radually 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 comparatively 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 over the frozen surface of the
polar ocean--on the upward journey for fear that they may prevent
further advance; on the return journey for fear they may cut him off
from the land and life, leaving him to wander about and starve to death
on the northern side. Their occurrence or non-occurrence is a thing
impossible to prophesy or calculate. They open without warning
immediately ahead of the traveler, following no apparent rule or law of
action. They are the unknown quantity of the polar equation.

Sometimes these leads are mere cracks running through old floes in
nearly a straight line. Sometimes they are zigzag lanes of water just
wide enough to be impossible to cross. Sometimes they are rivers of open
water from half a mile to two miles in width, stretching east and west
farther than the eye can see.

There are various ways of crossing the leads. One can go to the right or
the left, with the idea of finding some place where the opposite edges
of the ice are near enough together so that our long sledges can be
bridged across. Or, if there are indications that the lead is closing,
the traveler can wait until the ice comes quite together. If it is very
cold, one may wait until