y some day to defend Back
Cup and prevent any ship from approaching it----. It is true," he went
on, without finishing the reflection, "our retreat would have to have
been discovered by accident--or by denunciation."

"We have nothing to fear either from accident or denunciation,"
affirmed Serko.

"By one of our band, no, of course not, but by Simon Hart, perhaps."

"Hart!" exclaimed Serko. "He would have to escape first and no one can
escape from Back Cup. I am, by the bye, interested in this Hart. He is
a colleague, after all, and I have always suspected that he knows more
about Roch's invention than he pretends. I will get round him so that
we shall soon be discussing physics, mechanics, and matters ballistic
like a couple of friends."

"No matter," replied the generous and sensible Count d'Artigas, "when
we are in full possession of the secret we had better get rid of the
fellow."

"We have plenty of time to do that, Ker Karraje."

"If God permits you to, you wretches," I muttered to myself, while my
heart thumped against my ribs.

And yet, without the intervention of Providence, what hope is there
for me?

The conversation then took another direction.

"Now that we know the composition of the explosive, Serko," said Ker
Karraje, "we must, at all cost, get that of the deflagrator from
Thomas Roch."

"Yes," replied Engineer Serko, "that is what I am trying to do.
Unfortunately, however, Roch positively refuses to discuss it. Still
he has already made a few drops of it with which those experiments
were made, and he will furnish as with some more to blow a hole
through the wall."

"But what about our expeditions at sea?" queried Ker Karraje.

"Patience! We shall end by getting Roch's thunderbolts entirely in our
own hand, and then----"

"Are you sure, Serko?"

"Quite sure,--by paying the price, Ker Karraje."

The conversation dropped at this point, and they strolled off without
having seen me--very luckily for me, I guess. If Engineer Serko spoke
up somewhat in defence of a colleague, Ker Karraje is apparently
animated with much less benevolent sentiments in regard to me. On the
least suspicion they would throw me into the lake, and if I ever got
through the tunnel, it would only be as a corpse carried out by the
ebbing tide.

_August 21_.--Engineer Serko has been prospecting with a view to
piercing the proposed passage through the wall, in such a way that its
existence will never be dreamed of o