e finished his preparations by laying out
the rope in rings and curves of various shapes, such as would easily run
out. "I say, you are perfectly black when I look at you from behind,
but in front you seem like a white image on a black ground. Now, then,
what do you mean to do?"

"Dive in from here and try to keep right down and swim as deeply as I
can for the mouth."

"Try to swallow the job at one mouthful?"

"Yes."

"Won't do," said the middy, authoritatively. "You couldn't do it. You
must slip in gently here and swim to that rock that's just out of the
water."

"What! That one that seems just to the left of the arch?"

"That's the one. Get out on it, wait a few moments, and then take a
long, deep breath and dive."

Aleck pondered for a few moments.

"Yes," he said, "I think you're right. I should have had to swim so far
first if I started from here."

"To be sure you would. The less diving you have the better."

"I see," said Aleck. "Now, then, let the rope run out easily through
your fingers till I give it a sharp jerk. That means pull me back as
fast as you can."

"Yes, because you can go no further."

"If I pull twice it means I am safe through, and then--"

"I shall tie my end of the rope round my chest and come too. You need
not pull, only just draw in the line, unless it stops, because that
would mean I had got into difficulties. Do we both understand? I do."

"So do I," said Aleck, "so let's get it over. If I wait much longer I
shall be afraid to go."

"Don't believe you," said the middy, bluntly. "Now, then--ready?"

"Yes."

The word was no sooner uttered than Aleck slipped down into the water
and began to swim, with the rope being carefully paid out by his
comrade, and in a minute he was fairly started. He was at first
invisible, but very soon began to look like a black object making its
way over a surface that grew transparent.

Then all at once the rope ceased to run.

"What is it?" cried the middy, anxiously.

"Got to the rock."

"Is the water deep?"

"Very."

"Well, get up, ready for your dive."

"It's all seaweed, and horribly slippery."

"Never mind; up with you."

A peculiar splashing sound arose, and the middy could just make out the
dim shape of his companion climbing, or rather dragging, himself on to
the slimy rock, whose top was about a foot above the surface of the
water.

"Stop a minute or two first," said the middy, "so as to take--"

He