And when we were come to the lip of the volcano (it took us half a day to get up to it) we found the stone was unbelievably large—big as a cathedral. Underneath it we could look right down into a black hole which seemed to have no bottom. The Doctor explained to us that volcanoes sometimes spurted up fire from these holes in their tops; but that those on floating islands were always cold and dead.
“Stubbins,” he said, looking up at the great stone towering above us, “do you know what would most likely happen if that boulder should fall in?”
“No,” said I, “what?”
“You remember the air-chamber which the porpoises told us lies under the centre of the island?”
“Yes.”
“Well, this stone is heavy enough, if it fell into the volcano, to break through into that air-chamber from above. And once it did, the air would escape and the floating island would float no more. It would sink.”
“But then everybody on it would be drowned, wouldn’t they?” said Bumpo.
“Oh no, not necessarily. That would depend on the depth of the sea where the sinking took place. The island might touch bottom when it had only gone down, say, a hundred feet. But there would be lots of it still sticking up above the water then, wouldn’t there?”
“Yes,” said Bumpo, “I suppose there would. Well, let us hope that the ponderous fragment does not lose its equilibriosity, for I don’t believe it would stop at the centre of the earth—more likely it would fall right through the world and come out the other side.”
Many other wonders there were which these men showed us in the central regions of their island. But I have not time or space to tell you of them now.