unusual," they said. "But the explanation is quite simple.
It used to be a mountainous part of South America--an overhanging
part--sort of an awkward corner, you might say. Way back in the glacial
days, thousands of years ago, it broke off from the mainland; and by
some curious accident the inside of it, which is hollow, got filled with
air as it fell into the ocean. You can only see less than half of
the island: the bigger half is under water. And in the middle of it,
underneath, is a huge rock air-chamber, running right up inside the
mountains. And that's what keeps it floating."

"What a pecurious phenometer!" said Bumpo.

"It is indeed," said the Doctor. "I must make a note of that." And out
came the everlasting note-book.

The porpoises went bounding off towards the icebergs. And not long
after, we saw the sea heaving and frothing as a big herd of whales came
towards us at full speed.

They certainly were enormous creatures; and there must have been a good
two hundred of them.

"Here they are," said the porpoises, poking their heads out of the
water.

"Good!" said the Doctor. "Now just explain to them, will you please?
that this is a very serious matter for all the living creatures in this
land. And ask them if they will be so good as to go down to the far
end of the island, put their noses against it and push it back near the
coast of Southern Brazil."

The porpoises evidently succeeded in persuading the whales to do as
the Doctor asked; for presently we saw them thrashing through the seas,
going off towards the south end of the island.

Then we lay down upon the beach and waited.

After about an hour the Doctor got up and threw a stick into the water.
For a while this floated motionless. But soon we saw it begin to move
gently down the coast.

"Ah!" said the Doctor, "see that?--The island is going North at last.
Thank goodness!"

Faster and faster we left the stick behind; and smaller and dimmer grew
the icebergs on the skyline.

The Doctor took out his watch, threw more sticks into the water and made
a rapid calculation.

"Humph!--Fourteen and a half knots an hour," he murmured--"A very nice
speed. It should take us about five days to get back near Brazil. Well,
that's that--Quite a load off my mind. I declare I feel warmer already.
Let's go and get something to eat."

THE FIFTH CHAPTER. WAR!

ON our way back to the village the Doctor began discussing natural
history with Long Arrow.