and tossing under the influence of a ground swell, became more
steady and quiet once it left the surface.

The searchlight in the conning tower was turned on, and in the glare of
it Andy and the professor were able to steer properly, aided by the
compass which gave them the true southern course.

It was now quite dark. Additional electric lights were switched on in
the cabin, engine and dining room. Andy came out of the conning tower
and announced that Captain Henderson wanted Washington to get supper.

All the cooking was done by electricity, and, in addition to a supply of
the usual and ordinary kinds of food, there was a big lot of patent
condensed victuals to draw on. Soup, broiled steak, potatoes, hot
biscuits, rice pudding and coffee made up the repast which was enjoyed
by all.

Toward the close of the meal Professor Henderson began to sniff the air
of the cabin.

"What's the matter? Do you smell a storm brewing?" asked Andy.

"No, but the air is not as fresh as it should be," replied the inventor.
"Washington, release a little more of the supply from the compression
tanks."

The ship, which had been left to steer itself automatically while the
professor was absent from the conning tower, was moving along at about
half speed. The gage showed they were going at twenty miles an hour, and
were three hundred feet below the surface.

"Washington and I will share the first night's watch between us," said
the inventor, after the supper things had been cleared away. "There will
not be much to do, as the ship will steer automatically in whatever
direction I set her. Still I want to see how she behaves. The rest of
you might as well go to your bunks."

The two boys were especially glad of a chance to go to bed, as they had
had but little sleep the night before on account of the fire. So they
lost no time in undressing and rolling up in the blankets, for it was
quite cool so far down under the water.

"Well, we've slept on the earth, above the earth and now we're under the
waters," observed Jack.

"There's only one place more to spend your time taking a snooze," said
Mark.

"Where's that?"

"Inside the earth."

Then they fell asleep. During the night and the next day the _Porpoise_
forged on underneath the waves. Washington relieved Mr. Henderson in the
conning tower and reported the machinery to be working well.

"Keep her headed due south," was the order of the inventor, and the
colored man did so.