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sheer and unimaginable force with which the floes are driven against the edge of the glacial fringe, just as farther out the pressure ridges are caused by the force with which the great floes themselves are crushed and smashed together by the force of the wind and the tides. These pressure ridges may be anywhere from a few feet to a few rods in height; they may be anywhere from a few rods to a quarter of a mile in width; the individual masses of ice of which they are composed may vary, respectively, from the size of a billiard ball to the size of a small house. Going over these pressure ridges one must pick his trail as best he can, often hacking his way with pickaxes, encouraging the dogs by whip and voice to follow the leader, lifting the five-hundred-pound loaded sledges over hummocks and up acclivities whose difficulties sometimes seem likely to tear the muscles from one's shoulder-blades. Between the pressure ridges are the old floes, more or less level. These floes, contrary to wide-spread and erroneous ideas, are not formed by direct freezing of the water of the Arctic Ocean. They are made up of great sheets of ice broken off from the glacial fringe of Grant Land and Greenland, and regions to the westward, which have drifted out into the polar sea. These fields of ice are anywhere from less than twenty to more than one hundred feet in thickness, and they are of all shapes and sizes. As a result of the constant movement of the ice during the brief summer, when great fields are detached from the glaciers and are driven hither and thither under the impulse of the wind and the tides--impinging against one another, splitting in two from the violence of contact with other large fields, crushing up the thinner ice between them, having their edges shattered and piled up into pressure ridges--the surface of the polar sea during the winter may be one of almost unimaginable unevenness and roughness. At least nine-tenths of the surface of the polar sea between Cape Columbia and the Pole is made up of these floes. The other one-tenth, the ice between the floes, is formed by the direct freezing of the sea water each autumn and winter. This ice never exceeds eight or ten feet in thickness. The weather conditions of the fall determine to a great extent the character of the ice surface of the polar sea during the following winter. If there have been continuous shoreward winds at the time when the increasing cold was g
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