and its influence on Climate, 435 



where the calculations are made upon the foregoing* principles, 

 it is stated that the annual intensity of the sun's heat at the 

 equator to that at the poles is as 115 to 14, or as 8 to 1 nearly. 

 If the quantity of heat received from the sun by polar regions 

 were actually as small as the writer of this article states, it would 

 follow that the quantity conveyed by the Gulf-stream from the 

 equatorial regions is equal to about three times all that falls 

 within the arctic circle. 



It is true that a very considerable part of the heat thus trans- 

 ferred by currents from the equator never reaches the arctic 

 regions. But it nevertheless goes to lower the temperature of 

 the equator and raise the temperature of the higher latitudes. 

 Let it be remembered that our calculations refer only to one 

 single current, the Gulf-stream. If we took into account all 

 the currents which flow from the equatorial regions of our globe, 

 we should find that their influence in reducing the difference 

 between the temperature of equatorial and polar regions is 

 enormous. 



A similar function is also performed by aerial currents. The 

 equatorial regions are cooled to a great extent by an aerial cur- 

 rent continually flowing from the polar regions to the equator. 

 And the polar regions at least are warmed by an upper current 

 flowing from the torrid and temperate regions towards the poles. 

 The equator is also cooled to a very great extent by convection. 

 The hot surface of the ground at the equator transfers its heat 

 to the air, and an ascending current is generated which carries 

 the heat upwards and dissipates it into stellar space. 



It is very probable that were it not for the combined effect of 

 all those causes, the difference of temperature between the equa- 

 tor and the poles would amount to at least 200° instead of about 

 80 , as at present. Did the earth possess neither an atmo- 

 sphere nor seas, and were the temperature of each place to de- 

 pend entirely on the direct heat of the sun, the difference of 

 mean annual temperature between the equator and the poles, 

 according to theory, ought to amount to about 200°. 



We may therefore conclude that when the obliquity of the 

 ecliptic was at a maximum, and the pole receiving -^ more 

 heat than at present, the temperature of the poles ought to have 

 been about 14° or 15° warmer than at the present day, provided, 

 of course, that this extra heat ivas employed wholly in raising the 

 temperature. Were the polar regions free from snow and ice, the 

 greater portion of the extra heat would go to raise the tempera- 

 rature. But as those regions are covered with snow and ice, the 

 extra heat would have no effect in raising the temperature, it 

 would simply melt the snow and ice. The ice- covered surface 

 upon which the rays fell could never rise above 32°. At the 



2F2 



