EXPLORING THE SEA BOTTOM IN A DIVER'S SLED
The diver's sled is still another interesting German invention. It is a sled provided with vertical and horizontal rudders, which is towed by means of a motor-boat at the surface. The diver, seated on the sled, and provided with a self-contained diving-suit, can direct the motor-boat by telephone and steer his sled up and down and wherever he chooses. And so without any physical exertion, he can explore the bottom of the sea and hunt for wrecks.
From time to time attempts have been made to construct a diver's suit that will not yield to the pressure of the sea, so that the diver will not be subjected to the weight of the water about him, but can breathe air at ordinary atmospheric pressure. Curious armor of steel has been devised, with articulated arms and legs, in which the diver is completely encased. With the ordinary rubber suit, the diver usually has his hands bare, because he is almost as dependent upon the sense of touch as a blind man. But where the pressure mounts up to such a high degree that a metal suit must be used, no part of the body may be exposed. If a bare hand were extended out of the protecting armor it would immediately be mashed into a pulp and forced back through the opening in the arms of the suit. The best that can be done, then, is to furnish the arms of the suit with hooks or tongs or other mechanical substitutes for hands which will enable the diver to make fast to the wreck or various parts of it.
But if a diver feels helpless in the bag of a suit now commonly worn, what would he do when encased in a steel boiler; for that is virtually what the armored suit is! A common mistake that inventors of armor units have made is to fail to consider the effects of the enormous hydraulic pressure on the joints of the suit. In order to make them perfectly tight, packings must be employed, and these are liable to be so jammed by the hydraulic pressure that it is well nigh impossible to articulate the limbs. Again, the construction of the suit should be such that when a limb is flexed it would not displace any more water than when in an extended position, and vice versa. A diver may find that he cannot bend his arm, because in doing so he would expand the cubical content of his armor by a few cubic inches, and to make room for this increment of volume it would be necessary for him to lift several hundred pounds of water. The hydraulic pressure will reduce the steel suit to its smallest possible dimensions, which may result either in doubling up the members or extending them rigidly.