A daily flight became part of the boys’ programme. They did not tell their uncle of the difficulties they had to contend with, but these were real enough. To start from and alight on so narrow a platform as the ledge furnished was in itself a severe test of airmanship; but the problems of actual flight were still more serious. The gorge was so narrow that it gave them little room for evolutions. There were only one or two spots, either up or down stream, at which they could turn with safety; and when the wind came in sudden gusts down the mountain side the act of turning, even in these comparatively open spaces, was attended with much danger. They could only avoid the peril by ascending to altitudes which as yet Bob was unwilling to attempt. But a few weeks’ practice developed in them a kind of instinct for dodging the risks to which the circumscribed space rendered them liable; and though they had one or two lucky escapes they met with no real mishap. All this time they got a good deal of quiet amusement out of their uncle’s attitude. At first he affected to regard the aeroplane as a plaything, and a somewhat dangerous plaything, much as an elderly person watching a child playing with fireworks expects him sooner or later to burn his fingers. In the early days of their flying he was indeed genuinely nervous, and tried by means of hints and warnings to wean them from their sport. But as time passed, and none of his fears were realised, they perceived that he was becoming less uneasy and more and more interested. One day he actually accompanied them to the shed, which he had never yet visited, and watched them as they drew the aeroplane out on to the ledge, made a methodical inspection of the engine, and prepared for their flight. "A neat piece of mechanism," he said. "Much stronger than it looks from a distance." Lawrence surreptitiously winked at Bob. "Yes, it’s strong enough," said Bob, smiling as he continued his task of cleaning one of the cylinders. "What load can you carry?" asked Mr. Appleton presently. "I don’t trust the Babu’s calculations." "A thousand pounds or more," replied Lawrence, who was examining the gearing of the propeller. "You’ve only two seats," Mr. Appleton went on, after an interval of silence. "Some machines will carry three, I suppose." "Oh yes," answered Bob. "We could easily rig up a third seat. Pity you dislike the thing so much, Uncle." Mr. Appleton did not reply. When the boys got into their places, he did not warn them to be careful, as his habit was, but bade them good-bye as unconcernedly as if they had been going for a short train journey. "He’s fishing for an invitation," said Lawrence to his brother as they rose into the air. "Bet you what you like we have him with us within a week."