“Let her go, then,” the commandant ordered the two men who had appeared to give the aëroplane a start.
A moment later and the machine was speeding along the ground.
“Good luck,” called the commandant.
Chester waved his hand in reply.
Now Hal touched the elevating lever, and the aëroplane left the ground, and, soaring high in the air, sped on its way.
“Which way, Chester?” Hal called back over his shoulder.
“Due east,” replied Chester, “but first rise as high as you can.”
Hal obeyed this command, and soon the two boys and a dog were thousands of feet above the earth.
“What’s your altitude?” called Chester.