It was nearly evening then, and until it was dark enough for his flight Tom spent the time tuning up the engine and seeing that all was in readiness for the latest test. He had decided not to go aloft while it was light enough for curiosity seekers to note the flight.
Tom rather wished Mary Nestor might have a sail with him in his latest improved silent Air Scout, but the girl was too much occupied at home and in trying to find some trace of her father.
Tom, his father, and Mr. Damon had helped all they could, but there were no results. A private detective had been engaged, but he had no more of a clew than the regular police.
At last it was dark enough for the flight, and Tom and Mr. Damon took their places in the machine. Once more the propellers were turned around, and when the compression had been made, and the spark switched on, around spun the big wooden blades, and the great craft moved over the grass.
On and on and up and up sailed Tom and Mr. Damon, and as they left behind them the shops and the Swift homestead, the two passengers were aware of their almost silent flight. The big aeroplane, the exhaust of which, ordinarily, would have nearly deafened them, was now as silent as a bird.
"Silent Sam for Uncle Sam!" cried Tom in delight, as he went on faster. "I'm sure the government ought to be glad to get this plane for air scout work. It's a success! A great success!"
"Yes, so it is!" agreed Mr. Damon. "You do well to speak of it so, Tom."
For, modest as the young inventor was, he felt, in justice to himself, that he must acknowledge the fact that his craft was a success. For it rose and sailed almost as silently as a bat, and a few hundred feet away no one, not seeing it, would have believed a big aeroplane was in motion.
Tom and Mr. Damon flew about twenty miles at a swift pace, and all the fault Tom had to find was that the machine was not as steady in flight as she should have been.
"But I can remedy that with the use of some of dad's gyroscope stabilizers," he told Mr. Damon.