"Two thousand pounds thrust!" called the engineer, as he looked at the scale.
"Let her go!" cried Tom, whose voice was hardly heard above the roar. The trim little aeroplane scudded over the ground, gathering speed at every revolution of the wheels. Then with a spring like that of some great bird launching itself in flight, she left the earth, and took to the air. Tom was off on his trip.
Those left behind sent up a cautious cheer, for they did not want to disturb Mr. Swift. They waved their hands to the young inventor, and he waved his in reply. Then he settled down for one of the swiftest flights he had ever undertaken.
Tom ascended until he struck a favorable current of air. There was a little wind blowing in the direction he wished to take, and that aided him. But even against a powerful head-wind the Humming-Bird could make progress.
The young inventor saw the ground slipping backward beneath him. Carefully he watched the various indicators, and listened intently to the sound of the cylinders' explosions. They came rapidly and regularly. The motor was working well.
Tom glanced at the barograph. It registered two thousand feet, and he decided to keep at
