Reproduction of a chart published by the German Hydrographic Office, giving a list of wrecks which have occurred in the locality pictured during a period of only fifteen years. This great loss of shipping was one of the principal causes leading up to the construction of the Kiel canal.
In many waters the divers would be engaged in plain view of their tenders in the operating compartment, who would handle the down-pull lines and transmit signals by bell or telephone to the control station on the boat above. Work is thus carried on continuously by relays of divers who are thoroughly conversant with the progress of the undertaking and the circumstances affecting performance. Through the medium of the equalizing room the divers, who leave their helmets, shoes, and weights in the operating chamber, are able to undergo slowly and comfortably either decompression or compression after or before each shift. They can remain in the equalizing room as long as necessary to effect this in the way most conducive to their physical well-being. This compartment is well lighted, is fitted with seats, and provides every reasonable convenience for the diver during this intermediate stage.
Statistics have been published to show that practically the entire commerce of the world sinks in every twenty-five years. In the present war the rate of sinking has been, of course, enormously accelerated, and millions of tons of ships have been sunk, with billions of dollars' worth of cargo. Many of these vessels were sunk in the North Sea or the English Channel, where the water is comparatively shallow, and where many of the cargoes can undoubtedly be recovered with the proper apparatus. The loss of ships in peace times is such a common occurrence that little attention is paid to them except when their loss is accompanied by great loss of life, as was the case with the Titanic, the Monroe, the Empress of Ireland, or the Lusitania. There are therefore great opportunities for devices of this nature to operate profitably.
Another use to which the submarine may be put is the recovery of shellfish from the sea bottom. For such work as this adaptations of the submarine vessel are well fitted.
A submarine vessel of the "Lake" bottom-working type has been designed and is now being built for the location of and the recovery of shellfish on a large scale. Shellfish abound on both the Atlantic and Pacific coasts in great quantities. They are about the most delicious and nutritious food known to man. The most common shellfish are the oyster, the round or hard-shell clam, the long-neck or soft-shell clam, the scallop, and, on the Pacific coast, the abalone, which is valuable both for its mother-of-pearl shell and its meat, which is a great delicacy, the most of which is sent to Japan, either dried or canned.
My own sea-bottom investigations, combined with the sea-bottom investigations of the United States Fish Commission, have led me to the conclusion that edible shellfish abound along our coast in such great quantities that they can become an important rival to our meat-growing and packing industries, provided the proper apparatus is used for their recovery. I have, when "wheeling" along the bottom, found beds of the round or hard-shell clam in such great quantities that there must have been thousands of bushels to the acre. This was in waters too deep to be recovered by the usual clammers' apparatus. It is impossible to dredge for the soft-shell clam, as the shell is too delicate, and to pull them out of their bed would crush them. The abalone attach themselves to rocks, and it requires considerable force to break their hold, so there is no known means to recover them with surface ships.
The oyster industry is the only one that has thus far been developed by planting and cultivating methods, so that it is now a great industry, employing thousands of steam, internal-combustion, and sail boats in their cultivation and collection for the market. The method employed by the largest growers is by the use of power boats which drag dredges. These are rakes with a meshed bag dragging on the bottom back of the tooth bar of the dredge to collect the oysters after they are raked or torn up from their beds. This is not a scientific method, for the reason that many of the oysters are killed by the heavy dredge being dragged over them. It is largely a hit-or-miss or grab-in-the-dark method, as it is impossible to clean up the ground in this manner. Some oyster grounds will produce from three to four thousand bushels of oysters to the acre. When dredging is started it is only necessary to drag the dredge a few feet before it is filled; then, as the oysters become thinner, the drag becomes longer. They drag in all directions across the grounds, but, as they cannot see the bottom, there are places they never hit, because the wind and currents prevent a systematic covering of the ground.
