#5) What way did the severe cold threaten the lives of man and dogs in this chapter 3?

Occasionally they break through the ice, and the dogs have to be thawed by a fire. Perrault is relentless. He cannot be daunted, and wants to clear the 400 miles to Dawson as soon as possible. Several times the sled is almost dragged under the ice, but each time Perrault manages to get them over the next crest.