aited impatiently for their return, grumbling at not being allowed
to go with them, for the sea was as smooth as a mountain lake, and the
water so clear that the smallest pebble could be discerned lying upon
the white sandy bottom five fathoms below.

Said Will presently, 'I don't believe there's a shark within a mile; do
you?'

'No,' I answered, looking longingly at the crystal water and then at the
black mouth of the cavern, which neither Will nor I had ever entered.

'Then come on,' said Will, quickly, and in a few seconds we were out of
our clothes, and paying no heed to 'King Billy's' exclamations of terror
we dropped quietly into the water and swam across, telling him to stay
where he was and keep a look-out for sharks.

A few strokes brought us safely over, and then, as we climbed up and
stood on the cold rocky floor of the dark cave, our hearts began to fail
us somewhat--the place was so grim, silent and terrifying.

Feeling our way carefully along, however, we advanced for some ten or
twelve yards and then stopped, for though we heard the voices, we could
see the figures of Harry and Trenfield but dimly.

'Where are you?' cried Will.

'Over here,' answered my brother; 'you can come along if you like. We
think that there's a way of getting out by climbing up--we can see the
trees on the back of the hill.'

This was a discovery indeed, and Will and I, as we made our way to
where they sat, found the darkness decreasing at every step, and when
we reached them, we could see about us quite plainly, for thin, dimmed
shafts of sunlight penetrated the cavern from above by a narrow cleft,
through which we could see not only the dark foliage of the trees, whose
branches overhung the place, but a strip of blue sky.

'Listen!' said Will.

Somewhere near a 'butcher' bird was calling to its mate, who quickly
answered, and then the pair whistled sweetly and joyously together;
and when they ceased a bell-bird sounded his clear, resonant note
thrice--then silence.

Presently Walter and Harry set about to attempt an ascent, laughing
heartily at the thought of how we should startle poor 'King Billy' by
reappearing out of the bowels of the earth, instead of by the way we had
left him.

The top of the cleft was not more than thirty feet from the floor of the
cave, and its very narrowness reduced the difficulty of climbing up its
rugged sides, which were composed of pieces of rock embedded in earth.
In the centre, howe