Page:The ocean and its wonders.djvu/184

 sink. Dining the first part of its journey, as we know, its great heat prevails over the other influence, and it flows as a surface-current. But, at a certain point in its northward route, it meets with the cold, brackish, ice-bearing currents that flow out of the arctic basin. Having lost much of its heat (though still possessing a great deal more than the arctic currents), the saltness of the Gulf Stream prevails; it dips below the polar waters, and thenceforth continues its course as an under-current, salt, and comparatively warm.

To state the matter briefly: The hot water, which ought to keep on the surface because of its heat, is sunk by its superabundant salt; and the cold water, which ought to sink because of its cold, is buoyed on the surface because of its want of salt.

Now arises the question—What becomes of the great quantity of salt that is thus being carried perpetually into the polar basin? Manifestly it must be carried out again by the surface-current, otherwise the polar basin would of necessity become a basin of salt. The under-current must, therefore, rise to the surface somewhere near the pole, with its temperature necessarily only a little, if at all, below the freezing-point—which, be it observed, is a warm temperature for such regions. Here, then, where the warm waters from the south rise to the surface, it is supposed this open Arctic Ocean must exist.