“You don’t?” muttered the goblin, in surprise and irritation.
“No, I don’t.”
“Why, compressed air’s heavier than ordinary air, isn’t it?”
“Yes, of course.”
“Well, then, when I get that tank full the balloon’s heavier; and the increased weight overcomes the buoyancy of the feathers, and down I come.”
“Oh!”—in open-mouth admiration,—“that’s great! And when you want to go up again you just let the compressed air out, don’t you?”
“Sure!” blinked the goblin. “I’ll show you.”
He caught hold of the anchor rope, jerked the hook loose from the window-sill, and wound up the slender line. Then he flew to the air apparatus and turned a cock. Immediately there was the hiss of pent air escaping through a hole in the bottom of the tank, and the balloon began to ascend—slowly and gently at first, then more swiftly.
When it was a short distance above the housetop Fitz Mee closed the cock, remarking: