When all the others of us were below, the captain came squeezing down from the conning-tower hatch and took his position at the periscope.
To the captain's left stood a man whose job it was to hold the sub to the depth of water desired. This was the diving-rudder man, a most expert one, we were told, who had been known to hold a submerged sub at full speed to within six inches of one depth for two miles at a stretch. A thin brass scale and a curved tube of colored water with an air bubble in it helped out the diving-rudder man's calculations. The least deviation of the sub's course from the horizontal and these two instruments, lit up by electric lamps, showed it at once. There was a big dial, with a long green hand, which also marked the depth of the sub; but that was an insensitive and rather slow-acting gauge—all right for the crew to look at from half the length of the sub, but not fine or quick enough for the diving-rudder man.
He was the busy man while we were under water. The others could now and again grab a moment of relaxation from their tenseness, but while the sub was moving the diving-rudder man never took his eyes off the little brass scale with the electric light playing on it. Stop and consider that our sub had only to get a downward inclination of ever so little while running hooked-up under water, and in no time she would be below her lowest safety depth of 200 feet, where the pressure is 7 tons to every square foot of her hull. And should she collapse there would be no preliminary small leak by way of warning. She would go as an egg-shell goes when you crush it in your palm. Plack!—like that—and it would be all over. Above this same middle compartment, the smallest and most crowded of all, up through the grilled spaces of a steel grating, we could see the wide feet and boot-legs of the man who held the ship to her compass course; and for a wheel, we knew, he was holding a little metal lever about as long and thick as his middle finger, with a little black ball about as big as the ball of his thumb on the end of it.
To the right of the foot of the conning-tower ladder stood the ballast-tank man; and when the captain from the foot of his periscope gave the word—after first looking forward, aft, and to each side of him to see that all hands were at their proper stations—it was the ballast-tank man who went violently at once into action. He grabbed a big valve and gave it a twist; grabbed another and gave it a twist; and another, and one more; and, standing near by, we could hear—or thought we could—the in-rush of great waters.
In the engine-room of a submarine.
The Diesel engines, driven by crude petroleum, propel the ship on the surface. Electric motors supply the power when running submerged.[ToList]
A man got to wondering then what would happen if this chap got his valves mixed. But a look around showed every lever and every valve, everything marked with its own name and number. Nothing was left unmarked—in deep-cut black lettering on brass plates generally, but here and there colored-light signs, too. After another look at the multiplicity of them, almost any man would agree that it is a good scheme.
But to get back: the tank man has done his part and our sub is sinking. There is no unusual feeling to inform a man she is sinking. Only for the starting of the engines, the diving-rudder man getting busy, and the wide-faced gauge's long green finger beginning to walk around, a man who didn't know could easily believe that the sub was still tied up alongside her supply-ship. But the long green finger is walking, and marking 5 feet, 10 feet, 11, 12, as it walks. At 16 feet the finger oscillates and stops, and to that depth our diving-rudder man holds her while she speeds on for a mile or so.
That first little dash is by way of warming her up. The officer for whose government this submarine was built is aboard. He now asks for a torpedo demonstration. So two 1,500-pound dummy torpedoes are got ready, the breeches to two of the four forward tubes opened, the torpedoes slipped in, the breeches closed. The bow caps are then opened.