420 Scientific Proceedings, Royal Dublin Society. 
The corresponding results for the Southern Hemisphere are— 
Sun-heat. Mean Temperature. Latitude. 
55:7 feet of ice, eh Oso wa f : 2) GUS 
66:84 «: AGB ie es ; 4050 
73, Ay (ss ; , Beg 
B59 © Ht HeGraveeke > wa0 
92-4, TATA ieee é . 20 
965, Gest e : AG 
973, hie (SO sta ar ee AD 
From these data we obtain, by Rossetti’s law,— 
Latitude. a. 
Cyne tae. . 540° F, 
Oya lee . 402 ,, 
4 
Gdyag t= . 603 ,, 
Cyan: . BLO, 
20 
6)45 75 ,, 
1 
(6.) oe . 903 ,, 
Mean, . . 62:217°9 F. 
From this it follows that the mean “sky-temperature,’ which 
controls the radiation of heat from the surface of the earth, is 
higher in the Southern Hemisphere than in the Northern ; so 
that the Southern Hemisphere retains more of the heat received 
from the sun than the Northern Hemisphere* does. 
The sky-temperature of Frolich corresponds with the tempera- 
ture zenithale of Pouillet, which is the exact equivalent of the 
joint action of the atmosphere and of space upon the ther- 
mometer. 
Both Pouillet and Frolich have attempted to separate the vari- 
able effect of the atmosphere from the constant effect of space, and 
Pouillet finds for the temperature of space (— 142° C)= — 223°6 F 
Frolich finds for the temperature of space ( Weltrawms-temperatur), 
by St. Petersburgh observations, 17th August and 23rd October, 
- 131°C and - 127°C, the mean of which gives — 202°2° F. 
* This is due to greater water-surface, and consequently greater amount of aqueous 
vapour in the air. 
