As the sky above was now clearing, from the elevation the aviators could see the brown and white summits of other hills, divided by valley cuttings, as far as the eye could reach. Schneider was just about to light his beloved briar pipe, when all of a sudden he dropped the ember he was lifting to the bowl, and pointed toward the high ground edging the opposite side of an intervening gulch to the right of their bivouac. A solitary horseman had ridden into view, and both rider and steed posed, statue-like, on the verge of the steeply descending slope. Roque like a flash covered the smouldering fire with a blanket, checking tell-tale spirals of smoke. Fixing a glass on the equestrian, Stanislaws uttered the one word--"Cossack." "He's our meat," snapped Schneider. "It's your first go this time," reluctantly conceded Stanislaws, who was himself aching to draw first blood. Schneider, taking general consent for granted, gave Henri a nod sidewise, and both moved as quickly as they could on all fours to their biplane. While the boy was getting the motors in play, the fighting observer shifted his carbine from shoulder to knee. The buzzing of the aëroplane had evidently caught the ear of the wild cavalryman across the gulch, for the horse was rearing, lifted by an unexpected wrench of the bit. Nothing, however, on four legs or two, would have a ghost of a chance to outdistance a racing aëroplane. Spur as he would, the horseman was overhauled in the space of three minutes. The aëroplane, skimming the earth, mixed its scattering of snow particles with those raised by the pounding hoofs of the wildly galloping horse. So close together were pursuer and pursued, that the Cossack's first lance thrust came within a hairline of reaching the ribs of Schneider, leaning forward in preparation to make a flying leap from the aircraft when it should lessen speed sufficiently to enable him to keep his feet when alighting on the stony soil. Why the observer did not immediately use carbine or revolver in return for the lance attack, queerly impressed the young pilot ahead, who, naturally, would expect such action on the part of his armed companion, gravely menaced by a wicked weapon too lengthy to be successfully resisted by counter strokes of a saber. Henri's second thought was that Schneider had been touched in a vital spot by the steel point, and that he, too, would next get into the deal of death. To send the machine aloft was a third thought, following in a flash, but the execution of this purpose was as quickly delayed by a motion indicating a lift of weight behind. Schneider had jumped from the biplane, now wheeling the ground, and within two lengths of a precipice, hitherto unobserved. The Cossack, on the very brink of this dizzy declivity, had jerked his horse to its haunches, at the same moment when Henri checked further movement of the biplane by a skillful side turn.