ME. J. PEESTWICH ON STJBMAEINE TEMPEEATUEES. 
635 
by this surging-up of Arctic and Antarctic waters at or near the equator ; while other 
portions of those great bodies of water are deflected back and imperceptibly return the 
one to the north polar and the other to the south polar seas — in masses unaffected by 
the more active shallow drifts and currents sweeping over their surface, and whose 
course is influenced by trade-winds and the earth’s rotation ; for while the cold waters 
are found so comparatively near the surface in the equatorial regions, the presence, 
at depths, in both the polar seas, of bodies of water having a temperature far above 
not only that of the winter but the annual temperature of those latitudes, is equally 
well proved. Thus although the mean annual temperature of Spitzbergen does not 
exceed 18° F. (and Dove estimates'* the normal mean temperature of latitudes 80° 
to 90° at 4°*5 F.), we find that in the seas surrounding that island there is a submarine 
temperature of 34° to 35°, if not rather higher. In the same way in the Antarctic regions 
and in latitude 60° to 70° we there also find a submarine temperature nearly as highf. 
Thus there is a rise of from 6° to 8° Fahr. in descending from the surface to depths 
of 3000 feet to 4000 feet in the open polar seas, whereas in like depths in the equa- 
torial regions of the Atlantic there is a fall of not less than 40° F., extending at greater 
depths to about 50° F. 
There is every reason to believe that the open seas of the north polar regions are due, 
as suggested by Maury and others, to the influence of warm southern waters, though 
this is not, as supposed by those authors, owing to the action of the Gulf-stream J, but 
to the surging-up of these deeper warm strata ; and in the same way the open sea found 
by Cook, Weddell, Boss, and others, after passing the first barrier of ice in the south 
polar seas, may be due to a similar cause. The great body of water at 32° to 35° or 
36° F. extending to the depth of 4000 to 5000 feet or more, and passing by Spitzbergen, 
must ultimately be displaced and deflected by the colder and denser waters between 32° 
and 25 0- 4 of the polar regions, and rise to the surface ; and as the influx is constant, an 
equilibrium can only be maintained by an efflux as great to other areas. By Behring 
Strait, owing to its narrowness and shallowness, comparatively none passes ; but the 
surface-currents through Smith Sound, and the more intricate channels amongst the 
islands of the North- American coast and so down Baffin Bay, and that down the east 
coast of Greenland, originate doubtlessly with these effluent waters. The temperature- 
soundings to depths of 1000 feet in Baffin Bay are in accordance with this view ; for 
after passing the stratum affected by the diurnal variations, the water to about that 
depth, although there is no surface-current from the south, has generally a temperature 
of from 30° to 34°, while that at greater depths sinks at places to a point very closely 
* The mean summer temperature of Spitzbergen, according to Dote, is 34°‘5 E. 
t If, as we have reason to think, the observations of Sir James Eoss should require a larger correction than 
others, then the isotherms in the Antarctic and Southern Oceans will have to be raised, and the isotherm of 
35° will be replaced by one of 33° or 32° E. 
+ At the same time there cannot, I think, he any doubt of the influence of the Gulf-stream, as a shallow 
current, on the seas and northern shores of the British Islands and Norway. 
MDCCCLXXV. 4 Q 
