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

Helmet Washers.-—If, as a result of wear, the helmet, when screwed hard on to the corselet, will go so far round to the right that the catch at the back is past its recess, and the front glass is not directly in front of the diver’s face, one or more paper washers should be cut out and inserted under the large leather washer at the neck of the corselet, i.e., if new leather washers are not available. To replace worn cup Leather on Piston.—Remove the piston, file off the burr at the end of the rod, unscrew the nut securing the piston and remove the old leather cup; having soaked a spare cup leather in oil, place it on the rod and secure the nut as before. The glands must be tightened up or repacked if there is much leakage round the piston-rod. Whenever a pump has been taken to pieces it should be tested, after reassembling, up to the full pressure marked on the gauge. Measuring the Delivery of the Air Pump.—The efficiency of the pump is tested by measuring its output when working against a pressure. To do this a steel reservoir or other strong vessel whose capacity is accurately known (the capacity may be measured by filling with water and weighing) is connected by means of an adaptor with the diving pump. A pressure gauge should, if possible, be connected to the reser- voir as a check on the pump gauge. When all is ready, commence turning at a steady rate of, say, 25 revolutions per minute, and note the number of revolutions required to raise the pressure to 15, 30, 45, 60 and 751bs. per square inch respectively; the theo- retical capacity being ascertained, the leakage can then be calculated. Testing the Pressure Gauges.—To ensure bringing a diver up safely from deep water, it is necessary that the gauges on the pump should indicate correctly— particularly at depths less than 60ft. In the absence of other means, they may be tested by sinking the end of the air pipe (on a lead line, for instance) to 10ft. and to 50ft., and observing whether they indicate these depths correctly. When the orifice of the air pipe is at the required depth, the pump should be worked till air escapes ; it is then stopped and the front of the gauge tapped lightly while the reading is taken. DRESSING THE DIVER AND SENDING HIM DOWN. Duties of those in Charge of Diving Operations. A strong broad-beamed boat should always be used for diving operations. Having got everything necessary into the boat, arrange the position of the ladder and pump. The pump must be out of the way of the diver and the men attending him ; it must be placed so that the attendants can have a clear view of the pressure gauges, and so that the men working it may have as much room as possible. Secure lashings are to be passed to ensure the pump being quite rigid in the boat. While the diver is dressing, 'œ