‘Way down in Tennessee----’ continued the worker, ignoring the insult, in a masterly manner. Through the door in the engine-room bulkhead came the Chief E.R.A. to hurl an insult at a tardy message-bearer, but the hoot of the telegraph sent him diving back to his lair almost immediately. ‘Stop ’er,’ cried the L.T.O., working the switches to the accompaniment of a hiss and crackle of blue sparks. ‘Engines!’ came Raymond’s voice from above. ‘Three hundred revs.!’ ‘Engines!’ shouted Furness, the L.T.O., into the engine-room. ‘Three ’undred!’ ‘The ‘Chief’ waved a reply, and with a snip of switches the motors started again. Then the engine clutches came home and the Diesels began to heave with a fizz bump, fizz bump, fizz, fizz, fizz, as the needles of the ammeters came back from discharging, past zero and on to charging. Once more Hoskins waved a grimy hand and the motor workers broke their switches. She was away on her engines at ten knots now, her exhaust, which had started in oily puffs, rapidly thinning astern to a white semi-transparent vapour. Into the battery-room at this juncture came the ‘Sub’ of the boat, an ingenuous youth of nineteen, bearing upon his youthful shoulders as second in command all the anxieties and troubles of the world. ‘All right, Furness?’ he asked. ‘Yessir, she went off very well.’ ‘Good,’ replied Seagrave, looking at the volt-metre on the low-power switchboard. ‘Keep the lighting down to a hundred and ten.’ He wandered off under the mess tables, clipped up to the steel ceiling of the compartment to examine the gyro master-compass, a large mushroom-shaped object of steel and electricity, whose rotor buzzed round at the rate of over eight thousand revolutions a minute. On his left were the electric cooking range, lockers and battery ventilators, and overhead were the great vents which let the air out of the main ballast tanks when the boat dived. Presently, satisfied with the ‘Sperry’ compass, he stepped forward through the watertight door into the control room, a regular holy of holies, on whose shrine were offered many tins of ‘Brasso’ daily and much elbow grease and bad language by heated and voluble ‘matlows.’[5] Here were the levers which opened the great Kingston valves in the bottom of the boat and flooded the tanks for diving. Here was the adjusting pump, by means of which water could be pumped from any one tank to another and into or from the sea. Aft was the periscope, a long steel tube sticking up through the roof, fitted with an eye-piece and graduated rings at its lower end. On the port side were the hydroplane and diving rudder wheels, and the depth and pressure gauges. Forward was the air manifold, by means of which, on opening the Kingston valves, air could be blown into the tanks at a pressure of over 75 lbs. to the square inch, and so force the water out of them when the captain wished the boat to rise.