Tom was, however, not yet satisfied with his machine. For one thing he had found it impossible as yet to return to earth with any exactitude at a fixed spot. It was a matter of the nice adjustment of the horizontal with the vertical motion, and after repeated failures Tom comforted himself with the thought that it must be only after long practice that an engine driver could pull his locomotive up to a nicety. Obviously much more practice must be required when the task was infinitely more difficult.
Further, in spite of the jacket around the turbine, the heat generated was still too great to allow of travelling any great distance in safety, and the prospective usefulness of the aeroplane was discounted accordingly.
It was Mr. Greatorex who suggested a possible way out of the difficulty.
“Why not have two engines instead of one?” he said. “If one breaks down—why, there’s the other.”
“It means more weight,” said Tom ruefully, “and therefore less speed and less carrying capacity.”
“Well, there’s no hurry, is there? And as for carrying capacity—I don’t intend to tempt the fates, or run the risk of a smash-up like—who was it? Icarus? Thought so.”
Tom adopted the suggestion. He replaced his first engine by two somewhat smaller, so that if one became overheated there was the other in reserve. The lifting capacity and the speed of the airship were consequently diminished, but scarcely so much as Tom expected.
So far the experiments had been carried on with perfect secrecy. The enclosure was surrounded by trees, and Tom was always careful not to drive his machine above the level of their tops. But one day, a few months after Schwab’s visit, he was careering round, to the mingled admiration and terror of Timothy Ball watching him from the ground, when he was startled by an exclamation that certainly did not spring from the lips of that worthy. Timothy was a good quarter-mile away; the voice appeared to come from a spot almost vertically below the aeroplane.
“By George! Look there, Mops!”
Tom took a hurried peep over. There, below him, in a gap between the trees just beyond the inner fence, stood a tall young fellow in tennis flannels, with light blue cap and tie.