r," was the answer. "I'm going to submerge."

A little later, by means of her diving rudders, aided also by the
tanks, the M. N. 1 began to sink. Down, down, down she went.

"Now I'll be able to show you some pretty sights, Mr. Hardley," said
Tom, as he and his friends entered the forward compartment, while the
steel shutters were rolled back from the heavy glass windows. "We'll be
in deep waters presently."

Ten minutes later the depth gauge showed that they were down about
three hundred feet, and that is pretty deep for a submarine. But Tom's
boat was capable of even greater depths than that.

At first there was nothing much to observe save the opal-tinted water
illuminated by the powerful lights of the submarine. Small, and
evidently frightened, fish darted to and fro, but there was nothing
especially to attract the attention of Tom and his friends, who had
made much more sensational trips than this under water.

Mr. Hardley, however, was fascinated, and kept close to the observation
windows.

"Are there any wrecks around here?" he asked Tom.

"Possibly," was the answer. "Though they do not contain any treasure, I
imagine--brick schooners or cargo boats would be about all."

The submarine went deeper, plowing her way through the Atlantic at a
depth of more than three hundred and fifty feet, for Tom wanted to
subject her to a good test.

Suddenly Mr. Hardley, who was now alone at the window on the port side,
uttered a cry of alarm.

"Look! Look!" he fairly shouted. "We're surrounded by a school of
sharks! What monsters! Are we in danger?"

CHAPTER XIII

THE SEA MONSTER

Tom Swift, who had been making readings of the various gauges, taking
notes for future use, and otherwise busying himself about the
navigation of his reconstructed craft, turned quickly from the
instrument board at the cry from Mr. Hardley. The gold-seeker, with a
look of terror on his face, had recoiled from the observation windows.

"Bless my hat band!" cried Mr. Damon. "Look, Tom!"

They all turned their attention to the glass, and through the plates
could be seen a school of giant fishes that seemed to be swimming in
front of the submarine, keeping pace with it as though waiting for a
chance to enter.

"Are we well protected against sharks, Mr. Swift?" demanded the
adventurer. "Are these sea monsters likely to break, the glass and get
in at us?"

"Indeed not!" laughed Tom. "There is absolutely no danger from these
fis