Even then the air remained full of sand, while constantly shifting ridges made travel difficult.

Only grim necessity--the suffering of the ponies for water, and their own need for soon reaching the habitation of man and acquiring food--drove them to the early venture.

They must attain the valley of the Salt Fork that night, or else perish in the desert--there remained no other choice.

Tying neckerchiefs over their horses' eyes, and lying flat themselves, they succeeded in pressing slowly forward, winding in and out among the shifting dunes, with only the wind to guide them.

It was an awful trail, the hoofs sinking deep in drifting sand, the struggling ponies becoming so exhausted that their riders finally dismounted, and staggered forward on foot, leading them stumbling blindly after.