And so the afternoon wore on.

"We shall be no sooner," said Jack at last. "In an hour it will be
dark."

"Yes," said the doctor with a sigh. "It would not matter if the blacks
are not there first, but the worst of it is, as soon as it's dusk the
captain will be lighting up that firework business for a beacon, and
that will show the canoes where to steer."

It proved just as he said. The darkness came on with awful rapidity as
soon as the sun disappeared beneath the waves, all searching the edge of
the reef most anxiously during the last rays which flooded the sea; but
in vain; and then for a full hour they rowed steadily on, guided by the
gleaming of the fireflies against the black darkness ashore, but all at
once a bright star shone out.

"There she is!" cried Jack excitedly. "Look how Mr Bartlett has turned
the boat's head straight for the light."

"Yes; we shall follow the bright path straight away now," said the
doctor.

"How are you getting on there?" came from the boat in front. "Hungry,
or will you wait till we get on board?"

"We'll wait, father," shouted Jack.

"Yes. Only half-an-hour now. Mr Bartlett thinks we've distanced the
canoes."

They were soon to learn for certain, as they followed the bright path of
light which minute by minute grew clearer, till they could see as it
were right up to the anchored yacht.

"Shall we hail the captain?" said Jack.

He had hardly spoken when he felt a jar run through the boat, and found
that the towing-line had been hauled upon till the prow of the second
boat touched the stern of the first.

"Hist there!" said the mate. "Perfect silence, please. We must creep
alongside so as to give warning. There must be no hailing. This is the
most dangerous time."

"How far are we away?" said the doctor in a whisper.

"About five hundred yards."

"How is it the oars go so quietly now?" whispered Jack.

"Muffled, and the men are just dipping them, so as to keep a fair way
on."

The next two or three minutes were passed in silence, Jack's boat having
once more dropped astern to the full length of the rope.

The lad had risen to stand up and watch the line of light extending from
them right up to the source of the rays ahead, and from his position he
could look right over the foremost boat.

"How deceptive it is!" he thought. "One can hardly tell how near we
are, and--ah!--"

"What is it, boy?" whispered the doctor.

For answer Jack pointed righ