Submarine Appliances And Their Uses
Deep Sea Diving, &c., &c.

T riewald’s Bell. Fig, 91. In 1728, Martin Triewald, a Swedish military officer, contrived a diving bell of a lighter and less expensive character than Halley’s. This bell, as shown in Fig. 91, was made of copper, tinned on the inside, and was sunk by the lead weights (W W) suspended round the mouth. The iron plate (E) on which the diver stood was suspended by chains (F F) at such a distance from the bottom of the bell that, when he stood up- right, his head reached just above the water in the bell, where he had the advantage of the coolest air. A spiral tube was fitted, by which a diver inside the bell could inhale the cooler and fresher air at the bottom through a mouthpiece (M). Air was sup- plied to this bell in the same way as Halley’s. Charles Spalding introduced an improvement on Halley’s bell, the ob- ject being to make it more portable, safer to handle, and to allow the clivers to have control over it. In shape the bell was like into a separate chamber by the watertight partition (E F). The bell was weighted with slabs of lead (D I)) hung from hooks (S S) to keep it perpendicular in the water, but these weights were not sufficient to sink the bell without the addition of the balance weight (W), which was hung from the centre ot the bell by pulley blocks, and allowed to reach down some distance below the bottom of the bell. By lowering this weight to the bottom, the bell, being thus relieved of a weight of about 3 cwt., immediately rises, and any strain on the suspension rope, or danger of being capsized by any obstacle in its descent, are thus avoided. By means of cocks (G L), water or air may be admitted to the upper chamber (P), so that the bell may be made to sink or rise in the water at pleasure. As in the case of Halley’s bell, fresh air was supplied by lowering barrels. (See Fig. 92.) Halley’s, but the upper part (P) was formed Fig. 92.