Just how far back the art of sub-marine diving dates, is a matter of
conjecture, but until the invention of the present armor and helmet in
1839, work and exploration under water was, at best, imperfect, and
could only be pursued in a very limited degree. The armor of to-day
consists of a rubber and canvas suit, socks, trousers and shirt in one,
a copper breastplate or collar, a copper helmet, iron-soled shoes, and
a belt of leaden weights to sink the diver.
The helmet is made of tinned copper with three circular glasses, one
in front and one on either side, with guards in front to protect
them. The front eye-piece is made to unscrew and enable the diver
to receive or give instructions without removing the helmet. One or
more outlet valves are placed at the back or side of the helmet to
allow the vitiated air to escape. These valves only open outwards
by working against a spiral spring, so that no water can enter. The
inlet valve is at the back of the helmet, and the air on entry is
directed by three channels running along the top of the helmet to
points above the eye-pieces, enabling the diver to always inhale fresh
air, whilst condensation on the glasses is avoided. The helmet is
secured to the breastplate below by a segmental screw-bayonet joint,
securing attachment by one-eighth of a turn. The junction between
the waterproof dress and the breastplate is made watertight by means
of studs, brass plates, and wing-nuts. A life or signal line enables
the diver to communicate with those above. The air-pipe is made of
vulcanized india-rubber with galvanized iron wire imbedded.
The cost of a complete diving outfit ranges from $750 to $1,000. The
weight of the armor and attachments worn by the diver is 246 pounds,
divided as follows:--
Helmet and breastplate, 51 pounds; belt of lead weights, 122 pounds;
rubber dress or suit, 19 pounds; iron soled shoes, 27 pounds each.
The greatest depth reached by any diver was 204 feet, at which depth
there was a pressure of 88½ pounds per square inch on his body. The
area exposed of the average diver in armor is 720 inches, which would
have made the diver at that depth sustain a pressure of 66,960 pounds
or over 33 tons.