"Haven't you noticed what I was tinkering on at the other end of the shop?" queried Professor Henderson, in surprise.
"Why, I see that you have a long steel plank there, with some kind of a compressed air contrivance at one end," said Jack.
"Is that what you mean, Professor?" queried Mark.
"That, boys," said the scientist, with some pride, "is a modern catapult—an up-to-the-minute catapult which, had it been known to the ancients, would have enabled the hosts of Joshua, for instance, to batter down the walls of Jericho without the trouble of marching so many times around the city."
"And what has a compressed air catapult got to do with the Snowbird?" queried Jack. "You propose launching your flying machine in the usual way," said the professor. "I see you have wheel trucks all ready to slip under her. We will not use those wheels, boys. I have a better plan. We will launch the Snowbird into the air from my catapult."
"Great goodness, Professor!" cried Mark. "Is that practicable?"
"We'll know after we have tried it," retorted Professor Henderson, drily.
"How did you happen to start working on this catapult idea?" asked
Jack.
"Well, I can't tell you everything," replied the inventor, "for it is partly a secret."
"Huh," laughed Mark. "You're mysterious. You haven't joined forces with some department of our government, or with another country?"