Physical geography. By Mary Somerville ...

CHAP. XVI. POLAR ICE. 215
ern termination is unknown. Facing America is a large island —Melville Island —with some others not extending so far north as
those mentioned; consequently all of them may be considered continental islands. As there are no large islands very far from land
in the other great oceans, there is reason to presume that the same
structure may prevail here also, and consequently it may be open
sea at the north pole. Possibly also it may be free from ice, for
Admiral Wrangel found a wide and open sea, free from ice and
navigable, beginning 16 miles north of the island of Kotelnoi, and
extending to the meridian of Cape Jackan. In fine summers the
ice suddenly clears away and leaves an open channel of sea along
the western coast of Spitzbergen from 60 to 150 miles wide, reaching to 80~ or even to 802~ N. latitude, probably owing to warm currents from low latitudes. It was through this channel that captain
Scoresby made his nearest approach to the pole. A direct course
from the Thames, across the pole to Behring's Straits, is 3570 geographical miles, while by Lancaster Sound it is 4660 miles. The
Russians would be saved a voyage of 18,800 geographical miles
could they go across the pole and through Behring's Straits to their
North American settlements, instead of going by Cape Horn.
Floating fields of ice, 20 or 30 miles in diameter, are frequent in
the Arctic Ocean: sometimes they extend 100 miles, so closely
packed together that no opening is left between them; their thickness, which varies from 10 to 40 feet, is not seen, as there is at least
two-thirds of the mass below water. Sometimes these fields, many
thousand millions of tons in weight, acquire a rotatory motion of
great velocity, dashing against one another with a tremendous collision. Packed ice always has a tendency to drift southwards, even
in the calmest weather; and in their progress the ice-fields are rent
in pieces by the swell of the sea. It is computed that 20,000 square
miles of drift-ice are annually brought by the current along the
coast of Greenland to Cape Farewell. In stormy weather the fields
and streams of ice are covered with haze and spray from constant
tremendous concussions; yet our seamen, undismayed by the appalling danger, boldly steer their ships amidst this hideous and discordant tumult.
Huge icebergs, and masses detached from the glaciers, which extend from the Arctic lands into the sea, especially in Baffin's Bay,
are drifted southwards 2000 miles from their origin to melt in the
Atlantic, where they cool the water sensibly for 30 or 40 miles
around, and the air to a much greater distance. They vary from a
few yards to miles in circumference, and rise hundreds of feet above
the surface. Seven hundred such masses have been seen at once in
the polar basin. When there is a swell, the loose ice dashing against
them raises the spray to their very summits; and as they waste away
they occasionally lose equilibrium and roll over, causing a swell