Ker Karraje, Engineer Serko and the others follow him to seek shelter inside of Back Cup.

I will not return to the cavern at any price, even if I get killed by staying where I am.

I will jot down my final notes and when the French sailors land on the point I will go--

END OF ENGINEER SIMON HART'S NOTES.

CHAPTER XVIII.

ON BOARD THE "TONNANT."

After the failure of Lieutenant Davon's mission with the _Sword_, the English authorities waited in vain for the expedition to return, and the conviction at length gained ground that the bold sailors had perished; but whether the _Sword_ had been lost by striking against a rock or had been destroyed by Ker Karraje's pirates, could not, of course, be ascertained.

The object of the expedition, based upon the indications of the document found in the keg that was thrown up on the shore at St. George, was to carry off Thomas Roch ere his engines were completed. The French inventor having been recovered--without forgetting Engineer Simon Hart--he was to be handed over to the care of the Bermudan authorities. That done, there would be nothing to fear from his fulgurator when the island was attacked.

When, however, the _Sword_ had been given up for lost, another expedition of a different kind, was decided upon.

The time that had elapsed--nearly eight weeks--from the date of the document found in the keg, had to be taken into consideration. It was thought that during the interval, Ker Karraje might have gained possession of Roch's secrets.

An _entente_ concluded between the maritime powers, resulted in the sending of five warships to Bermudan waters. As there was a vast cavern inside Back Cup mountain, it was decided to attempt to bring the latter down like the walls of a bastion, by bombarding it with powerful modern artillery.

The squadron assembled at the entrance to the Chesapeake, in Virginia, and sailed for the archipelago, which was sighted on the evening of November 17.

The next morning the vessel selected for the first attack, steamed forward. It was about four and a half miles from the island, when three engines, after passing the vessel, swerved round and exploded about sixty yards from her. She sank immediately.

The effect of the explosion, which was superior to any previously obtained by new explosives, was instantaneous. Even at the distance they were from the spot where it occurred, the four remaining ships felt the shock severely.

Two things were to be deduced from this sudden catastrophe:

1.--The pirate Ker Karraje was in possession of Roch's fulgurator.

2.--The new engine possessed the destructive power attributed to it by its inventor.

After the disappearance of the unfortunate cruiser, the other vessels lowered boats to pick up a few survivors who were clinging to the floating wreckage.

Then it was that the signals were exchanged and the warships started towards the island.

The swiftest of them, the _Tonnant_, a French cruiser, forged ahead while the others forced their draught in an effort to catch up with her.

The _Tonnant_, at the risk of being blown to pieces in turn, penetrated the danger zone half a mile, and then ran up her flag while manoeuvring to bring her heavy guns into action.

From the bridge the officers could see Ker Karraje's band scattered on the rocks of the island.

The occasion was an excellent one for getting a shot at them before the bombardment of their retreat was begun, and fire was opened with the result that the pirates made a rush to get into the cavern.

A few minutes later there was a shock terrific enough to shake the sky down.

Where the mountain had been, naught but a heap of smoking, crumbling rocks was to be seen. Back Cup had become a group of jagged reefs against which the sea, that had been thrown back like a gigantic tidal wave, was beating and frothing.

What was the cause of the explosion?

Had it been voluntarily caused by the pirates when they realized that escape was impossible?

The _Tonnant_ had not been seriously damaged by the flying rocks.