Suddenly Jo exclaimed, breathlessly, "Here's the place!" and then, to Rob's dismay, he took a flying leap off the parapet into the gulf of impenetrable blackness lying on the outer side of the wall.
For a moment the young American turned sick with the thought that, despairing of ultimate escape, his comrade had chosen death by suicide, and now lay lifeless at the foot of the lofty battlement.
Then came the familiar voice rising from some unknown depth, and calling on him to follow.
"Jump, Rob!" it cried; "you'll land all right, the same as I have."
Even with this assurance our lad hesitated to leap into the darkness. He knew that the wall was at least fifty feet high. There was at its bottom no moat filled with water, into which one might launch himself with safety. "Nor is there any pile of feather-beds, that I know of," he thought, grimly.
From both sides lines of torches were steadily advancing, while up from the city rose a tumult of angry voices. Only in the outside blackness that already had engulfed his friend was there the slightest promise of escape.
"I suppose there's nothing else to be done," he muttered, setting his teeth and bracing himself for the effort. "So, here goes!"
With this he sprang out into space and instantly vanished.
When, a minute later, the advancing lines of torch-bearers came together at that very point, they were bewildered and frightened by the absolute disappearance of those whom they had thought to be so surely within their grasp.
Certainly the magic of the foreign devils was stronger than their priests had led them to believe.
The great plain of northern China is composed of alluvial matter extending to an unknown depth, reddish-yellow in color, and possessed of wonderful fertility. When wet it packs closely; and later, under the influence of a hot sun, it bakes like clay. During seasons of drought it pulverizes to an almost impalpable dust that is blown by fierce winds into ridges and heaps like snow-drifts. These are piled high against obstructing walls, so that sometimes buildings standing in exposed situations are completely buried beneath them. Such a drift of fine sand had formed in an angle of the city wall, along which our lads fled; and Chinese Jo, knowing of it, had selected this as a point for escape.