ntinued, and Mark and Jack ran to do
this.

In a few minutes the line was stretched into the engine room, and water
was being thrown on the flames, for Washington had started the pump as
soon as he saw the conflagration.

The fire was in one corner, near the electrical switch board, and had
been caused by the blowing out of one of the fuses, which occasioned the
little explosion. The wood work near the switches was blazing fiercely,
and soon the ship was filled with smoke.

"Empty the ballast tanks!" called the professor. "We must rise to the
surface!"

"We'll all be burned up!" cried Tom. "First we nearly smother and then
we get on fire. Neber saw such luck!"

With a rush the _Porpoise_ began to rise, as her tanks were lightened.
With steady hands, though with fear in their hearts, Jack and Mark
continued to play the water on the flames, while the professor and
Washington got out a second line and aided them.

"The fire is dying out!" exclaimed Mr. Henderson. "We'll soon get the
best of it."

In five minutes the worst was over, though it had been an anxious time,
and one of danger. The ship came to the surface, and the open man-hole
let out the thick smoke that had nearly suffocated the travelers.

As soon as it was cool enough in the engine room an examination was made
of the damage done. It was not as bad as the professor had feared, and
the running part of the ship was not harmed. A new fuse was put in and
the electric lights turned on.

The night was spent with the ship floating on the surface of the ocean,
only enough speed being kept up to give her steerage way. The professor
did not want to go below the waves until he had repaired the switch
board.

Watch was kept, for, though they were out of the regular line of ocean
travel, there was no telling when a vessel might come along and run
them down, for the _Porpoise_ did not show above the waves more than a
few feet, and carried no lights.

Mark had the watch just after midnight, and was sitting in the conning
tower, the door of which opened out on the small deck. He had swept the
surface of the water with powerful glasses and was sure there were no
ships in sight. So, feeling that he would like to stretch his legs, he
walked up and down on the platform.

He had reached the after end, and was about to turn and go back, when he
was startled to see between him and the conning tower a white object. At
first Mark thought it was a cloud of mist, or some