ubmarine began to bubble
as the missiles from the machine guns cut the waves.

"Maybe it's an English vessel sent to capture Mark and me because of
that anarchist trouble at the hotel," Jack went on.

"Nonsense!" exclaimed the captain. "But whatever it is, we must stop it,
or they will sink my ship. Wave your handkerchief, Jack."

The boy sprang to the top of the conning tower, in order to permit those
on the vessel to see him more plainly, and vigorously shook the white
rag. That it was observed was evident when some one on the steamer
wig-wagged back a reply. In a few minutes a boat was seen to put off
from the ship, and soon a little launch, in command of a lieutenant in
uniform, drew up alongside the _Porpoise_.

"Who is captain of this craft?" asked the lieutenant as he came aboard.

"I am," replied Mr. Henderson. "What do you mean by firing on me?"

"I am Lieutenant Muchmore," said the other, saluting. "Captain Wackford,
of the _Sylph_, in His Britannic Majesty's service, presents his
compliments, and asks you to pardon the occurrence. You see we took you
for a derelict and were trying to sink you."

"I thought perhaps war had broken out between some country and the
United States since we left port," went on Mr. Henderson, "and that you
were trying to make a capture."

"No, it was only that we thought you a waterlogged craft, and a danger
to navigation," repeated the lieutenant. "But what sort of a ship have
you?"

"Come below and I'll show you the finest submarine that ever was built,"
answered the inventor with pardonable pride. "If you don't mind, give
your launch orders to go back to the ship, and I'll show something that
will make you open your eyes."

Anxious to see what the strange little craft could do Lieutenant
Muchmore sent his launch back, and went below with Captain Henderson. He
was astonished at what he saw, and unlike most Englishmen was willing to
say so.

Mr. Henderson then went to the conning tower. He directed the man-hole
cover to be clamped on, and then filled the tanks. The ship sank fifty
feet below the surface and then shot forward.

Seated in the cabin the lieutenant was observing with wonder showing on
his face at the accomplishment of sailing along under water. Suddenly
the lights were shut off, and the shutters moved back from the
bull's-eye windows. The sea, glowing in the beams of the search light,
was alive with fish, large and small, beautiful and hideous.

"Wonderf