In the northern sea, between Spitzbergen and the continent of America, there is a strong current, which always comes from the north, and sets southwardly.[22] It has been stated by some, that, in the spring season of the year, the water of this current is warmer and fresher than the surrounding water of the sea. Various other currents have, at different times, been observed, in different parts of the sea, setting from the north. Floating southwardly on these currents, have been seen large masses of ice, from fresh water rivers, with wolves and bears occasionally on them. New fallen trees have also been seen floating from the north; and various kinds of timber, some of which the species have hitherto been unknown, are frequently found lodged on the northern part of the coast of Norway, having drifted from some region still farther north. Trees have also been found floating in the ocean at latitude eighty degrees; when no timber is known to grow north of latitude seventy degrees. Also, seeds unknown to our botanists, and those of tropical plants have been found drifted on the coast of Norway, and parts adjacent, many of which were in so fresh a state as to vegetate and grow;[23] when it is well known that no plant of their species comes to perfection in any known climate far without the tropics. And, what makes the matter particularly extraordinary, is, that these things appear to be drifted by currents coming from the north; when, according to the old theory, we must believe the sea to be always frozen at the poles, which would render it difficult, if not impossible, to account for the existence of the currents at all. In the United States of America, and in Europe, the Aurora Borealis is always seen to the north: But many of those travellers and navigators, who penetrated to high northern latitudes, observed the Aurora Borealis in the south, and never in the north. The region in which it is believed to exist, is supposed to be about the place where the verge commences, and about fifty or sixty miles above the plane of the earth's surface; and that the travellers who discovered these appearances south of them, were at that time beyond the verge.