As the earth faded behind them they began to feel distinctly a warm and pungent wind that rose beneath--a steady current, as from some huge chimney that lazily was pouring out its monstrous volume of hot vapors. Away and away behind them slid the lip of this gigantic gash across the world; and now already with the swift rush of the plane the solid earth had begun to fade and to grow dim. Stern only cast a glance at the sun and at his compass, hung there in gimbals before him, and with firm hand steadied the machine for the long problematical flight to westward. Behind them the sun kept even with their swift pace; and very far below and ahead, at times they thought to see the fleeing shadow of the biplane cast now and then on masses of formless vapor that rose from the unsounded deeps. Definitely committed now to this tremendous venture, both Stern and the girl settled themselves more firmly in their seats. No time to feel alarm, no time for introspection, or for thoughts of what might lie below, what fate theirs must be if the old Pauillac failed them now! No time save for confidence in the stout mechanism and in the skill of hand and brain that was driving the great planes, with a roaring rush like a gigantic gull, a swooping rise and fall in long arcs over the hills of air, across the vast enigma of that space! Stern's whole attention was fixed on driving, just on the manipulation of the swift machine. Exhaust and interplay, the rhythm of each whirling cam and shaft, the chatter of the cylinders, the droning diapason of the blades, all blent into one intricate yet perfect harmony of mechanism; and as a leader knows each instrument in the great orchestra and follows each, even as his eye reads the score, so Stern's keen ear analyzed each sound and action and reaction and knew all were in perfect tune and resonance. The machine--no early and experimental model, such as were used in the first days of flying, from 1900 to 1915, but one of the perfected and self-balancing types developed about 1920, the year when the Great Death had struck the world--responded nobly to his skill and care. From her landing-skids to the farthest tip of her ailerons she seemed alive, instinct with conscious and eager intelligence. Stern blessed her mentally with special pride and confidence in her mercury equalizing balances. Proud of his machine and of his skill, superb like Phaeton whirling the sun-chariot across the heavens, he gave her more and still more speed. Below nothing, nothing save vapors, with here and there an open space where showed the strange dull purple of the abyss. Above, to right, to left, nothing--absolute vacant space. Gone now was all sight of the land that they had left. Unlike balloonists who always see dense clouds or else the earth, they now saw nothing. All alone with the sun that rushed behind them in their skimming flight, they fled like wraiths across the emptiness of the great void.