a cherub in the sky!" said Jess.

"Why is it blue though?" asked Lorna.

"Because of the refraction of light," explained Mrs. Beverley from the
next boat. "We see a kind of concentrated reflection of the sky sent to
us under the sea. If it were a gray day outside it would be gray in here
too. Some people think that the Mediterranean has risen, and that once
the water in this grotto was much lower, so that boats could sail in and
out of it quite easily. Do you see that landing-place over there? It
leads to some broken steps and a blocked-up passage that tradition says
wound up through the cliff right to the villa of Tiberius. Perhaps it
was a secret way by which he thought he might escape if danger
threatened him."

"How I'd love to explore it," sighed Irene.

"It only goes a little way before it is blocked. It's hardly worth
landing to look at it. Be careful, Renie! If you lean over the edge of
the boat so far you'll be upsetting us, and, although we might look very
delightful and silvery objects under the water, I'm not at all anxious
to offer myself for the experiment."

"Why don't they enlarge the entrance?" asked Vincent.

"Because nobody is sure whether by doing so they might or might not
spoil the beautiful effect of blue light in the grotto. It's too risky a
venture to try. Besides in present conditions the boatmen make a great
deal of money by taking tourists into the grotto. If it were very easy
to get in they could not charge so much. It's a little mine of wealth to
the Capri fisherfolk now, though years ago they used to say the place
was haunted, and tell terrible tales about it. They said fire and smoke
had been seen issuing from the entrance, that creatures like crocodiles
crept in and out, that every day the opening expanded and contracted
seven times, that at night the Sirens sang sweetly there, that any young
fishermen who ventured to sail near disappeared and were never seen
again, and that the place was full of human bones."

"What a gruesome record," declared Vincent. "I agree with Renie though,
I'd like to explore that passage with a strong bicycle lamp, or an
electric torch. Who knows what we might find if we looked about--a coin
that Tiberius had dropped out of his pocket, or one of the Sirens'
hairpins, or a crocodile's tooth at least. Yes, I must positively come
again, Mater. Just to prove the truth of your stories."

"Silly boy," laughed his mother. "I expect every stone of the place has