“Prayer stones,” answered the professor, after a casual glance. “They are the prayers of travelers to the gods of their city that they might have a prosperous journey. Those fragments of pottery indicate that a bowl, probably containing water, was set beside each pile.”

“A prosperous journey,” mused Don, as he thought of the object of his own search, and though he did not erect a similar pile, there was a prayer in his heart.

On the night of the second day they made their preparations to pitch camp. A tent was soon erected, and while Abdul fed, watered and tethered the camels, Ismillah prepared a meal that fully justified his master’s opinion of him as a cook.

After supper, the travelers stretched themselves out on the sands, enjoying the faint breeze that had sprung up after sunset and studying the splendor of the Egyptian sky, studded with stars that glowed like so many jewels. Above them spread the Milky Way, like a spray of silver dust.

“The Nile of the heavens,” murmured the professor.

“What do you mean?” asked Don.

“The old Egyptians considered the Milky Way the Nile of the future life,” was the answer. “They used to fancy that the departed ones were sailing up and down that, just as they used to sail the Nile when they were alive.”

“Quite a poetical fancy,” remarked the captain.

“How nice and homelike,” said the irreverent Teddy. “You could just look up and say, ‘There goes Aunt Jemima.’”

The professor looked rather shocked, but the captain laughed.