Three mules which could not rise were left where they lay, feebly struggling to regain their feet and follow their comrades, but falling back with hollow groanings and a kind of human despair in their faces.  Mile after mile the retreat continued, always at a walk, but without halting.  It was long before the Apaches were seen again, for the ascent of the plateau lost them a considerable space, and after that they were hidden for a time by its undulations.  But about four in the afternoon, while the emigrants were still at least five miles from the river, a group of savage horsemen rose on a knoll not more than three miles behind, and uttered a yell of triumph.  There was a brief panic, and another attempt to push the animals, which Thurstane checked with levelled pistol.

The train had already entered a gully.  As this gully advanced it rapidly broadened and deepened into a canon.  It was the track of an extinct river which had once flowed into the San Juan on its way to the distant Pacific.  Its windings hid the desired goal; the fugitives must plunge into it blindfold; whatever fate it brought them, they must accept it.  They were like men who should enter the cavern of unknown goblins to escape from demons who were following visibly on their footsteps.

From time to time they heard ferocious yells in their rear, and beheld their fiendish pursuers, now also in the canon.  It was like Christian tracking the Valley of the Shadow of Death, and listening to the screams and curses of devils.  At every reappearance of the Apaches they had diminished the distance between themselves and their expected prey, and at last they were evidently not more than a mile behind.  But there in sight was the river; there, enclosed in one of its bends, was an alluvial plain; rising from the extreme verge of the plain, and overhanging the stream, was a bluff; and on this bluff was what seemed to be a fortress.

Thurstane sent all the horsemen to the rear of the train, took post himself as the rearmost man, measured once more with his eye the space between his charge and the enemy, cast an anxious glance at the reeling beast which bore Clara, and in a firm ringing voice commanded a trot.

The order and the movement which followed it were answered by the Indians with a yell.  The monstrous and precipitous walls of the canon clamored back a fiendish mockery of echoes which seemed to call for the prowlers of the air to arrive quickly and devour their carrion.

CHAPTER XIX.

The scene was like one of Dore’s most extravagant designs of abysses and shadows.  The gorge through which swept this silent flight and screaming chase was not more than two hundred feet wide, while it was at least fifteen hundred feet deep, with walls that were mainly sheer precipices.

As the fugitives broke into a trot, the pursuers quickened their pace to a slow canter.  No faster; they were too wise to rush within range of riflemen who could neither be headed off nor flanked; and their hardy mustangs were nearly at the last gasp with thirst and with the fatigue of this tremendous journey.  Four hundred yards apart the two parties emerged from the sublime portal of the canon and entered upon the little alluvial plain.