ick," said Tom, after a painful pause. "No
use of going on without him."

"I hope he hasn't fallen over some cliff and hurt himself," returned his
younger brother.

"I don't see why he doesn't answer us, if he's all right," was the
unsatisfactory reply. "Come on, or the storm will overtake us before we
get down from the mountain and we'll be soaked by the time we reach
home."

Side by side the brothers retraced their steps--a hard task, for it is
much easier to climb down a steep mountainside than to climb up.

To those who have read the previous volumes in this "Rover Boys Series,"
the two brothers just mentioned will need no special introduction. The
Rover boys were three in number, Dick being the oldest, fun-loving Tom
coming next, and Sam bringing up the rear. All were bright, lively,
up-to-date lads, and honest and manly to the core. They lived on a farm
called Valley Brook, in New York state,--a beautiful spot owned by their
uncle, Randolph Rover, and his wife, Martha. Their father, Anderson
Rover, also lived at the farm when at home, but he was away a great deal
on business.

From the farm the boys had been sent, some years before, to Putnam Hall,
an ideal place of learning, of which we shall learn more as our tale
proceeds. What the lads did there on their arrival has already been
related in "The Rover Boys at School," the first volume of this series.

A short term at Putnam Hall was followed by a trip on the ocean, and
then a long journey to the jungles of Africa, in search of Anderson
Rover, who had disappeared. Then came a grand outing out west, and
another outing on the great lakes, followed by some stirring adventures
in the mountains of New York state.

Coming from the mountains, the three youths had expected to go back to
Putnam Hall at once, but fate ordained otherwise and they were cast away
in the Pacific Ocean, as related in "The Rover Boys on Land and Sea."
They had a hard task of it getting home, and then returned to the school
and had some splendid times while in camp with the other cadets.

When vacation was once more at hand the boys soon solved the problem of
what to do. Their Uncle Randolph had taken a houseboat for debt. The
craft was located on the Ohio River, and it was resolved to make a trip
down the Mississippi.

"It will be the best ever!" Tom declared, and they started with much
enthusiasm, taking with them "Songbird" Powell, a school chum addicted
to the making of doggerel w