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." She nodded and smiled back at him, her white teeth gleaming in the strange, bluish light that now enveloped them. Stern, keenly attentive to the engine, advanced the spark another notch, and now the needle crept to 102 1/2. "We'll be across before we know it," thought he. "At this rate, I shouldn't be surprised to sight land any minute now." A quarter-hour more the Pauillac swooped along, cradling in her swift flight to westward. But all at once the man started violently. Forward he bent, staring with widened eyes at the tube of the fuel-gage. He blinked, as though to convince himself he had not seen aright, then stared again; and as he looked a sudden grayness overspread his face. "_What?_" he exclaimed, then raised his head and for a moment sniffed, as though to catch some odor, elusive yet ominous, which he had for some time half sensed yet paid no heed to. Then suddenly he knew the truth; and with a cry of fear bent, peering at the fuel-tank. There, quivering suspended from the metal edge of the aluminum tank, hung a single clear white drop--_alcohol!_ Even as Stern looked it fell, and at once another took its place, and was shaken off only to be succeeded by a third, a fourth, a fifth! The man understood. The ancient metal, corroded almost through from the inside, had been eaten away. That very morning a hole had formed in the tank. And now a leak--existing since what moment he could not tell--was draining the very life-blood of the machine. "The alcohol!" cried Stern in a hoarse, terrible voice, his wide eyes denoting his agitation. With a quivering hand he pointed. "My God! It's all leaked out--there's not a quart left in the tank! We're lost--lost in the bottomless abyss!" CHAPTER XXII LIGHTS!