By nine o'clock all was ready. Along the land a mild south wind was blowing. Though the day was probably the 5th of October or thereabout, no signs of autumn yet were blazoned in the forest. The morning was perfect, and the travelers' spirits rose in unison with the abounding beauty of the day.
Stern had given the Pauillac another final going over, tightening the stays and laterals, screwing up here a loosened nut, there a bolt, making certain all was in perfect order.
At nine-fifteen, after he had had a comforting pipe, they made a clean getaway, rising along the edge of the chasm, then soaring in huge spirals.
"I want all the altitude I can get," Stern shouted at the girl as they climbed steadily higher. "We may need it to coast on. And from a mile or two up maybe we can get a glimpse of the other side."
But though they ascended till the aneroid showed eight thousand five hundred feet, nothing met their gaze but the same pearly blue vapor which veiled the mystery before them. And Stern, satisfied now that nothing could be gained by any further ascent, turned the machine due west, and sent her skimming like a swallow out over the tremendous nothingness below.
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!