re fired one at a time, and at
spaced intervals we also know. That they could not explode of themselves
in that way seems certain.

"You will remember that the signals began more than an hour before
sunrise, and continued for at least half an hour afterwards. We know
that the signals were sent automatically. Why? Partly, no doubt, because
it was necessary that they be absolutely regular; but also because the
man who did this thing--who is himself, perhaps, the inventor of the
method--chose to make no confidants, to have no accomplices, and he
could not himself be in the hut to send the signals. Again you ask why.
Not because of danger of discovery, since there was no such danger. I
believe it was because it was necessary that he be somewhere else,
directing from an angle, perhaps, that other force, so mysterious and so
deadly. I seem to see two forces, travelling in converging lines, as two
bullets might travel, their point of meeting the magazines of _La
Liberte_. At the instant of their meeting, there is a shock, a spark--as
though flint and steel met--and the magazine explodes--first the forward
magazine, then the after magazine, then the main magazine--one, two,
three! This is all mere guesswork, you understand, sir," Crochard added,
in another tone, "but so I see it. And, after all, it is susceptible of
proof."

"What proof?" demanded Delcasse.

"If my theory is the true one," Crochard explained, "there must have
been, somewhere, another installation to create the intercepting force,
which, of course, must also be transmitted by ether waves, as wireless
is, if it is to penetrate wood and steel. It must have been within an
hour's walk--probably half an hour's walk--of the hut in the grove. For
remember, the mechanism there was set going an hour before sunrise, and
the man had then to reach his other mechanism, and have it ready to
start at sunrise. It is for us to discover the place where this second
mechanism was installed--and where it probably still remains."

"Yes, that would be proof," agreed Delcasse thoughtfully; "and for
myself, I will say that I believe your theory the right one. But you
have not yet explained the part played by the two watchers on the quay."

"Their part was that of watchers merely," said Crochard. "They were sent
there to observe and to report to their master--as they did."

"As they did?"

"Surely it is evident," Crochard explained, "that, if our theory is
true, they would hasten