r the reef, and so, when he saw a
beautiful pearly-white shell lying at the bottom of the water, which was
not more than five feet deep under any part of the natural arch of soft
porous stone, he threw off his clothes and unhesitatingly made a dive
for it.

He got the shell, and made a very important discovery at one and the
same time. Happening to glance upward as he came to the surface, his
quick eye saw a low, narrow opening leading directly into what seemed to
be the solid rock.

The mouth of the cavern was slightly shelving, and situated a little
less than mid-way of the centre of the arch.

Frank lost no time in climbing into it, and was surprised to find
himself in a semi-dark, sea-scented cavern, in shape something like an
old-fashioned Dutch oven and fully seven feet in height.

There was sufficient light to enable him to see that the floor of the
cave was thickly strewn with fragments of shells and gray-white coral,
the stone itself being so soft that he could easily penetrate it with
his jack-knife.

These submarine caves or grottos are numerous in the Bermudas, and the
limestone rock of which they are mainly formed so extremely
impressionable as to be readily cut into blocks for building purposes
with a common saw.

Frank remembered having heard Captain Thorne speak of them, but he
little thought at the time that he would ever be the discoverer of one
on an island in the midst of the Caribbean Sea.

Solitude, and having to look out for himself, as the saying goes, if it
had done nothing else, had sharpened his wits, and he was not long in
coming to the conclusion that, by enlarging the cave inland, he could
make an opening quite near his tent, and thus have both a dry and
wet-weather habitation.

He returned to the beach, where the Sea Eagle was daily sinking deeper
and deeper in the sand, full of his new plans. He could hardly prepare
his supper, so eager was he to begin work on his latest project and have
his stores securely housed before the rainy season set in.

He went to bed early, but was up with the dawn, ate his breakfast while
yet the rays of the rising sun were but faintly illumining the east, and
then, with hatchet and hammer and saw, some coils of stout rope and a
plentiful supply of food, set out for the cave.

He was not long in reaching it, and by noon had cut through five feet of
the calcareous stone, piling up the portion cut away in a kind of wall
on the lower side, where the