370 THE DEPTHS OF THE SEA. [CHAP. VIII. 
by this the body of superheated water which issues 
through the ‘narrows’ from the Gulf of Mexico), if 
it reaches this locality at all—which is very doubtful 
—could only affect the most superficial stratum; and 
the same may be said of the surface-drift caused 
by the prevalence of south-westerly winds, to which 
some have attributed the phenomena usually ac- 
counted for by the extension of the Gulf-stream to 
these regions. And the presence of the body of 
water which lies between 100 and 600 fathoms depth, 
and the range of whose temperature is from 48° 
(8°85 C.) to 42° (5°5 C.), can scarcely be accounted 
for on any other hypothesis than that of a great 
general movement of: equatorial water towards the 
polar area, of which movement the Gulf-stream con- 
stitutes a peculiar case, modified by local conditions. 
In like manner the arctic stream which underlies 
the warm superficial strata in our cold area, con- 
stitutes a peculiar case, modified by the local condi- 
tions, to be presently explained, of a great general 
movement of polar water towards the equatorial 
area, which depresses the temperature of the deepest 
parts of the great oceanic basins nearly to the 
freezing-point.”’ | 
At first Dr. Carpenter appears to have regarded 
this oceanic circulation as a case of simple convection. 
‘“«'To what, then, is the north-east movement of the 
warm upper stratum of the North Atlantic attri- 
butable? JI have attempted to show that it is part 
of a general interchange between polar and equa- 
torial waters, which is quite independent of any such 
' A Lecture delivered at the Royal Institution, abstracted with 
the Author's signature in Vature, vol. i. p. 488 (March 10th, 187 0). 
