f
gas."

He pointed to a stream of tiny bubbles rising from the bottom of the
glass.

"Sea-water ain't it, sir?" said Edward respectfully; "but how did it get
up there?"

"Sea-water? no, my man. Beautifully clear, but strongly charged with
sulphur, magnesia, soda, and iron. Which spring did it come from?"

"That one which shoots out into the pool, sir," said one of the men.

"And is the other the same?" cried Jack.

"No, sir; cold as ice and quite fresh."

Jack and the doctor climbed up to see the sources of the two springs,
finding the hot not many yards from the edge of the rocky wall, where it
was bubbling up from a little basin fringed with soft pinky-white stone,
while the bottom of the pellucid source, which was too hot for the hand
to be plunged in, was ornamented with beautiful crystals of the purest
sulphur.

The source of the cold stream of fresh water they did not find, for it
came dancing down the dark ravine, which was choked with tree-ferns,
creepers, and interlacing boughs laden with the loveliest orchids, and
their progress was completely stopped when they had advanced some
hundred yards or so.

"The beginning of the curious features of the place," said Sir John as
they sat down to their pleasant meal, gazing through an arch of greenery
at the sapphire lagoon and the silver foam of the billows on the creamy
reef half-a-mile away.

Never did lunch taste more delicious to the rapidly invigorating boy,
never was water fresher, sweeter, and cooler than that of which he
partook. Then a good long hour's rest was taken as they all lay about
listening to the hum of insects, the whistle, twitter, and shrieking of
birds; and beneath it all, as it seemed, came the softened bass from the
reef.

"What do you say to a start back, Mr Bartlett?" said Sir John at last,
as he glanced at his son, who had just risen and gone knife in hand to
dislodge a cluster of lovely waxen, creamy orchids from a tree
overhanging the pool.

"I think we ought to be going soon, sir," said the mate.

"Here, Jack, my lad, what's the matter?" cried the doctor, springing up,
as he saw the lad holding the flowers he had cut at arm's length. "Ah!
stand still! Don't move whatever you do."

"Help, help!" shouted Edward. "Snakes! snakes!"

"Down flat, my lads, quick!" cried the mate; and as the men obeyed he
pointed out across the lagoon to where a great matting sail came gliding
into sight, looking misty and strange as se