On all sides jackals howled dismally during the night; and above, during the day, an occasional vulture wheeled, fresh from the carcass of some poor mule dead by the wayside.

Such was the appearance of the land through which the caravan wound its way, beneath a sky peculiar to Arabia—­purple at night, white and terrible in its heat at noon, yet ever strange, weird and impressive.

But one incident worth recounting occurred on the way.  Yusuf, Amzi, and the boy Dumah had been traveling side by side for some time.  The way, at that particular spot, led over a plain which afforded comparatively easy traveling, and thus gave a better opportunity for conversation.  The talk had turned upon the Guebre worship, and the priest was amazed at the knowledge shown by Amzi of a religion so little known in Arabia.

“I can tell you more than that,” said Amzi in a low tone.  “I can tell you that you are not only Yusuf the Persian gentleman of leisure, but Yusuf the Magian priest, accustomed to feed the sacred fire in the Temple of Jupiter.  Is it not so?  Did not Yusuf’s hand even take the blood of Imri the infant daughter of Uzza in sacrifice?  Can Yusuf the Persian traveler deny that?”

Yusuf’s head sank; his face crimsoned with pain, and the veins swelled like cords on his brow.

“Alas, Amzi, it is but too true!” he said.  “Yet, upon the most sacred oath that a Persian can swear, I did it thinking that the blessing of the gods would thus be invoked.  The rite is one not unknown among the Sabaeans of to-day, and common even among the Magians of the past.  Amzi, it was in my days of heathendom that I did it, thinking it a duty to Heaven.  It was Yusuf the priest who did it, not Yusuf the man; yet Yusuf the man bears the torture of it in his bosom, and seeks forgiveness for the blackest spot in his life!  How knew you this, Amzi?—­if the question be an honorable one.”

“Amzi knows much,” returned the Meccan.  “He knows, too, that Yusuf can never escape the brand of the priesthood.  See!”

He leaned forward, and drew back the loose garment from the Persian’s breast.  A red burn, or scar, in the form of a torch, appeared in the flesh.  As Yusuf hastened to cover it, a head was thrust forward, and two bead-like eyes peered from a shrouded face.  It was the little dervish.

The priest was annoyed at the intrusion.  He determined to take note of the meddler, but the occurrence of an event common in the desert drove all thought of the dervish from his mind.

The cry “A simoom!  A simoom!” arose throughout the caravan.

There, far towards the horizon, was a dense mass of dull, copper-colored cloud, rising and surging like the waves of a mad ocean.  It spread rapidly upwards toward the zenith, and a dull roar sounded from afar off, broken by a peculiar shrieking whistle.  And now dense columns could be seen, bent backward in trailing wreaths of copper at the top, changing and swaying before the hurricane, yet ever holding the form of vapory, yellow pillars,—­huge shafts extending from earth to heaven, and rapidly advancing with awful menace upon the terrified multitude.