Henri knew that such was the situation by the fervid remarks of his companion. But such was the angle of the aviators' perch that there could be no attack except from the front, and even that was a climbing approach. It occurred to Henri, considering the lay of the land, that lead was not the only effective substance with which to repel boarders. The ground was loaded with natural ammunition--loose rocks and rocks, thousands of them, from fist size up to a ton. "Hey, old scout," hailed the boy, "give them a dose of dornicks." Schneider took the hint with a burst of approbation. "Two heads are better than one," he facetiously declared, hauling off his greatcoat for greater freedom as a heaver. A dozen or more of the pursuing party were working up the acute elevation when the first huge stone thundered down the incline. The boulder made as clean a sweep as a well-placed ball in a bunch of ninepins. "A ten-strike!" whooped Schneider. "Set 'em up again in the other alley!" The Russians back-tracked for a time, finding a better range to fire at the defenders on the mountainside, and such was the fusillade that Schneider and Henri were compelled to stay in cover to save their skins. "They can't work that game, though, to support a scaling force," said Schneider, "for the same fire would catch the scalers. If they come any nearer we can fix them, all right. But what a mercy it is that they haven't a field gun with them." "As it is, we can't stave them off very long," added Henri. "When it gets dark the stone-rolling game won't work." "Let me tell you, young man, when that hour comes, all they'll find here will be an empty nest." The veteran had a moving plan up his sleeve, and the chief reason he had for making this stand was to give the injured captain a little more time to mend. A scalp wound was what had laid the officer low, and since recovering consciousness he had rallied remarkably. In the soldier's knapsack, which Henri had thoughtfully carried, notwithstanding the hasty leave-taking, was three days' rations, and the invalid had also been strengthened by the food his new friends prevailed upon him to swallow. During the day Schneider several times checked an effort of their foes to reach the height by starting a little avalanche of rocks at the critical moment. In the periods of enforced peace, he cast an eye about for a likely way for quick retreat. The way presented itself in the shape of a fallen pine that bridged a narrow pass, deeply dividing this isolated level from the mountain chain that widely extended back of the occupied position, and rose in serried crags to the very skyline. It was a nerve-testing prospect, alluring alone to a professional rope walker. "We'll tackle it in short order," resolutely declared Schneider, after final survey. CHAPTER XVIII. TRAILS THAT CROSSED.