an elevation of four hundred feet, as evidenced by the barograph.
"I guess this is high enough," remarked Tom after a bit. "Now to see if she'll stand still."
Slowly he moved the weights along, by means of the compound levers, until the air glider was on an "even keel" so to speak. It was still moving forward, with the wind now, for Tom had warped his wing tips.
"The thing to do," said the young inventor, "is to get it exactly parallel with the wind-strata, so that the gale will blow through the two sets of planes, just as the wind blows through a box kite. Only we have no string to hold us from moving. We have to depend on the equalization of friction on the surfaces of the wings. I wonder if I can do it."
It was a delicate operation, and Tom had not had much experience in that sort of thing, for his other airships and aeroplanes worked on an entirely different principle. But he moved the weights along inch by inch, and flexed the tips, planes and rudders until finally Ned, who was looking down through the floor window, cried out
"We're stationary!"
"Good!" exclaimed Tom. "Then it's a success."
