86 Mr. J. Croll on Ocean-currents in relation to 



means of the upper currents of the trades ; for the heat conveyed 

 by conduction along the solid crust, if any, can have no sensible 

 effect on climate. But these currents, as we have just seen, are 

 ill adapted for conveying heat. 



The surface of the ground at the equator becomes intensely 

 heated by the sun's rays. This causes it to radiate off its heat 

 more rapidly into space than a surface of water heated under the 

 same conditions. Again, the air in contact with the hot ground 

 becomes also more rapidly heated than in contact with water, 

 and consequently the ascending current of air carries off a greater 

 amount of heat. But were the heat thus carried away transferred 

 by means of the upper currents to high latitudes and there 

 employed to warm the earth, then it might to a considerable 

 extent compensate for the absence of ocean-currents, and in 

 this case land at the equator might be nearly as well adapted 

 as water for raising the temperature of the whole earth. But 

 such is not the case ; for the heat carried up by the ascending 

 current at the equator is not employed in warming the earth, 

 but is thrown off into the cold stellar space above. This ascend- 

 ing current, instead of being employed in warming the globe, is 

 in reality one of the most effectual means that the earth has of 

 getting quit of the heat received from the sun, and of thus 

 maintaining a much lower temperature than it would otherwise 

 possess. It is in the equatorial regions that the earth loses as 

 well as gains the greater part of its heat ; so that, of all places, 

 here ought to be placed the substance best adapted for pre- 

 venting the dissipation of the earth's heat into space, in order 

 to raise the general temperature of the earth. Water, of all 

 substances in nature, seems to possess this quality to the great- 

 est extent ; and, besides, it is a fluid, and therefore adapted by 

 means of currents to carry the heat which it receives from the 

 sun to every region of the globe*. 



These results show (although they have reference to only one 

 stream) that the general influence of ocean-currents on the dis- 

 tribution of heat over the surface of the globe must be very great. 

 If the quantity of heat transferred from the equatorial regions 

 by the Gulf-stream alone is nearly equal to all the heat received 

 from the sun by the arctic regions, then how enormous must be 

 the quantity conveyed from the equatorial regions by all the 

 ocean-currents put together ! 



Influence of the Gulf-stream on the Climate of Europe. — In a 

 paper read before the British Association at Exeter, Mr. A. G. 

 Findlay objects to the conclusions at which I have arrived in 

 former papers on the subject, on these grounds, viz. : — 1st, that I 



* Trans, of Glasgow Geol. Soc. vol. ii. part 3. p. 185 ; Phil. Mag. Feb. 

 and June 1867. 



