ound the whistle if necessary. I don't
know that there will be any occasion for it, but if, for any reason, you
should want to call us, you can give three blasts upon the whistle, and
we will act accordingly."

During this time the boys had been silently taking their positions in
the small boat; Tom, by direction of the professor, in the bow, while Jo
and Berwick took the oars.

"You need to keep a sharp lookout ahead," advised the professor when
they started. "We are liable to run into almost anything, and we don't
want to be caught unawares."

"All right," responded Tom. "I've got my eyes and ears wide open."

As silently as a spectral boat, the little craft slipped through the
darkness, the rowers dipping their oars almost without a creak or jar.
Nevertheless they advanced rapidly toward the shore that loomed up grim
and forbidden like a wall of impenetrable darkness.

It was but a few minutes before the boat was run up on the beach at the
foot of the cliffs and the party disembarked. The boat was then carried
a sufficient distance on to the shore and hidden in the heavy
underbrush.

"Now, boys," began the professor when they had completed their
preparations, "you are our scouts and we have to depend upon you to
thwart our enemies, if they are about. Tom, you had better take the
lead, and Jo will cover the rear. Instead of the long way around that
you took when you last sought the smoke signal, I think we will adopt
the direct and more rugged climb, as less liable to ambush. When you are
ready, go ahead."

Without making any reply, Tom, with his rifle in his hand ready for
immediate use, slipped away among the bushes. Berwick followed, then the
professor and Jo last. It was light enough at this time for Tom to make
his way among the rocks, which at this point were piled up in great
masses, covering the ground just as they had fallen from the cliffs
above.

There was a semblance of a path or way through the rocky defile which
led with many turns and twists along the course of what, in the wet
season was apparently the bed of a stream, but although this roadway was
less difficult to negotiate, Tom ignored it and kept to the more rugged
way, skirting the bed of the water course.

Pushing on energetically, Tom opened up a gap between himself and the
others for whom the professor set the pace, a less rapid one. Glancing
ahead they saw that Tom had halted and was signaling for a cautious
advance.

A little fa