When the Yukon would break was problematical.

Two thousand miles away it flowed into Bering Sea, and it was the ice conditions of Bering Sea that would determine when the Yukon could rid itself of the millions of tons of ice that cluttered its breast.
On the twelfth of May, carrying their sleeping-robes, a pail, an ax, and the precious rifle, the two men started down the river on the ice.
Their plan was to gain to the cached poling-boat they had seen, so that at the first open water they could launch it and drift with the stream to Sixty Mile.

In their weak condition, without food, the going was slow and difficult.

Elijah developed a habit of falling down and being unable to rise.

Daylight gave of his own strength to lift him to his feet, whereupon the older man would stagger automatically on until he stumbled and fell again.
On the day they should have reached the boat, Elijah collapsed utterly.
When Daylight raised him, he fell again.