the effe& of the fun’s rays #8 
wn in this article, and more fully uice 
e a ee 
Fahrenheit’s thermometer ; but we are apt to reckon hae ae 
cold at 24°, and it Fae coldith to 40° and See 
