"Ha! Whut I tell yo', Giant!" boasted the colored man. It was
his turn to smile.

"And so," went on Tom, judicially, "I guess I'll let Rad finish
spading the garden, and you, Koku, can come and help me lift some
heavy engine parts. Mr. Damon wants to explain something to me."

"Ha! Nothing what so heavy Koku not lift!" boasted the giant.

"Go on! Lift yo'se'f 'way from heah!" muttered Eradicate as he
picked up his dropped spade. And then, with a smile of
satisfaction, he fell to work in the mellow soil while Tom led
Koku to one of the shops where he set him to lifting heavy motor
parts about in order to get at a certain machine that was stored
away in the back of one of the rooms.

"That will keep him busy," said the young inventor. "And now,
Mr. Damon, I can listen to you. Do you really think you have a
new idea in airships?"

"I really think so, Tom. My Whizzer is bound to revolutionize
travel in the air. Let me tell you what I mean. Now cast your
mind back. How many ways are now used to propel an airship or a
dirigible balloon through the air? How many ways?"

"Two, as far as I know," said Tom. "At least there are only two
that have proved to be practical."

"Exactly," said Mr. Damon. "One with the propeller, or