ay went the boys with a tremendous rush, making the water foam, and
naturally the biggest and strongest took the lead, leaving three little
fellows well behind.

The doctor had anticipated this, and drew their attention with a shout,
at the same time holding up another shilling, and as they turned to swim
back, he suddenly dropped the coin about six feet away from the yacht's
side, where the water was still.

_Plop_! down went one little fellow, who rose up, turned over, sent his
heels gleaming in the sunshine, and disappeared, as _plop! plop_! down
went the two others.

"Just like a lot of dabchicks," cried the doctor; "now we shall see them
race for it. See the shilling, Jack?"

"Yes; here it goes."

"Yes, and here they come. Look at them. Why, they go down faster than
the coin. It's wonderful."

Wonderful it was, for the dark little figures glided through the crystal
water like seals, and every motion could be followed till the coin was
reached and ceased to twinkle as it sank. Then once more the dark
figures grew plainer and rose and rose, but somehow more and more
astern, and Jack looked startled.

"Why, there must be a tremendous current here," he cried. "They're
being swept away. A boat! a boat!"

The doctor looked as much startled as his companion, but a very gentle
vibration enlightened them the next moment, for the engine was once more
in motion, the screw revolving slowly, and the _Silver Star's_ prow was
gradually coming round in answer to the helm, till she pointed straight
for the open sea, where the throbbing and quivering of the vessel
increased as she went easily ahead, and then faster still over the
perfectly calm water, for there was not a breath of air.

Then away and away through the burning sunshine the yacht glided, with
the sea glistening like damascened steel frosted with silver, till the
mountains above the coaling port grew distant; and away over the burning
Afric sands there was a wondrous orange glow which deepened into fire,
vermilion, crimson, purple, and gold of the most refulgent hues, and
soon after it was night. It seemed to Jack as he stood gazing forward
that they were gliding on between two vast purply black basins studded
with stars, which were larger and brighter than any he had seen before,
while deeper and deeper in the wondrous depths there were more and more,
till the farthest off seemed like clusters and patches of frosted gold.

There was not a breath of