This consisted of two "Parsons" turbines placed on either side of the keel.

Driven with extreme rapidity by the engine, they urged the boat onward in the water by twin screws, and I even questioned if they were not powerful enough to propel the machine through the air.
The chief aerial support, however, was that of the great wings, now again in repose, and folded back along the sides.

Thus the theory of the "heavier than air" flying machine was employed by the inventor, a system which enabled him to dart through space with a speed probably superior to that of the largest birds.
As to the agent which set in action these various mechanisms, I repeat, it was, it could be, no other than electricity.

But from what source did his batteries get their power?
Had he somewhere an electric factory, to which he must return?
Were the dynamos, perhaps working in one of the caverns of this hollow?
The result of my examination was that, while I could see that the machine used wheels and turbine screws and wings, I knew nothing of either its engine, nor of the force which drove it.

To be sure, the discovery of this secret would be of little value to me.