pass into view, while a scale in the field of vision showed in what direction the periscope was turned.
“You see,” explained our guide, “we can run along twenty feet under water with only this tube sticking above the surface. It is such a small object that no one would notice it, and yet we can see perfectly all around us, and manœuver the boat in absolute safety.”
“But don't you ever go deeper than that? I thought you went down to the bottom of the sea.”
Longitudinal Section of a torpedo on a submarine boat.
“Where the sea is no more than two hundred feet deep, we can go to the bottom; but below that the pressure grows too heavy, and eventually it would be enough to crush the boat. After all, it is n't necessary to go very deep. If we run along at a depth of sixty feet, we are sure to clear all shipping, and no one could possibly find us.”
“Can you see under water?” I asked.
“No, not more than one hundred feet or so, and then very dimly, as if in a fog. When completely under water, we have to go by dead reckoning.”
Just then the captain came aboard. At the word of command the gang-plank was raised, the hawsers were cast off, and the crew took up their positions. The engines were started, and we were off, Those engines certainly were interesting. Powerful little fellows they were, too. Between them they developed over 500-horse-power. Each engine drove its own propeller, We squeezed down the narrow passageway between them, and saw that the propeller-shafts passed through the electric motors which drive the vessel when completely under water. The armatures of the motors were mounted directly on the shafts, and so they revolved with the shafts when driven by the engines. But the circuit of the field windings was open, and no electric current was generated, so the armatures made no load on the shafts, but merely took the place of fly-wheels.
We climbed up through the hatchway to see what was going on without. As I stuck my head out of the manhole, I was astonished at the speed we seemed to be making. With my eye so close to the water, the waves seemed to be racing by with the speed of an express-train.
We had no sooner taken a good look at our surroundings than orders were given to strip the upper works. The masts at each end of the boat were on hinges, and they were swung down upon the deck. The bridge was dismantled and passed in sections down the hatchway. The hand rope and the stanchions that supported it were taken down, and presently the smooth, rounded back of the submarine was bare of every obstruction except the conning-tower and the periscopes. We all crept inside, and the hatch was closed behind us. There were eighteen men besides ourselves within the hold of that tiny vessel. The gasolene engines had already been stopped, and we were now running with our electric motors, It was astonishing how quiet everything was. There was only the slight hum of the motors and the sound of the spray at our bow, The quartermaster continued navigating the craft from within the conning-tower.
“Fill the main ballast tank!” called the captain. “Fill the forward trimming tank!" A moment later, “Fill the after trimming tank!”
We could hear the water rushing into the big U-shaped tank that lay under our feet and extended part way up the walls at either side of us. The pointer of a large depth-gage told us just how fast we were sinking. When we were awash, the motors, which had been stopped while the tanks were being filled, were started again.
“Why don’t you run the boat with gasolene engines?” I asked the chief gunner’s mate.
“Why, man alive, we have n’t air enough. Those little beasts would gobble up all our air in five minutes, and then they would stop working. As a matter of fact, the engines would suffocate long before the crew. We tried that once, Everything was closed air-tight and the engines were started. They had n’t run five minutes before they stopped. But we could still breathe easily, although the sensation was not very pleasant,”
“Where do you get fresh air from, anyway?” asked Will.
“Fresh air? We don’t get any.”
“But you have compressed air to live on while you ‘re under water—have n’t you?”
