d tragedy.

"Professor," said Natas, in quick, stern tones, "I am not accustomed
to say what is not true, nor yet to be contradicted by any one in
human shape. Stand there till I tell you to move."

As he spoke these last words Natas made a swift, sweeping downward
movement with one of his hands, and fixed his eyes upon those of the
Professor. In an instant Volnow's muscles stiffened into immovable
rigidity, and he stood rooted to the deck powerless to move so much
as a finger.

"Captain Arnold," continued Natas, as though nothing had happened.
"We will rejoin our consorts, please, and release the aerostats in
accordance with the terms. This man's body will be returned in one of
them to his master, and the Professor here will write an account of
his death in order that it may not be believed that we have murdered
him. Konstantin Volnow, go into the saloon and write that letter, and
bring it to me when it is done."

Like an automaton the Professor turned and walked mechanically into
the deck-saloon. Meanwhile the _Ithuriel_ started on her way towards
the captive squadron. Before she reached it Volnow returned with a
sheet of paper in his hand filled with fresh writing, and signed with
his name.

Natas took it from him, read it, and then fixing his eyes on his
again, said--

"That will do. I give you back your will. Now, do you believe?"

The Professor's body was suddenly shaken with such a violent
trembling that he almost fell to the deck. Then he recovered himself
with a violent effort, and cried through his chattering teeth--

"Believe! How can I help it? Whoever and whatever you are, you are
well named the Master of the Terror."

CHAPTER XXX.

AT CLOSE QUARTERS.

As soon as the captive war-balloons had been released, the _Ithuriel_
and her consorts, without any further delay or concern for the issue
of the decisive battle which would probably prove to be the
death-struggle of the German Empire, headed away to the northward at
the utmost speed of the two smaller vessels. Their objective point
was Copenhagen, and the distance rather more than two hundred and
sixty miles in a straight line.

This was covered in under two hours and a half, and by noon they had
reached the Danish capital. In crossing the water from Stralsund they
had sighted several war-vessels, all flying British, German, or
Danish colours, and all making a northerly course like themselves.
They had not attempted to speak to any o