"There's no doubt at all about it, to my mind, sir," replied John Ross. "That's the next thing Paul and I propose doing, although I expect we shall have a hard time getting enough money to meet the expense of materials.  Of course we shall have the regular type of gasoline engine in place of this pneumatic arrangement, as this principle won't apply to big machines.  I figure a 400 horse-power Liberty engine would carry such a machine two hundred miles an hour."