“Ma goodness! Of all de ignerances I ever heard tell of!” groaned Rad. “I don’t see how you is ever gwine to git past Saint Peter, Koku.” Koku merely blinked. He was worried about Tom’s going up in the plane without him. But nothing much else disturbed his simple mind just then. Tom tried out the motors several times. The propellers worked perfectly. The hawsers holding the plane to the dock were thrown off, and then the big airship began to move. Tom headed her out into the lake. The crowd ashore cheered wildly as the nose of the great seaplane rose from the surface. She was then surrounded by a cloud of spray and her motors were roaring. She lifted more and more, and soon those ashore could see beneath the entire length of the boat’s keel. She hung above the water for a time, swerving in a quarter circle so as to head inshore again. Her wide wings and the two wheels underneath for land travel made the machine look like some huge winged insect or an antediluvian bird. The plane soared higher and higher, spiraling upward over the heads of the interested spectators. From the ground it seemed as though no such huge machine could be floated in the air. It must come crashing down to earth again! But still it mounted. Mr. Barton Swift, with binoculars at his eyes, watched the ascent with keen interest and some apprehension. He saw its wavering course, and realized that the balance of the huge plane was not at all perfect. Smaller and smaller grew the plane to the naked eye. That it wabbled in its course meant little to any of the spectators save the old inventor. He knew that the crew of the _Winged Arrow_ was in trouble, if not in danger! Suddenly the old gentleman was aware of the presence beside him of a man who likewise followed the course of the careening plane through binoculars. Mr. Swift cast a sharp glance upon this individual. He was very well dressed in a spick and span afternoon costume and wore a flower in his buttonhole. His dab of black mustache and goatee almost seemed painted upon his pale face. He brought the glasses down from his eyes and looked at Mr. Barton Swift. “What do you say, sir?” he asked. “Is she not making a heavy passage?” Mr. Swift was instantly cautious. Tom had not spoken to his father about this mysterious individual. But the old inventor had experienced so much interference on his own part from rivals, and had observed what Tom had sometimes suffered as well, that he was not likely to divulge his own private opinion to this stranger. “You understand,” he said quietly, “that no flying machine shoots into the sky like an arrow, even if it is named _Arrow_.” “True, true,” said the other eagerly. “It is a good point, sir. But there! You see?” He pointed again eagerly with his cane. “Did you see her roll then?” “An air-pocket, most likely,” Mr. Swift said calmly.