er
the shape or design of the helmet or dress, Siebe's principle is the
one in universal use to-day.

The metal tabs are for carrying the diver's lead weights, which are
fitted with suitable clips; the hooks--one on each side of the
helmet--are for keeping the ropes attached to the back weight in
position. The helmet and breastplate are fitted at their lower and
upper parts respectively with gun-metal segmental neck rings, which
make it possible to connect these two main parts together by
one-eighth of a turn, a catch at the back of the helmet preventing any
chance of unscrewing. The small eyes at the top of the helmet are for
securing the diver's air pipe and life line in position and preventing
them from swaying.

[Illustration:

Front view of Helmet.

A, Helmet.
B, Breastplate.
F, Emergency cock.
G, Glasses in frames.
H, Metal screws and bands.
I, Metal tabs.
J, Hooks for keeping weight ropes in position.
L, Eyes to which air pipe and life line are secured.

Side sectional view of Helmet.

K, Segmental neck rings.
D, Air conduits.
M, Telephone receiver.
N, Transmitter.
O, Contact piece to ring bell.

Back view of Helmet.

Plan of Helmet.
C, Air inlet valve.
E, Regulating outlet valve.
G, Glasses in frames.
L, Eyes to which air pipe and life line are secured.
P, Connexion for telephone cable.

FIG. 3.]

The _Diving Dress_ is a combination suit which envelops the whole body
from feet to neck. It is made of two layers of tanned twill with pure
rubber between, and is fitted at the neck with a vulcanized
india-rubber collar, or band, with holes punched in it corresponding
to the screws in the breastplate. This collar, when clamped tightly
between the bands and the breastplate by means of the nuts, ensures a
watertight joint. The sleeves of the dress are fitted with vulcanized
india-rubber cuffs, which, fitting tightly round the diver's wrists,
prevent the ingress of water at these parts also.

_Boots._--These are generally made with leather uppers, beechwood
inner soles and leaden outer soles, the latter being secured to the
others by copper rivets. Heavy leather straps with brass buckles
secure the boot to the foot. Each boot weighs about 16 lb. Sometimes
the main part of the boot-golosh, toe and heel, are in one brass
casting, with leather upper part, heavy