The work on the trestles for Roch’s engine goes steadily forward, and there are now no fewer than fifty engines.  If Ker Karraje and Engineer Serko are under the necessity of defending Back Cup, three or four will be sufficient to render the island unapproachable, as they will cover a zone which no vessel could enter without being blown to pieces.  And it occurs to me that they intend to put Back Cup in a state of defence after having argued as follows: 

“If the appearance of the Sword in the lagoon was due to chance the situation remains unchanged, and no power, not even England, will think of seeking for the Sword inside the cavern.  If, on the other hand, as the result of an incomprehensible revelation, it has been learned that Back Cup is become the retreat of Ker Karraje, if the expedition of the Sword was a first effort against the island, another of a different kind—­either a bombardment from a distance, or an attack by a landing party—­is to be expected.  Therefore, ere we can quit Back Cup and carry away our plunder, we shall have to defend ourselves by means of Roch’s fulgurator.”

In my opinion the rascals must have gone on to reason still further in this wise: 

“Is there any connection between the disclosure of our secret—­if it was, and however it may have been made—­and the double abduction from Healthful House?  Is it known that Thomas Roch and his keeper are confined in Back Cup?  Is it known that the abduction was effected in the interest of Ker Karraje?  Have Americans, English, French, Germans, and Russians reason to fear that an attack in force against the island would be doomed to failure?”

Ker Karraje must know very well that these powers would not hesitate to attack him, however great the danger might be.  The destruction of his lair is an urgent duty in the interest of public security and of humanity.  After sweeping the West Pacific the pirate and his companions are infesting the West Atlantic, and must be wiped out at all costs.

In any case, it is imperative that the inhabitants of Back Cup should be on their guard.  This fact is realized, and, from the day on which the Sword was destroyed, strict watch has been kept.  Thanks to the new passage, they are able to hide among the rocks without having recourse to the submarine tunnel to get there, and day and night a dozen sentries are posted about the island.  The moment a ship appears in sight the fact is at once made known inside the cavern.

Nothing occurs for some days, and the latter succeed each other with dreadful monotony.  The pirates, however, feel that Back Cup no longer enjoys its former security.  Every moment an alarm from the sentries posted outside is expected.  The situation is no longer the same since the advent of the Sword.  Gallant Lieutenant Davon, gallant crew, may England, may the civilized nations, never forget that you have sacrificed your lives in the cause of humanity!