7o Mr. H. H. Howorth on 



had he been aware that about one-fifth of all the heat 

 possessed by the Atlantic is actually derived from the 

 equator by means of the Gulf Stream, he would have 

 assigned a temperature to the equator and the poles, show- 

 ing much greater divergence. Ocean currents convey heat 

 to high latitudes, and aerial currents distribute it over the land. 

 " Exclude," says Dr. Croll, " the waters of the Pacific and 

 Atlantic from temperate and polar regions, and place them 

 at the equator, and nothing now existing on the Globe could 

 live in high latitudes " (id. 51). I have given a resume of Dr. 

 Croll's arguments on this question, not only because I believe 

 them to be substantially sound and incontrovertible, but 

 because his conclusions on this issue will be of service ata later 

 stage of my argument. The postulate then that the climate 

 of the earth is largely the result of the distribution of ocean 

 currents seems to me reasonable. This in effect means that 

 the climate is largely due to the effect of the great equa- 

 torial current, which is the main liquid reservoir of heat, 

 and of which the Gulf Stream in the Atlantic, the Kuro 

 Siwo in the Pacific, etc., etc., are mere prolongations and 

 branches. So far I raise no issues with Dr. Croll. 



The next postulate of Dr. Croll is that the ocean 

 currents are due to the blowing of the winds. Here 

 again I believe him to be substantially right, but as his 

 results on this head are still disputed by a considerable school 

 of physicists, especially abroad. I think it well to state his 

 arguments in some detail. 



The real cause of ocean currents exercised physical 

 writers from early days. The great majority of them at first,, 

 including Maltebrun and Humboldt, attributed them in 

 the main to the rotation of the earth, which was supposed in 

 some way to leave behind its loose envelope of water and 

 air as it moved along. But rotation, as Mr. Croll says, 

 exercises no influence in generating motion in any body 

 placed on the earth's surface. If this body, however, be 



