start from a dream that he was being devoured by an immense water
snake.

He said nothing to the others about his night's adventure, for, as it
transpired, no one else had been awakened by his investigations. The
professor did not refer to his conversation with Mark.

"There's something queer going on aboard the ship this trip," said
Mark to himself. "But I guess it's none of my business. Professor
Henderson seems to know what he is doing and I guess I can trust him."

He resolved to think no more of the strange noises and movements, and,
for several nights thereafter he was not disturbed by them.

The weather, which, up to this time had been fair, took a sudden turn
for the worse about the fourth day after Mark's little night
expedition. One evening the sun sank in a mass of dull lead-colored
clouds and a sharp wind sprang up.

"We're going to have a storm," said Mr. Henderson. "It's liable to be
a bad one, too, from the way the barometer is falling."

He looked at the glass, and scanned the various instruments that told
how high up the Mermaid was and how fast she was traveling.

"We're pretty high up in the air," he said, "and scooting along at
about fifty miles an hour. We are going against the wind, too, but
fortunately it is not blowing hard."

At that moment there sounded from without a peculiar howling sound, as