The Madsen family on a day of dogsled travel in Cap Hope village, Greenland. (Emil Madsen is featured in the book What I Eat: Around the World in 80 Diets.) When the snow crust is hard enough to ensure that the dogs won't break through, they can pull the half-ton weight of the sled for hours on end. On level ground, the animals pull at about the pace of a running human, but the sleds can whip down hills so fast that drivers must step on the brake at the rear of the sled to avoid running over the dogs.