Their pace therefore varied from a rapid walk to a run, according as their "wind" and leg muscles supplied the needed endurance. Paul and Jerry found it pretty hard to keep up with the other boys during the last three-quarters of a mile, especially when they struck a poorly broken snowdrift or a stretch of ground covered with rocks or rough ice. They were quite elated, however, at their ability to keep their feet in these rough places, after seeing two of the larger boys slip and fall.