By referring to the circumpolar map, the reader will be able to form a more accurate judgment than he could from the most elaborate description. He will observe that about the North Pole of the earth there is an extensive sea, or, more properly, ocean, with an average diameter of more than two thousand miles. He will observe that this sea is almost completely surrounded by land, and that its shores are, for the most part, well defined,--the north coasts of Greenland and Grinnell Land, which project farthest into it, being alone undetermined. He will note that these shores occupy, to a certain extent, a uniform distance from the Pole, and are everywhere within the region of perpetual frost. He will remember that they are inhabited everywhere by people of the same race, to whom the soil yields no subsistence, who live exclusively by hunting and fishing, and confine their dwelling-places either to the coast or to the banks of the rivers which flow northward. He will observe that the long line of coast which gives lodgment to these Arctic nomads is interrupted in three principal places; and that through these the waters of the Polar Sea mingle with the waters of the Atlantic and Pacific Oceans,--these breaks being Baffin Bay, Behring Strait, and the broader opening between Greenland and Nova Zembla; and if he traces the currents on the map and follows the Gulf Stream as it flows northward, pouring the warm waters of the Tropic Zone through the broad gateway east of Spitzbergen and forcing out a return current of cold waters to the west of Spitzbergen and through Davis Strait, he will very readily comprehend why in this incessant displacement of the waters of the Pole by the waters of the Equator the great body of the former is never chilled to within several degrees of the freezing-point; and since it is probably as deep, as it is almost as broad, as the Atlantic between Europe and America, he will be prepared to understand that this vast body of water tempers the whole region with a warmth above that which is otherwise natural to it; and that the Almighty hand, in the all-wise dispensation of His power, has thus placed a bar to its congelation; and he will read in this another symbol of Nature's great law of circulation, which, giving water to the parched earth and moisture to the air, moderates as well the temperature of the zones--cooling the Tropic with a current of water from the Frigid, and warming the Frigid with a current from the Tropic.[11] [Footnote 11: The temperature of the air at the North Pole has furnished a fruitful theme of speculation, both in connection with the influence of the sea and of the sun. I have before me a highly instructive paper on the climate of the North Pole, read before the Royal Geographical Society of London, April 10th, 1865, by W. E. Hickson, Esq., from which I extract the following:--