"It's splendid; but I wish it was a bit lighter.

There must be somewhere for the light to come in.

Yes, I see!" Vince pointed up at the side farthest from him where he stood, and a little closer investigation showed that the pale soft light appeared to be reflected upward against the roof, coming from behind a screen of rock.
Crossing to this spot, they found that they could pass round the rocky screen, which reached half-way to the ceiling, and they now stood in a narrow passage lit by a soft green light, which came through a low arch, and on reaching and passing through this the boys uttered a shout of delight, for before them was another cavern of ample dimensions, whose low flattened roof was glorious with a lovely, ever-changing pattern, formed by the reflection of the sunlight from the waves outside.

They were fascinated for the time by the appearance of the roof, which seemed to be all in motion--lights and shadows, soft as silken weavings, chasing each other, opening, closing, and interlacing in the most wonderful way, till they grew dazzled.
"It's too much to see at one time," whispered Mike at last.

"I say! look at the arch with ferns hanging all round like lace." "Yes, and what a colour the sea is!" "And the anemones and limpets and coral! Look at those pools, too, among the rocks." "Yes, and outside at the sea-birds.