I did not dare venture an inquiry for fear of arousing suspicion by evident ignorance of something which as a yellow man I should have known; but before we reached the city gate I was to learn the purpose of that grim shaft and the meaning of the mighty accumulation beneath it.

We had come almost to the gate when one of the party called to his fellows, at the same time pointing toward the distant southern horizon. Following the direction he indicated, my eyes descried the hull of a large flier approaching rapidly from above the crest of the encircling hills.

“Still other fools who would solve the mysteries of the forbidden north,” said the officer, half to himself. “Will they never cease their fatal curiosity?”

“Let us hope not,” answered one of the warriors, “for then what should we do for slaves and sport?”

“True; but what stupid beasts they are to continue to come to a region from whence none of them ever has returned.”

“Let us tarry and watch the end of this one,” suggested one of the men.

The officer looked toward the city.

“The watch has seen him,” he said; “we may remain, for we may be needed.”

I looked toward the city and saw several hundred warriors issuing from the nearest gate. They moved leisurely, as though there were no need for haste—nor was there, as I was presently to learn.

Then I turned my eyes once more toward the flier. She was moving rapidly toward the city, and when she had come close enough I was surprised to see that her propellers were idle.