The wind droned and sighed against the planes, while occasionally a stronger gust, striking the machine obliquely, rocked it gently. Then the aillerons, or balancing devices, attached to the main plane began to work automatically, some bending up, others down, in this way creating a difference in the air pressure which quickly restored the biplane to an even keel.
Bob Somers at length threw on full power. The pulsating roar of the engine and whirr of propeller blades were sent far off on the wind, carrying fear to the cattle browsing on the prairie below.
As mile after mile slipped behind them, the two boys saw with great satisfaction the cigar-shaped hull no longer appearing as a patch of gray but beginning to show distinctly the effects of light and shade. The chain of mountains, too, which hemmed in the plain was looming up faintly through a dark, murky atmosphere. One lone snow-capped peak shone delicately white.
As Bob sent the biplane nosing its way slightly higher, Cranny Beaumont’s thoughts were busy. So far, the “Border City” had not shown the slightest indication of descending; indeed, the big lad was quite certain that the runaway balloon was rising.
“Suppose we have to follow ’em right over the mountains,” he reflected.
Almost every theory he had ever heard explained regarding the vagaries or dangers of air currents rushed into his mind with disconcerting clearness. Each gust of wind which struck the planes gave him an unpleasant shock.
“How in the world will Bob Somers ever make a turn in a wind like this?” Cranny looked hard into the aviator’s face, as if to read his thoughts; but all he saw was a determined, set expression.
The jagged mountain crests were now cutting more crisply against the sky. A long line of undulating foot-hills, some forest-covered, others bald ridges, rolled back in ever-increasing height to the mountains beyond. And Cranny knew of many deep gorges, rushing torrents and high precipices which existed amid the wilderness.
Now they were traveling over the sheep country. Flocks of thousands covered the plains. The boys could see them, terrified by the flying machine, scampering wildly about, and forming masses of a grayish white that continually changed their outlines. Some distance off, a watercourse fringed with willows wound its snake-like way over the grass-covered floor. Swiftly the biplane approached this gleaming line, passed across and left it far behind.
The “Border City” was steadily growing larger. In a short time the two craft would be racing side by side. And what then?