OCEANIC CIRCULATION. 249 



water of the Atlantic in the same latitudes, exposed to 

 the same average degree of heat, is not rendered heavier, 

 it may be maintained not unreasonably that the 

 water of the equatorial Atlantic being unconfined, 

 will in like manner not be rendered heavier by 

 evaporation. It seems to me that we have here a 

 positive argument of great weight in favour of my 

 views. But independently of this I would ask whether 

 it can be questioned that enormous evaporation does 

 take place over the equatorial area. This is what I 

 contend for, and I should have imagined that few would 

 undertake to deny the proposition. 



In passing, I must remark that I do not adopt the 

 distinction between equatorial and tropical water which 

 Dr. Carpenter appears to recognise. I have in view 

 the evaporation over an enormously larger area than he 

 considers no less an area, in fact, than the whole 

 ocean between latitudes 40 north and south of the 

 equator (at the equinoxes, and varying according to 

 the season). It by no means follows that because the 

 equatorial current does not cover this enormous area, 

 therefore the relation which I have suggested as 

 the mainspring of oceanic circulation has not that 

 extent. On the contrary, while it is on the one hand 

 certain that there is an excess of heat over this 

 enormous area, it is on the other almost a necessity 

 of my theory that the resulting current should be found 

 running along the middle only of the great region of 

 evaporation. 



This brings me to Dr. Carpenter's second objection, 



