"Throwing the cooling fan out of gear will do it," he said, in tones of satisfaction. "I've still something in hand. Covering the radiator and so protecting it from cold will do the trick nicely."
"Twenty-seven thousand feet. Twenty-eight," he read out. "Are all feeling strong and well?"
They were gathered about the engine-room, some crowding in that chamber itself, some at the top of the ladder leading from it, grouped in the gallery of the airship. And a queer collection they were, muffled to the eyes, more than one already shivering with cold, for it must be recollected that this feat of clambering upward demanded no personal efforts from crew or passengers. Had they been on the snow-clad slopes of Mount Everest, amidst its glaciers and its crevasses, the path upward would have been one continual struggle, a struggle made all the more difficult by the increasing thinness of the air. Indeed this thinness of the air is one of the chief difficulties to be encountered by those who would ascend to huge heights above sea-level. Mountain sickness, the giddiness and nausea which attack people at great elevations, must also be overcome, though here, aboard the giant airship, not one of the members aboard felt so much as lightness of the head. It was the cold which troubled them. Why, Private Larkin's nose was positively blue! It peeped out from above a huge muffler which he had wound round his neck.
"I never!" Hurst remarked, grinning at him, and then taking another breath of oxygen. "You ain't handsome, not 'arf."
"'Ere," grunted Larkin, "none of yer lip! I'm 'avin'——"
But at that moment the need for more oxygen assailed him, and he buried his mouth in the apparatus affixed to each cylinder. Indeed, but for those cylinders this ascent would have been practically impossible. As it was, the ship climbed steadily, remorselessly upward. They were above the thick bank of wet cloud now. Of a sudden the cold became intense, while Dick found himself shielding his eyes from the glare. For the sun's rays were reflected from the virgin snow slopes with a brilliance he had never before experienced.
"Twenty-nine thousand feet. The summit of Mount Everest," called Joe, fingering the tops of his cylinders and the cooling surface of his radiator somewhat anxiously. "We will attempt a landing, and then we will ascend once more."
The big engine purred a little louder. Had an expert been there he would not have been able to detect a single alarming sound from the mechanism of the airship. For there was, in fact, little to go wrong.
"Freezing up does not trouble me," Joe had explained as they were ascending, "for my radiator is cooled by paraffin, and you may expose that liquid to extremes of cold with little effect. Even if there were danger of its freezing, the explosions of the engine cause heat, which is absorbed by the paraffin, and I have taken steps, by throwing out of gear the cooling fan, to retain that heat. As for the rest, the same fluid passing through those lines of steel tubes to the motors overhead is constantly in action. The pressure applied to it tends to add to its temperature, so that there again we can defy the cold."