J. Croli— Cause of Mild Polar Climates. 25- 
the Gulf-stream. If the amount of heat conveyed from inter- 
tropical regions into the North Atlantic by means of difference: 
of density resulting from difference of temperature were equal 
to that conveyed by the Gulf-stream, it would follow, as has. 
been proved,* that the Atlantic would be far warmer in tempe- 
rate and arctic than in intertropical regions. Taking the annual 
quantity of heat received from the sun per unit surface at the 
equator as 1,000, the quantities received by the three zones- 
would be respectively as follows:— 
BURT go so os eee SO 
Lorne 8006 sk a Oe 
Temperate zone .. . 157 
Frigid gone .° 454 
_ Assume, then, that as much heat is conveyed from intertrop- 
ical regions into the Atlantic and Arctic seas by this circulation: 
from difference of specific gravity as by the Gulf-stream, and 
assume also that one half of the total heat conveyed by the two- 
Systems of circulation goes to warm the Arctic Ocean, and the 
other half remains in temperate regions, the following would 
then be the relative quantities of heat possessed by the three- 
zones :— 
Atlantic in torrid zone . . . 671 
uy in temperate zone. . 940 
se in frigid zone . . . 766 
; ‘Climate and Time,’ Chap. xi; Phil. Mag., March, 1874. 
es Climate and Time,’ pp. 220-225; Phil. Mag. September and December,- 
15; ‘Nature,’ November 25th, 1875. be 
