Deep-Sea Diving (continued)
Before the diver is ready to descend into the water a number of weights are adjusted across his chest and back in such a manner that they cannot possibly become detached. These are necessary to enable him to descend with facility to the depths of the ocean and walk about the floor of the ocean, and also to permit him to maintain his equilibrium while he is below. Every diver wears a heavy waist-belt, in which he carries a strong knife in a metal case for emergency purposes, and sometimes any other small tools that may be essential for the particular task he has in hand.
The greatest depth to which any diver has been known to descend is one hundred and eighty two feet. Those engaged in the Mediterranean sponge fisheries frequently descend to a depth of one hundred and fifty feet, while the pearl divers of Australia go down a hundred and twenty feet.
For special kinds of work, such as laying the foundations for bridges, breakwaters, etc., the diving bell is employed. This consists of a cast-iron box without a bottom, and weighs about five tons. The top of the diving bell is supplied with stout glass windows, so as to admit the light, and also with a connection into which the air supply pipe, which is connected to a force pump, is screwed. Inside, the bell is fitted with two seats and a suspending chain, to which immense stones or concrete blocks can be attached. The bell is suspended from a barge, or platform, by chains attached to the top, and is used in from thirty to thirty-five feet of water.
In addition to its scientific and photographic value, the Williamson deep-sea tube has many other practical applications. One has only to read the list of treasure ships which foundered in fairly shallow water to realise what a fascinating field of profit is here. Millions upon millions of pounds in coins, gold and silver bars, ivory and precious stones, and valuable jewels, have gone to the bottom of the ocean by the foundering of treasure ships. Most of this treasure has been given up as lost forever to the world, but the Williamson apparatus is a hint that much of it may one day be recovered.
During their exploration of the sea bottom, the Williamson brothers located an old wreck, which it was afterwards ascertained was that of one of the vessels engaged in blockade running during the American Civil War. Mr. George Williamson arranged to descend for a closer examination and inspection of the submerged wooden vessel. This was by no means an easy task, for while he was exploring the ship, on which he had great difficulty to maintain his equilibrium, he was working under the pressure of two atmospheres. This means that there was a pressure of about thirty pounds on every square inch of his diving suit. After some trouble, he managed to wrench off the ship's bell, which, after examination, was found to contain a Spanish inscription, and then, with his hatchet, chopped off a piece of the wreck to keep as a souvenir of his exploit.