highest summit in the whole island. Although it was very far below us, we could see it quite plainly; and it looked wobbly enough to be pushed off its perch with the hand. There was a legend among the people, they said, that when the greatest of all Popsipetel kings should be crowned in the ivory chair, this hanging stone would tumble into the volcano's mouth and go straight down to the centre of the earth.
The Doctor said he would like to go and examine it closer.
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
