“You do?”
“Certainly; that’s what I said.”
“But how do you use it?”
“I’ll show you in a minute,” Fitz Mee answered complacently. “You know how they raise and lower gas balloons, don’t you?”
“Yes, I—I guess so,” the boy replied, a little dubiously. “The gas raises ’em.”
“Of course,” snapped the goblin, “that’s the lifting power, and feathers raise feather-bed balloons. But what do they use for ballast in gas balloons, eh?”
“Sand bags,” Bob answered.
“Yes,” the goblin pursued; “and when they want to go higher they throw out sand, don’t they?”
“Yes.”