"Now," continued the teacher, leading his pupil to the side of the
barge, "be sure to go down slow, and come up slow. Whatever you do, do
it slow, for if you do it fast--especially in comin' up--you'll come to
grief. If a man comes up too fast from deep water, the condensed air
inside of him is apt to swell him out, and the brain bein' relieved too
suddenly from the pressure, there's a rush of blood to it, and a singin'
in the ears, and a pain in the head, with other unpleasant symptoms.
Why," continued Baldwin, growing energetic, "I've actually known a man
killed outright by bein' pulled up too quick from a depth of twenty
fathoms. So mark my words, lad, and take it easy. If you get nervous,
just stop a bit an' amuse yourself with thinkin' over what I've told
you, and then go on with your descent."

At this point Rooney's heart almost failed him, but, catching sight of
Maxwell's half-amused, half-contemptuous face, he stepped resolutely on
the ladder, and began to descend in haste.

"Hold on!" roared Baldwin, laying hold of the life-line. "Why, man
alive, you're off without the front-glass!"

"Och! Whirra! So I am," said Rooney, pausing.

"Pump away, lads," cried Baldwin, looking back at his assistants.

"Whist! What's that?" asked the pupil excitedly, as a hissing sound
buzzed round his head.

"Why, that's the air coming in. Now then, I'll screw on the glass. Are
you all right?"

"All right," replied Rooney, telling, as he said himself afterwards,
"one of the biggist lies he iver towld in his life!"

The glass was screwed on, and the learner was effectually cut off from
all connection with the outer air, save through the slight medium of an
india-rubber pipe.

Having thus screwed him up--or in--Baldwin gave him the patronising pat
on the helmet, as a signal for him to descend, but Rooney stood tightly
fixed to the ladder, and motionless.

Again Baldwin patted his head encouragingly, but still Rooney stood as
motionless as one of the iron-clad warriors in the Tower of London. The
fact was, his courage had totally failed him. He was ashamed to come
up, and could not by any effort of will force himself to go down.

"Why, what's wrong?" demanded Baldwin, looking in at the glass, which,
however, was so clouded with the inmate's breath that he could only be
seen dimly. It was evident that Rooney was speaking in an excited
voice, but no sound was audible through that impervious mass of metal
and