Brennan was for turning back, arguing the uselessness of going further, and the necessity of water for the ponies.

“Come on, Jim,” he urged.  “Be sensible; we’ve lost the trail, and that’s no fault o’ ours.  An Apache Indian couldn’t trace a herd o’ steers through this sand.  And look ahead thar!  It’s worse, an’ more of it.  I’m for stalking Lacy at the springs.”  He stopped suddenly, staring southward as though he had seen a vision.  “Holy smoke!  What’s that?  By God!  It’s a wagon, Jim; an’ it come right up out of the earth.  There wasn’t no wagon there a second ago.”

CHAPTER XXX:  ON THE EDGE OF THE CLIFF

For a moment both men suspected that what they looked upon was a mirage—­its actual existence there in that place seemed impossible.  Yet there was no disputing the fact, that yonder in the very midst of that desolation of sand, a wagon drawn by straining horses was slowly moving directly toward them.  Westcott was first to grasp the truth, hastily jerking the marshal back to where the tired ponies stood with drooping heads behind the protection of the dune.

“It’s the same outfit coming back,” he explained.  “The Sunken Valley must be out there—­just a hole in the surface of the desert—­and that’s how that wagon popped up out of the earth the way it did.  I couldn’t believe my eyes.”

“Nor me neither,” and the marshal drew one of his guns, and held it dangling in his hand.  “I’m a bit flustered yet, but I reckon that’s about the truth.  Get them ponies round a bit more, an’ we’ll wait and see what’s behind that canvas.”

The distance must have been farther than it seemed, or else the travelling difficult, for it was some time before the heavy wagon and straining team drew near enough for the two watchers to determine definitely the character of the outfit.  Westcott lay outstretched on the far side of the dune, his hat beside him, and his eyes barely able to peer over the summit, ready to report observations to the marshal crouched below.

“It’s Moore’s team, all right,” he whispered back, “and Matt is driving them.  There isn’t any one else on the seat, so I guess he must be alone.”

“We can’t be sure of that,” returned Brennan, wise in guarding against surprises.  “There was another fellow with him on the out trip, and he might be lying down back in the wagon.  We’d better both of us hold ’em up.  I can hear the creak of the wheels now, so maybe you best slide down.  Is the outfit loaded?”

“Travelling light, I should say,” and Westcott, after one more glance, crept down the sand-heap and joined the waiting man below.  Both stood intent and ready, revolvers drawn, listening.  The heavy wheels grated in the sand, the driver whistling to while away the dreary pull and the horses breathing heavily.  Moore pulled them up with a jerk, as two figures leaped into view, his whistle coming to an abrupt pause.