When he has been taken in, Count d’Artigas and Engineer Serko follow.

Captain Spade and the crew of the Ebba remain behind, with the exception of four men who man the dinghy, which has been lowered. They have hold of a long hawser, with which the schooner is probably to be towed through the reef. Is there then a creek in the middle of the rocks where the vessel is secure from the breakers? Is this the port to which she belongs?

They row off with the hawser and make the end fast to a ring in the reef. Then the crew on board haul on it and in five minutes the schooner is so completely lost to sight among the rocks that even the tip of her mast could not be seen from the sea.

Who in Bermuda imagines that a vessel is accustomed to lay up in this secret creek? Who in America would have any idea that the rich yachtsman so well known in all the eastern ports abides in the solitude of Back Cup mountain?

Twenty minutes later the dinghy returns with the four men towards the tug which was evidently waiting for them before proceeding—where?

They climb on board, the little boat is made fast astern, a movement is felt, the screw revolves rapidly and the tug skims along the surface to Back Cup, skirting the reefs to the south.

Three cable’s lengths further on, another tortuous canal is seen that leads to the island. Into this the tug enters. When it gets close inshore, an order is given to two men who jump out and haul the dinghy up on a narrow sandy beach out of the reach of wave or weed, and where it will be easily get-at-able when wanted.

This done the sailors return to the tug and Engineer Serko signs to me to go below.

A short iron ladder leads into a central cabin where various bales and packages are stored, and for which no doubt there was not room in the hold of the schooner. I am pushed into a side cabin, the door is shut upon me, and here I am once more a prisoner in profound darkness.

I recognize the cabin the moment I enter it. It is the place in which I spent so many long hours after our abduction from Healthful House, and in which I was confined until well out at sea off Pamlico Sound.

It is evident that Thomas Roch has been placed in a similar compartment.

A loud noise is heard, the banging of the lid as it closes, and the tug begins to sink as the water is admitted to the tanks.

This movement is succeeded by another—a movement that impels the boat through the water.

Three minutes later it stops, and I feel that we are rising to the surface again.

Another noise made by the lid being raised.

The door of my cabin opens, and I rush out and clamber on to the platform.

I look around and find that the tug has penetrated to the interior of Back Cup mountain.

This is the mysterious retreat where Count d’Artigas lives with his companions—out of the world, so to speak.

CHAPTER IX.

INSIDE BACK CUP

The next morning I am able to make a first inspection of the vast cavern of Back Cup. No one seeks to prevent me.

What a night I have passed! What strange visions I have seen! With what impatience I waited for morning!

I was conducted to a grotto about a hundred paces from the edge of the lake where the tug stopped. The grotto, twelve feet by ten, was lighted by an incandescent lamp, and fitted with an entrance door that was closed upon me.

I am not surprised that electricity is employed in lighting the interior of the cavern, as it is also used in the submarine boat. But where is it generated? Where does it come from? Is there a manufactory installed somewhere or other in this vast crypt, with machinery, dynamos and accumulators?

My cell is neatly furnished with a table on which provisions are spread, a bunk with bedding, a basket chair, a wash-hand-stand with toilet set, and a closet containing linen and various suits of clothes. In a drawer of the table I find paper, ink and pens.

My dinner consists of fresh fish, preserved meat, bread of excellent quality, ale and whisky; but I am so excited that I scarcely touch it. Yet I feel that I ought to fortify myself and recover my calmness of mind. I must and will solve the mystery surrounding the handful of men who burrow in the bowels of this island.

So it is under the carapace of Back Cup that Count d’Artigas has established himself! This cavity, the existence of which is not even suspected, is his home when he is not sailing in the Ebba along the coasts of the new world or the old. This is the unknown retreat he has discovered, to which access is obtained by a submarine passage twelve or fifteen feet below the surface of the ocean.

Why has he severed himself from the world? What has been his past? If, as I suspect, this name of d’Artigas and this title of Count are assumed, what motive has he for hiding his identity? Has he been banished, is he an outcast of society that he should have selected this place above all others? Am I not in the power of an evildoer anxious to ensure impunity for his crimes and to defy the law by seeking refuge in this undiscoverable burrow? I have the right of supposing anything in the case of this suspicious foreigner, and I exercise it.

Then the question to which I have never been able to suggest a satisfactory answer once more surges into my mind. Why was Thomas Roch abducted from Healthful House in the manner already fully described? Does the Count d’Artigas hope to force from him the secret of his fulgurator with a view to utilizing it for the defence of Back Cup in case his retreat should by chance be discovered? Hardly. It would be easy enough to starve the gang out of Back Cup, by preventing the tug from supplying them with provisions. On the other hand, the schooner could never break through the investing lines, and if she did her description would be known in every port. In this event, of what possible use would Thomas Roch’s invention be to the Count d’Artigas Decidedly, I cannot understand it!

About seven o’clock in the morning I jump out of bed. If I am a prisoner in the cavern I am at least not imprisoned in my grotto cell. The door yields when I turn the handle and push against it, and I walk out.

Thirty yards in front of me is a rocky plane, forming a sort of quay that extends to right and left. Several sailors of the Ebba are engaged in landing bales and stores from the interior of the tug, which lays alongside a little stone jetty.

A dim light to which my eyes soon grow accustomed envelops the cavern and comes from a hole in the centre of the roof, through which the blue sky can be seen.

“It is from that hole that the smoke which can be seen for such a distance issues,” I say to myself, and this discovery suggests a whole series of reflections.

Back Cup, then, is not a volcano, as was supposed—as I supposed myself. The flames that were seen a few years ago, and the columns of smoke that still rise were and are produced artificially. The detonations and rumblings that so alarmed the Bermudan fishers were not caused by the internal workings of nature. These various phenomena were fictitious. They manifested themselves at the mere will of the owner of the island, who wanted to scare away the inhabitants who resided on the coast. He succeeded, this Count d’Artigas, and remains the sole and undisputed monarch of the mountain. By exploding gunpowder, and burning seaweed swept up in inexhaustible quantities by the ocean, he has been able to simulate a volcano upon the point of eruption and effectually scare would-be settlers away!

The light becomes stronger as the sun rises higher, the daylight streams through the fictitious crater, and I shall soon be able to estimate the cavern’s dimensions. This is how I calculate:

Exteriorly the island of Back Cup, which is as nearly as possible circular, measures two hundred and fifty yards in circumference, and presents an interior superficies of about six acres. The sides of the mountain at its base vary in thickness from thirty to a hundred yards.

It therefore follows that this excavation practically occupies the whole of that part of Back Cup island which appears above water.