"Take your seats, gentlemen," he said, with a smile which went far to reassure them. "Now, we are ready, save for the fact that our engine is not yet running, while the doors of this sunken hangar are not open. But I pull this cord hanging overhead. See! An electric motor raises the whole shed and opens it. Then we press this little pedal--more electricity, my friends--a six-volt battery feeds a small motor aboard here and turns the engine round. Now air is forced through my paraffin carburettor and the vapour resulting is fed to that gasometer in the bows of the boat. Yes, it's a gasometer, just as you see on land, though much smaller. Thence the gas passes to the engine, where it receives more air and--ah! she's off. Listen to her humming, and for one moment notice the position of the engine. It is centrally placed, immediately beneath the planes, and is suspended from a single point. Thus it is free to swing both backward and forward and from side to side. There lies the secret of automatic stability. Say we are coasting along and a gust cants us to the right. The heavy engine still keeps in the same vertical position, while this whole machine turns as it were on that single point. You can readily follow that certain levers attached to engine and machine will be altered in position, and as a direct result the wing tips are warped in a prearranged manner, the back planes rotate upward or downward, or the rudder itself is operated. That is for coasting, for use when on a long, straight flight, when one wishes to take note of one's surroundings, to eat, or even to sleep." "Sleep!" gasped the Major. "Why not?" came Joe's cool answer. "But up in the air, thousands of feet up!" "As well there as within a hundred feet. The action I have been describing is automatic. There is no question of human error in its behaviour. So long as the planes have room for manoeuvring, and the engine does not stop, there is no need to interfere in the slightest. Set your course, lock your tiller, and go to sleep. But you shall see; for the moment I will trust to my own skill in manoeuvring. In fact, by pulling this small lever I secure the engine. In effect it is now suspended not only from a single point, but fixed rigidly to the framework of the whole machine. Then if I wish to bank, no automatic action can disturb my calculations. We are ready, I think. Look! flexible tubes above the engine carry the water from the force pumps to the motors on the hubs of the two propellers. There you see precisely the same hydraulic system of conveying power as is used elsewhere in this airship. No need, therefore, to have a dozen men holding the machine down, for the propellers are motionless, the bypass being full open. But I close it now--watch them twirl. I shut it almost completely----" "Hi! Hold on!" shouted Dick at that instant, while the Colonel gripped the sides of the cab and actually dropped his monocle.