only Hawkins' Auto-aero-mobile! That's what it is!"

"Another invention!" I gasped.

"Yes, another invention. What the deuce are you turning pale about?"

"Well, your inventions, Hawkins--"

"Don't be such a coward, Griggs. Except that I had the body built of
aluminum, this is just an ordinary automobile. The invention lies in
the canopy. It's a balloon!"

"Is it--is it?" I said weakly.

"Yes, sir. Just at present it's a balloon with not quite enough gas in it
to counterbalance the pull of gravitation on the car and ourselves. I've
got two cylinders of compressed gas still connected with it. When I let
them feed automatically into the balloon, and then automatically drop
the iron cylinders themselves in to the road, we shall fairly bound over
the ground, because the balloon will just a trifle more than carry the
whole outfit."

"Well, don't waste all that good gas, Hawkins," I said hastily. "I can--I
can understand perfectly just how we should bound without that."

"Don't worry about the gas," smiled Hawkins placidly. "It costs
practically nothing. There! One of the cylinders is discharging now."

I glanced timidly above. Sure enough, the canopy was expanding slowly and
assuming a spherical shape.