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.
Stern glanced at the barometer, and grunted with surprise.
"H'm! Twelve thousand four hundred and fifty feet--and I've been jockeying to come down at least five hundred feet already!" thought he. "How the devil can that be?"
The explanation came to him. But it surprised him almost as much as the noted fact.
"Must be one devil of a wind blowing up out of that place," he pondered, "to carry us up nearly four thousand feet, when I've been trying to descend. Well, it's all right, anyhow--it all helps."
He looked at the spinning anemometer. It registered a speed of ninety-seven miles an hour. Yet now that they were out of sight of any land, only the rush of the wind and the enormous vibration of the plane conveyed an idea of motion. They might as well have been hung in mid-space, like Mohammed's tomb, as have been rushing forward; there was no visible means of judging what their motion really might be.
"Unique experience in the history of mankind!" shouted Stern to the girl. "The world's invisible to us."