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

MODELS ILLUSTRATING THE WORKING OF THE DIVING DRESS UNDER DIFFERENT CONDITIONS, AND THE EFFECT ON THE DIVER. (See page 20.) No. 9. (Pump not Working.) Shows how the body would be squeezed dangerously if the diver went down with the pump not working, or dropped by accident quicker than the pump could keep up with the pressure of the water. The rubber bag- in the glass helmet represents the head, the middle bag in the glass cylinder represents the lungs, the lowermost bag below the glass cylinder represents the body. The helmet is fixed on the rubber cork, which closes the top of the glass cylinder. Ihe helmet has an inlet tube, connected with a syringe bulb (the pump), and an outlet valve. The bag, which represents the lung, is tied on to a tube, which passes through the rubber cork and opens in the helmet. The cylinder is closed below by a rubber cork, and is three parts filled with water, and the lowermost bag, which is tied on to a tube passing through the cork, also contains water. On sinking- the model in water—the pump not working—the upper bag dis- tends, the middle and lower bags shrink. Similarly, in a diver the blood would be driven into the head, the mouth and nose would bleed, and the breathing would become im- possible owing- to the pressure of the water on the body, the head and lungs being exposed only to the pressure of the air in the helmet. No. 10. (Pump Working.) i he head bag is shrunk, the lung bag and the body bag expanded, and a con- tinuous stream of air is escaping from the helmet. The air pressure in the helmet is made slightly greater than the water pressure outside, and the conditions are then the same as when the model is suspended in air. So with the diver, all parts of his body are pressed upon equally, and as the air pressure in his helmet is equal to the water pressure outside, no congestion of blood takes place, and he can breathe comfortably. No. ii. Ihe model diver shown in photograph No. 3 has a small hole pierced in the back of the helmet. An india-rubber syringe bulb is connected with a flask full of air, and this flask in turn is connected by a T-piece to a pipe in the diver’s helmet and to a manometer containing coloured water. The model shows that the deeper the diver goes the greater must be the pressure to force air through his helmet. The height of the column of fluid separating the level of the liquid in the right and left-hand sides of the manometer keeps just greater than the level of the hole in the diver’s helmet.