Perhaps Josh felt quite confident, but no one else did, as the water rose and fell, giving lovely little views of sea and sky, and then turned into veils of crystal, green and blue, sparkling sometimes like emerald, then changing to amethystine or sapphire hue.
It was surprising what an amount of light seemed to come in when the water sank, and then by contrast the darkness was horrible, and the lanthorn seemed to emit a dismal yellow glow.
They might have stayed for another quarter of an hour watching the light come and go, but there was the danger of their being inclosed in some portion of the cavern where the roof was low, and the boat would be made a prisoner within a prison. So Josh urged the boat forward towards where Mr Temple had been so busy with his researches, and after a little examination he bade Will cover the lanthorn with his jacket.
“It’s a long time since I were in here,” he said; “but I think as the air-hole ought to be somewhere about here. One moment, Will, lad; hold the light up and lets see the roof.”
The rocky summit was in the highest part, some twelve feet above their heads, and satisfied as to this, Josh had the light darkened, and then began to look upward.
“No,” he said. “Must be the next. Show the light.”
He thrust the boat along once more, grinding and bumping over fragments of rock, till they had passed under another low part of the roof, when this rose once more, and the lanthorn being hidden Josh pointed upward to a narrow crack, through which came a faint light.
“There y’are,” he said. “Don’t matter how high the water gets, we can get plenty of fresh air. Tide won’t get up there.”
The position seemed more hopeful now, for the tide would have to rise fourteen or fifteen feet to carry them to the roof; and though in certain places from low water to high water might be perhaps forty feet, they were now so near the height of the tide that it was not likely to rise much farther.
“Don’t be frightened, Taff, old chap,” said Dick in a whisper; “father’s with us, and he’ll mind that we don’t get hurt.”