human head, in order that the wearer may have room to move his
head freely about inside of it. It should not touch the head in any
part, but is fixed rigidly to the breast-plate, resting on the
shoulders, and does not partake of the motions of the head. In it are
three round openings filled with the thickest plate-glass and protected
by brass bars or guards; also an outlet-valve to allow the foul air to
escape; a short metal tube with an inlet-valve, to which the air-pump is
screwed; and a regulating cock for getting rid of excess of air. The
arrangement is such, that the fresh air enters, and is spread over the
front of the diver's face, while the foul escapes at the back of his
head. By a clever contrivance--a segmental screw--the helmet can be
fixed to its neck with one-eighth of a turn, instead of having to be
twisted round several times. To various hooks and studs on the helmet
and breast-plate are hung two leaden masses weighing about forty pounds
each.

These weights having been attached, and a waist-belt with a knife in it
put round Rooney's waist, along with the life-line, the air-tube was
affixed, and he was asked by Baldwin how he felt.

"A trifle heavy," replied the pupil, through the front hole of the
helmet, which was not yet closed.

"That feeling will go off entirely when you're under water," said
Baldwin. "Now, remember, if you want more air, just give two pulls on
the air-pipe--an' don't pull as if you was tryin' to haul down the
barge; we'll be sure to feel you. Be gentle and quiet, whatever ye do.
Gettin' flurried never does any good whatever. D'ee hear?"

"Yis, sur," answered Rooney, and his voice sounded metallic and hollow,
even to those outside--much more so to himself!

"Well, then, if we give you too much air, you've only got to open the
front-valve--so, and, when you're easy, shut it. When you get down to
the bottom, give one--only one--pull on the life-line, which means `All
right,' and I'll give one pull in reply. We must always reply to each
other, d'ee see? because if you don't answer, of course we'll think
you've been suffocated, or entangled at the bottom among wreckage and
what-not, or been took with a fit, an' we'll haul you up, as hard as we
can; so you'll have to be particular. D'ee understand?"

Again the learner replied "Yis, sur," but less confidently than before,
for Baldwin's cautions, although meant to have an encouraging effect,
proved rather to be alarming.