It is evident that now, however powerful may be their means of defence, even more powerful than a network of torpedoes, Engineer Serko and Captain Spade are filled with an anxiety that they vainly essay to dissemble.  They hold frequent conferences together.  Maybe they discuss the advisability of quitting Back Cup with their wealth, for they are aware that if the existence of the cavern is known means will be found to reduce it, even if the inmates have to be starved out.

This is, of course, mere conjecture on my part.  What is essential to me is that they do not suspect me of having launched the keg that was so providentially picked up at Bermuda.  Never, I must say, has Engineer Serko ever made any allusion to any such probability.  No, I am not even suspected.  If the contrary were the case I am sufficiently acquainted with Ker Karraje to know that he would long ago have sent me to rejoin Lieutenant Davon and the Sword at the bottom of the lagoon.

The winter tempests have set in with a vengeance.  The wind howls though the hole in the roof, and rude gusts sweep through the forest of pillars producing sonorous sounds, so sonorous, so deep, that one might sometimes almost fancy they were produced by the firing of the guns of a squadron.  Flocks of seabirds take refuge in the cavern from the gale, and at intervals, when it lulls, almost deafen us with their screaming.

It is to be presumed that in such weather the schooner will make no attempt to put to sea, for the stock of provisions is ample enough to last all the season.  Moreover, I imagine the Count d’Artigas will not be so eager in future to show his Ebba along the American coast, where he risks being received, not, as hitherto, with the consideration due to a wealthy yachtsman, but in the manner Ker Karraje so richly merits.

It occurs to me that if the apparition of the Sword was the commencement of a campaign against the island, a question of great moment relative to the future of Back Cup arises.

Therefore, one day, prudently, so as not to excite any suspicion, I ventured to pump Engineer Serko about it.

We were in the neighborhood of Thomas Roch’s laboratory, and had been conversing for some time, when Engineer Serko touched upon the extraordinary apparition of an English submarine boat in the lagoon.  On this occasion he seemed to incline to the view that it might have been a premeditated expedition against Ker Karraje.

“That is not my opinion,” I replied, in order to bring him to the question that I wanted to put to him.

“Why?” he demanded.

“Because if your retreat were known a fresh attempt, if not to penetrate to the cavern, at least to destroy Back Cup, would ere this have been made.”

“Destroy it!” cried Serko.  “It would be a dangerous undertaking, in view of the means of defence of which we now dispose.”

“They can know nothing about this matter, Mr. Serko.  It is not imagined, either in the new world or the old, that the abduction from Healthful House was effected for your especial benefit, or that you have succeeded in coming to terms with Thomas Roch for his invention.”