c1900  (1963)  Way up north there's a railroad, That was built on a track of gold; It followed the tracks of the mushers, Where they grasped the rocks for a hold.
1921  A musher in soft wet snow can only go at a certain pace. Any attempt to quicken the pace results only in a fall. The shoe cannot be pushed ahead as when the snow is well-packed or crusted. It has to be deliberately lifted, putting the leg tendons to an unnatural strain.
1958  The volunteer was no hardened musher, but a steamboat man named George Williams, who with an Indian companion set off on a terrifying journey