At this moment, I saw the captain come from an opening in the rocks, probably a grotto, at the base of this cliff hidden in the fog. Occasionally, in the mists above, appeared the shadows of huge birds. Their raucous cries were the sole interruption to the profound silence. Who knows if they were not affrighted by the arrival of this formidable, winged monster, which they could not match either in might or speed.

Everything led me to believe that it was here that the Master of the World withdrew in the intervals between his prodigious journeys. Here was the garage of his automobile; the harbor of his boat; the hangar of his air-ship.

And now the "Terror" stood motionless at the bottom of this hollow. At last I could examine her; and it looked as if her owners had no intention of preventing me. The truth is that the commander seemed to take no more notice of my presence than before. His two companions joined him, and the three did not hesitate to enter together into the grotto I had seen. What a chance to study the machine, at least its exterior! As to its inner parts, probably I should never get beyond conjecture.

In fact, except for that of my cabin, the hatchways were closed; and it would be vain for me to attempt to open them. At any rate, it might be more interesting to find out what kind of propeller drove the "Terror" in these many transformations.

I jumped to the ground and found I was left at leisure, to proceed with this first examination.

The machine was as I have said spindle-shaped. The bow was sharper than the stern. The body was of aluminium, the wings of a substance whose nature I could not determine. The body rested on four wheels, about two feet in diameter. These had pneumatic tires so thick as to assure ease of movement at any speed. Their spokes spread out like paddles or battledores; and when the "Terror" moved either on or under the water, they must have increased her pace.

These wheels were not however, the principal propeller. 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. To employ it I must first be free. And after what I knew -- little as that really was -- the Master of the World would never release me.

There remained, it is true, the chance of escape. But would an opportunity ever present itself? If there could be none during the voyages of the "Terror," might there possibly be, while we remained in this retreat?

The first question to be solved was the location of this hollow. What communication did it have with the surrounding region? Could one only depart from it by a flying-machine? And in what part of the United States were we? Was it not reasonable to estimate, that our flight through the darkness had covered several hundred leagues?

There was one very natural hypothesis which deserved to be considered, if not actually accepted. What more natural harbor could there be for the "Terror" than the Great Eyrie? Was it too difficult a flight for our aviator to reach the summit? Could he not soar anywhere that the vultures and the eagles could? Did not that inaccessible Eyrie offer to the Master of the World just such a retreat as our police had been unable to discover, one in which he might well believe himself safe from all attacks? Moreover, the distance between Niagara Falls and this part of the Blueridge Mountains, did not exceed four hundred and fifty miles, a flight which would have been easy for the "Terror."

Yes, this idea more and more took possession of me.