door, into a field enclosed by a high fence. That is where I made all my trials, and the crowd couldn't get in, though some boys did find knotholes and use them. But I don't mind that. The only thing that bothers me is that I can't make the Whizzer go up, and if it won't go up, it certainly won't sail. That's my difficulty, and I hope you can remedy it, Tom Swift."
"I'll do the best I can. But let's get the airship outside."
This was soon accomplished, and in the open lot Tom made a thorough and careful examination of the mechanism. The motor was started, and the propellers, for there were two, whirled around at rapid speed.
Tom made some tests and calculations, at which he was an expert, and applied the brake test, to see how much horse power the motor would deliver.
"I think there is one trouble that we will have to get over," he finally said to Mr. Fenwick.
"What is that?"
"The motor is not quite powerful enough because of the way in which you have it geared up. I think by changing some of the cogs, and getting rid of the off-set shaft, also by increasing the number of revolutions, and perhaps by using a
