surface, there is, it is supposed, a basin in which the waters, as they rise to the surface, are at 30°, or whatever be the temperature of the under current, which we know must be above the freezing-point, for the current is of water in a fluid, not in a solid state. An arrangement in nature, by which a basin of considerable area in the frozen ocean could be supplied by water coming in at the bottom and rising up at the top, with a temperature not below 30°, or even 27°.2—the freezing-point of sea water—would go far to mitigate the climate in the regions round about.
425. Indications of a milder climate.—And that there is a warmer climate somewhere in that inhospitable sea, the observations of many of the explorers who have visited it indicate. Its existence may be inferred also from the well-known fact that the birds and animals are found at certain seasons migrating to the north, evidently in search of milder climates. The instincts of these dumb creatures are unerring, and we can imagine no mitigation of the climate in that direction, unless it arise from the proximity, or the presence there of a large body of open water. It is another furnace (§ 151) in the beautiful economy of Nature for tempering climates there.
426. How the littoral waters, by being diluted from the rivers and the rains, serve as a mantle for the Salter and warmer sea water below.—The hydrographic basin of the Arctic Ocean is large, and it delivers into that sea annually a very copious drainage. Such an immense volume of fresh water discharged into so small a sea as the Arctic Ocean is, must go far towards diluting its brine. Fig. 2, Plate X. (§ 433), shows the extent to which the brine of our littoral seas is diluted by the drainage from the Atlantic slopes of the United States. It will be observed by that figure that suddenly after crossing the parallel of 34° N. the water begins to grow cooler and lighter. The observations for the two curves are a part of the celebrated series made by Captain Rodgers in the U.S. ship "Vincennes" all the way from Behring's Straits by the way of Cape Horn to New York. He cleared the inner edge of the Gulf Stream in 34°, where the waters began to grow cooler and lighter, and so continued to do as he approached the shore. The remarkable and sudden approach of the thermal and specific gravity curves after crossing 34° N. can be explained by no other hypothesis than this, viz.: the surface water of the sea was so diluted with the fresh water from the Chesapeake, the Delaware, and New York Bays, that, notwithstanding the tem-
