76 ME U O IK S of the 
river o[ Gon, which contains albrt of oifter; it is very rare, and 
its ihell powdered is efteemed a good medicine. 
Tbe proportional Heat of the Sun in all Latitudes, "joith the 
Method of ColleBing the Same-y by Mr. Edm. Halley. Phil. 
Tranf. N° 203. p. 878. 
IF we confider the action of the fnn as the only caufe of the 
heat of the weather, Mr. Halley thinks, that under the pole 
the Iblftitial day may be as hot as it is under the equinoftial, 
when the fun comes vertical, or over the Zenith j and that for 
this realbn, that during the 24 hours of that day under the pole, 
the fun's rays are inclined to the horizon in an angle of 2 3 1 de- 
grees, and under the equino£lial, tho' he come vertical, yet he 
mines no longer than 12 hours, and is again 12 hours abfent; 
and that for 5 hours 8 minutes of thefe 12 hours he is not h much 
elevated as under the pole; fo that he is not 9 of the U'hole 24 
hours higher than he is there, and 1 5 hours lower : Now, the 
fimple a£lion of the fun is, as all other impulfes or ftrokes, more 
or leis forcible, according to the fine of the angle of incidence, or 
to the perpendicular ht fall on the plane ; whence the vertical 
ray, being that of the greatcft heat, being put radius, the force 
of the fun on the horizontal furface of the earth will be to that, 
as the fine of the fun's altitude at any other time : This being al- 
lowed, it will then follow, that the time of the continuance of 
the fun's fhining being taken for a bafis, and the fines of the fun's 
altitudes ereficd thereon, as perpendiculars, and a curve being drawn 
thro' the extremities of thole perpendiculars, the area compre- 
hended will be proportional to the colledlion of the heat of all 
the rays of the fun in that fpace of time ; hence it will follow, 
that under the pole, the colleflion of all the heat of a tropical 
day is proportional to a redangle of the fine of 23 j deg. into 
24 hours, or the circumference of a circle j that is, the fine of 
251 deg. being nearly 4 tenths of radius- as fo into I2 hours • 
or the polar heat is equal to that of the lun continuing 12 hours 
above the horizon, at the height of 5 3 deg. than which the fun 
is not five hours more elevated, under the equincftial: But that 
this may he better underftood in Fig. 4. Plate II. the area ZG 
HH is equal to the area of all the fines of the fun's altitude 
under the equinodlial, ere£ted on the refpe6tive hours from lun- 
rifin^ to the Zenith j and the area vj H H v^" i^^^ in ^^^ ^'^^^^ Pro- 
portion to the heat for the lame 6 hours under the pole on the 
tropical day 5 and H H Q^ is proportional to the collected heat 
of 1 2 hours or half a day under the pole 5 which Ipace O H H Q^ 
IS 
