Page:My Airships.djvu/117

 automobiles, free from great vibration, of the present. Nowadays, even the colossal 80 and 90 horse-power motors of the latest racing types can be started and stopped as gently as those great steel hammers in iron foundries, whose engineers make a trick of cracking the top of an egg with them without breaking the rest of the shell. My tandem motor of two cylinders, working the same connecting-rod and fed by a single carburator, realised 3$\tfrac{1}{2}$ horse-power—at that time a considerable force for its weight—and I had no idea how it would act off terra firma. I had seen motors "jump" along the highway. What would mine do in its little basket, that weighed almost nothing, and suspended from a balloon that weighed less than nothing? You know the principle of these motors? One may say that there is gasoline in a receptacle. Air passing through it comes out mixed with gasoline gas, ready to explode. You give a whirl to a crank, and the thing begins working automatically. The piston goes down, sucking combined gas and air into the cylinder. Then the piston comes back and compresses it. At that moment an electric spark is struck. An explosion follows instantly; and the piston goes down,