This noise in the valves is a sign that the submerging mechanism is at work.
The music continues, but in a long downward scale, and during these long drawn out, ever-deepening sounds, one has a bodily feeling as of the rushing in and flooding of mighty masses of water. One seems oneself to grow heavier and to sink with the boat.
Through the window of the conning-tower and by the aid of the periscope it is now possible to observe how the front part of the boat is sinking; the railings are cutting their foaming way through the waves, while the water round the conning-tower rises higher and higher, till everything outside is wrapped in the wonderful twilight of the deep.
Only our faithful lamps are shining. Now it has indeed become silent. The only sound that reaches the ears is the soft swaying rhythm of the electric engines.
Then comes the command:
"Go down to eleven fathoms!"
"Both engines half-steam ahead!"
By the gauge I can follow the depths we are making. Through the flooding we have added several tons of dead weight to the boat. We have made the closed up ship's body heavier than the mass of water displaced—and our giant fish sinks—almost falls—into her element down below.
At the same time we are moving with the electric engines, and the forward thrust of the propeller brings pressure and reaction upon the diving rudder, and transforms the sinking into a downward gliding movement.
When the desired depth is reached, which I can tell at once from the depth gauge, further sinking is prevented by the simple means of making the boat lighter again through pumping out the superfluous water from the submersion tanks.