ARCTIC ICE SLEDGING 195 



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 pick- 

 axes, 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 



