Mr. J. Croll on the Physical Cause of Ocean-currents. 255 



improbable, that the compensating current flowing from the 

 Atlantic into the southern hemisphere is as cold as the Ant- 

 arctic current. But Dr. Carpenter admits that the quantity of 

 warm water flowing from the Atlantic in equatorial regions to- 

 wards the south is even greater than towards the north. a The 

 unrestricted communication/' he says, u which exists between 

 the Antarctic area and the great Southern Ocean-basins would 

 involve, if the doctrine of a general oceanic circulation be ad- 

 mitted, a much more considerable interchange of waters between 

 the Antarctic and the Equatorial areas than is possible in the 

 northern hemisphere ;; *. And as a proof that this is actually 

 the case, he adduces the fact known to navigators that in the 

 Southern Ocean there is a perceptible " set " of warm surface- 

 water towards the Antarctic Pole. 



We have already seen that, were it not for the great mass of 

 warm water which finds its way to the polar regions, the tem- 

 perature of these regions would be enormously lower than they 

 really are. It was seen also that the comparatively high tempe- 

 rature of North-eastern Europe was due also to the same cause. 

 But if it is doubtful whether the Gulf-stream reaches our shores, 

 and if it is true that, even supposing it did, it " could only affect 

 the most superficial stratum/' and that the great mass of warm 

 water found by Dr. Carpenter in his dredging-expeditions came di- 

 rectly from the equatorial regions, and not from the Gulf-stream, 

 then the principal part of the heating-effect must be attributed, 

 not to the Gulf-stream, but to the general flow of water from the 

 equatorial regions. It surely would not, then, be too much to 

 assume that the quantity of heat conveyed from equatorial re- 

 gions by this general flow of water into the North Atlantic is 

 at least equal to that conveyed by the Gulf-stream. Let us, then, 

 assume that the total quantity of heat conveyed from equatorial 

 regions into the North Atlantic and Arctic Ocean by all the 

 various processes, the Gulf-stream included, is equal to twice 

 that conveyed by the Gulf-stream. 



We shall now consider whether the area of the Atlantic to the 

 north of the equator is sufficient to supply the amount of heat 

 demanded by Dr. Carpenter's theory. 



The entire area of the Atlantic, extending from the equator 

 to the tropic of Cancer, including the Caribbean Sea and the 

 Gulf of Mexico, is about 7,700,000 square miles. In a former 

 part of this paperf it was shown that, even assuming the volume 

 of the Gulf-stream to be considerably less than one half what 

 either Sir John Herschel or Lieut. Maury estimates it to be, 

 the quantity of heat conveyed by the stream through the Straits 



* ' Nature/ vol. i. p. 541. Proc. Koy. Soc. vol. xviii. p. 473. 

 t Phil. Mag. S. 4. vol. xxxix. p. 89. 



