96 Scientific Proceedings, Royal Dublin Society. 
where 
: sin D 
sin/= : 
nA 
and 
m=number of days during which the sun does not set, 
and 
a=59’ 8”, 
But it is evident that 
q:P- 5 
and, therefore, (15) eee i the following expression :— 
na 
Total heat received during the) aD 
om ave Ea Pee ay rer. (ead ae 16 
time that the sun never sets; — 2S Uae: 16) 
bo 
At the Pole itself, since the sun never sets, this expression, summed 
for half a year, gives the total heat received. 
If we calculate from the Equator to the Arctic and Antarctic 
Circles, by equation (13), and from thence to the Poles, by equa- 
tions (12) (with D for A) and (14), we obtain the following 
Table :-— 
TABLE showing the Tota Huat received by various Latitudes from 
the Sun in the course of a Year. 
r 
Latitude. Henaace F See Difference. | 
OF 97°8 97°8 0:0 
10 96°5 96°3 0-2 
20 92°4 91-9 05 
PB Oey 86-7 —_— —_ 
30 85-9 84-7 1107, 
40 77:3 74:9 2-4 
50 66°8 62-9 3:9 
+ 52 30! 61-4 — — 
60 Daal 48-9 68 
t 66 Bye 46-6 = — 
70 46:3 33-4 12:9 
80 41-9 17:0 24:9 
90 40-5 0:0 | 40°5 
The average thickness of ice melted over the entire surface 
of the globe (allowing for the greater areas of the lower 
latitudes), by the annual sun-heat, as deduced from the 
foregoing figures, is exactly 80 feet. 
+ 
* Tropics of Cancer and Capricorn. 
+ Mean Latitude of Ireland. 
{ Arctic and Antarctic Circles 
