When they started the actions of the dog showed Hare that Wolf was not tracking a back-trail, but travelling by instinct.  There were draws which necessitated a search for a crossing, and areas of broken rock which had to be rounded, and steep flat mesas rising in the path, and strips of deep sand and canyons impassable for long distances.  But the dog always found a way and always came back to a line with the black spur that Hare had marked.  It still stood in sharp relief, no nearer than before, receding with every step, an illusive landmark, which Hare began to distrust.

Then quite suddenly it vanished in the ragged blue mass of the Ghost Mountains.  Hare had seen them several times, though never so distinctly.  The purple tips, the bold rock-ribs, the shadowed canyons, so sharp and clear in the morning light—­how impossible to believe that these were only the deceit of the desert mirage!  Yet so they were; even for the Navajos they were spirit-mountains.

The splintered desert-floor merged into an area of sand.  Wolf slowed his trot, and Silvermane’s hoofs sunk deep.  Dismounting Hare labored beside him, and felt the heat steal through his boots and burn the soles of his feet.  Hare plodded onward, stopping once to tie another moccasin on Wolf’s worn paw, this time the left one; and often he pulled the stopper from the water-bag and cooled his parching lips and throat.  The waves of the sand-dunes were as the waves of the ocean.  He did not look backward, dreading to see what little progress he had made.  Ahead were miles on miles of graceful heaps, swelling mounds, crested ridges, all different, yet regular and rhythmical, drift on drift, dune on dune, in endless waves.  Wisps of sand were whipped from their summits in white ribbons and wreaths, and pale clouds of sand shrouded little hollows.  The morning breeze, rising out of the west, approached in a rippling lines like the crest of an inflowing tide.

Silvermane snorted, lifted his ears and looked westward toward a yellow pall which swooped up from the desert.

“Sand-storm,” said Hare, and calling Wolf he made for the nearest rock that was large enough to shelter them.  The whirling sand-cloud mushroomed into an enormous desert covering, engulfing the dunes, obscuring the light.  The sunlight failed; the day turned to gloom.  Then an eddying fog of sand and dust enveloped Hare.  His last glimpse before he covered his face with a silk handkerchief was of sheets of sand streaming past his shelter.  The storm came with a low, soft, hissing roar, like the sound in a sea-shell magnified.  Breathing through the handkerchief Hare avoided inhaling the sand which beat against his face, but the finer dust particles filtered through and stifled him.  At first he felt that he would suffocate, and he coughed and gasped; but presently, when the thicker sand-clouds had passed, he managed to get air enough to breathe.  Then he waited patiently while the steady seeping rustle