more boisterous, and the Professor
suggested that the jib be taken down, which was done; but the increasing
gale, and the terrible strain on the mast and sail, made the boys look
inquiringly at the Professor, for a word of warning.

He sat there grimly during the raging storm, and with the halliards
gradually let down the mainsail when the tempest had reached such a
point that it appeared to sweep everything from the boat.

Where was Angel during all this uproar? Forward in the housed portion of
the boat, curled up in a corner, and apparently unconscious, the little
creature did not seem at all perturbed.

"Don't you think he is seasick?"

"It is not likely. Seasickness is akin, you know, to that dizzy feeling
some people have when at a height. The natural instincts of the animal
prevent him from having any feeling of discomfort at a height. The trees
are their homes, and for that reason they can swing from branch to
branch and sway back and forth in the loftiest trees without an
uncomfortable feeling."

The heavy blow continued until they had reached the cliffs, when it
abated somewhat, and the boys anxiously inquired whether it would be
safe to make the entrance to the river during the gale.

"We are out for the purpose of testing the boat. To make an attempt to
round the cliff and steer it into the mouth of the river in this wind
will be the best test of its maneuvering ability."

As stated, the wind was now blowing from the southwest, and they were
northeast of the mouth of the stream they wished to enter. They stood
out to sea in order to make a starboard tack, and it was a gratification
to see the magnificent manner in which the vessel responded, and before
six o'clock they found themselves sailing up the river, and safely
landed at the boathouse.

An examination showed that the crossbeam supporting the mainmast was
split from end to end, and only the roof structure held it in place.
Thus the trip had a warning lesson for them, and Harry was not slow to
take advantage of it and install a larger crosspiece.

George had entirely forgotten the incident of the calcareous slab which
had on it the tracings of the cave, and which had been the means of
giving the Professor the first hint that they were in a pirate's cave.

The first thing in the morning he went over to the laboratory, and
called attention to the slab. "Here it is," said the Professor. "You
will note that the light shows some characters which ca