August 18.—­At one o’clock this morning I was roused by several detonations.

“Has Back Cup been attacked?” was my first thought.  “Has the schooner excited suspicion, and been chased to the entrance to the passes?  Is the island being bombarded with a view to its destruction?  Has justice at last overtaken these evil-doers ere Thomas Roch has been able to complete the manufacture of his explosive, and before the autopropulsive engine could be fetched from the continent?”

The detonations, which are very violent, continue, succeeding each other at regular intervals, and it occurs to me that if the schooner has been destroyed, all communication with the bases of supply being impossible, Back Cup cannot be provisioned.

It is true the tug would be able to land the Count d’Artigas somewhere on the American coast where, money being no object, he could easily buy or order another vessel.  But no matter.  If Back Cup is only destroyed before Ker Karraje has Roch’s fulgurator at his disposal I shall render thanks to heaven.

A few hours later, at the usual time, I quit my cell.  All is quiet at the Beehive.  The men are going about their business as usual.  The tug is moored near the jetty.  Thomas Roch is going to his laboratory, and Ker Karraje and Engineer Serko are tranquilly pacing backwards and forwards by the lake and chatting.  The island therefore could not have been attacked during the night.  Yet I was awakened by the report of cannon, this I will swear.

At this moment Ker Karraje goes off towards his abode and Engineer Serko, smilingly ironical, as usual, advances to meet me.

“Well, Mr. Simon Hart,” he says, “are you getting accustomed to your tranquil existence?  Do you appreciate at their just merit the advantages of this enchanted grotto?  Have you given up all hope of recovering your liberty some day or other?”

What is the use of waxing wroth with this jester?  I reply calmly: 

“No, sir.  I have not given up hope, and I still expect that I shall be released.”

“What!  Mr. Hart, separate ourselves from a man whom we all esteem—­and I from a colleague who perhaps, in the course of Thomas Roch’s fits of delirium, has learned some of his secrets?  You are not serious!”

So this is why they are keeping me a prisoner in Back Cup!  They suppose that I am in part familiar with Koch’s invention, and they hope to force me to tell what I know if Thomas Koch refuses to give up his secret.  This is the reason why I was kidnapped with him, and why I have not been accommodated with an involuntary plunge in the lagoon with a stone fastened to my neck.  I see it all now, and it is just as well to know it.

“Very serious,” I affirm, in response to the last remark of my interlocutor.

“Well,” he continues, “if I had the honor to be Simon Hart, the engineer, I should reason as follows:  ’Given, on the one hand, the personality of Ker Karraje, the reasons which incited him to select such a mysterious retreat as this cavern, the necessity of the said cavern being kept from any attempt to discover it, not only in the interest of the Count d’Artigas, but in that of his companions—­’”