Bill laughed. “That isn’t the half of it, boy. I’m telling you this much just so you can guide the ship while I put on my parachute. But here’s some more dope. These wheels are attached by wire cables to the ailerons, those hinged surfaces at the end of each wing. Their function, as they say in the Air Service, is primarily to impress a rolling movement to the airplane; just as the elevators are to impress a pitching movement. You see, in flying a plane, one not only has to steer it and balance it for the roll to either side like riding a bicycle,—the plane has to be balanced for the pitch fore and aft as well.”