At length the day of the trial came, and the Humming-Bird was wheeled out of the shed. In spite of the fact that it was practically finished, there yet remained much to do on it. It was not painted or decorated, and looked rather crude. But what Tom wanted to know was how it would fly, what control he had over it, what speed it could make, and how it balanced. For it was, at best, very frail, and the least change in equilibrium might be fatal.

Before taking his place in the operator's seat Tom started the motor, and by means of a spring balance tested the thrust of the propellers. It was satisfactory, though he knew that when the engine had been run for some time, and had warmed up, it would do much better.

"All ready, I guess, Mr. Damon!" he called, and the odd gentleman took his place. Tom got up into his own seat, in front of several wheels and levers by which he operated the craft.

"Start the propeller!" he requested of Mr. Jackson, and soon the motor was spitting fire, while the big, fan-like blades were whirring around like wings of light. The engineer and Eradicate were holding back the Humming-Bird.

"Let her go!" cried Tom as he turned on more gasoline and further advanced the spark of the motor. The roar increased, the propeller looked like a solid circle of wood, and the trim little monoplane moved slowly across the rising ground, increasing its speed every second, until, like some graceful bird, it suddenly rose in the air as Tom tilted the wing tips, and soared splendidly aloft!

Chapter Ten

A Midnight Intruder

Tom Swift sent his wonderful little craft upward on a gentle slant. Higher and higher it rose above the ground. Now it topped the trees; now it was well over them.

On the earth below stood Mr. Swift, Mr. Jackson, Eradicate and Mrs. Baggert. They were the only witnesses of the trial flight, and as the aged inventor saw his son's latest design in aeroplanes circling in the air he gave a cheer of delight. It was too feeble for Tom to hear, but the lad, glancing down, saw his father waving his hand to him.