196 THE NORTH POLE 



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 gradually cementing the ice masses 

 together, then the heavier ice will have been forced 

 toward the shore; and the edges of the ice-fields farther 

 out, where they come in contact, will have piled up into 

 a series of pressure ridges, one beyond the other, which 

 any one traveling northward from the land must go 

 over, as one would go over a series of hills. 



If, on the other hand, there has been little wind in 

 the fall, when the surface of the polar sea was becoming 

 cemented and frozen over, many of these great floes 

 will have been separated from other floes of a like size 

 and character, and there may be stretches of com- 

 paratively smooth, young, or new, ice between them. 

 If, after the winter has set in, there should still be violent 

 winds, much of this thinner ice may be crushed up by 

 the movement of the heavier floes; but if the winter 

 remains calm, this smoother ice may continue until the 

 general breaking up in the following summer. 



But the pressure ridges above described are not the 

 worst feature of the arctic ice. Far more troublesome 

 and dangerous are the "leads" (the whalers' term for 

 lanes of open water), which are caused by the movement 

 of the ice under the pressure of the wind and tides. 

 These are the ever-present nightmare of the traveler 



