At this moment Engineer Serko quits Ker Karraje, whom he leaves with Captain Spade, and enters the cavern, no doubt to fetch Thomas Roch.

When Ker Karraje orders the latter to launch his engines against the ships will he remember what I told him? Will not his crime appear to him in all its horror? Will he refuse to obey? No, I am only too convinced of the contrary. It is useless to entertain any illusion on the subject. The inventor believes he is on his own property. They are going to attack it. He will defend it.

The five warships slowly advance, making for the point. Perhaps they imagine on board that Thomas Roch has not given up his last and greatest secret to the pirates--and, as a matter of fact, he had not done so when I threw the keg into the lagoon. If the commanders propose to land storming parties and the ships advance into the zone of danger there will soon be nothing left of them but bits of shapeless floating wreckage.

Here comes Thomas Roch accompanied by Engineer Serko. On issuing from the passage both go to the trestle that is pointing towards the leading warship.

Ker Karraje and Captain Spade are awaiting them.

As far as I am able to judge, Roch is calm. He knows what he is going to do. No hesitation troubles the soul of the hapless man whom hatred has led astray.

Between his fingers shines the glass phial containing the deflagrator liquid.

He then gazes towards the nearest ship, which is about five miles' distant.

She is a cruiser of about two thousand five hundred tons--not more.

She flies no flag, but from her build I take her to belong to a nation for which no Frenchman can entertain any particular regard.

The four other warships remain behind.

It is this cruiser which is to begin the attack.

Let her use her guns, then, since the pirates allow her to approach, and may the first of her projectiles strike Thomas Roch!

While Engineer Serko is estimating the distance, Roch places himself behind the trestle. Three engines are resting on it, charged with the explosive, and which are assured a long trajectory by the fusing matter without it being necessary to impart a gyratory movement to them--as in the case of Inventor Turpin's gyroscopic projectiles. Besides, if they drop within a few hundred yards of the vessel, they will be quite near enough to utterly destroy it.

The time has come.

"Thomas Roch!" Engineer Serko cries, and points to the cruiser.

The latter is steaming slowly towards the northwestern point of the island and is between four and five miles off.

Roch nods assent, and waves them back from the trestle.

Ker Karraje, Captain Spade and the others draw back about fifty paces.

Thomas Roch then takes the stopper from the phial which he holds in his right hand, and successively pours into a hole in the rear-end of each engine a few drops of the liquid, which mixes with the fusing matter.

Forty-five seconds elapse--the time necessary for the combination to be effected--forty-five seconds during which it seems to me that my heart ceases to beat.

A frightful whistling is then heard, and the three engines tear through the air, describing a prolonged curve at a height of three hundred feet, and pass the cruiser.

Have they missed it? Is the danger over?

No! the engines, after the manner of Artillery Captain Chapel's discoid projectile, return towards the doomed vessel like an Australian boomerang.

The next instant the air is shaken with a violence comparable to that which would be caused by the explosion of a magazine of melinite or dynamite, Back Cup Island trembles to its very foundations.

The cruiser has disappeared,--blown to pieces. The effect is that of the Zalinski shell, but centupled by the infinite power of Roch's fulgurator.

What shouts the bandits raise as they rush towards the extremity of the point! Ker Karraje, Engineer Serko, and Captain Spade remain rooted to the spot, hardly able to credit the evidence of their own eyes.

As to Thomas Roch, he stands with folded arms, and flashing eyes, his face radiant with pride and triumph.