"Now, if water is not absolutely incompressible, it is at least capable of very slight compression. Indeed, after the most recent calculations this reduction is only .000436 of an atmosphere for each thirty feet of depth. If we want to sink 3,000 feet, I should keep account of the reduction of bulk under a pressure equal to that of a column of water of a thousand feet. The calculation is easily verified. Now, I have supplementary reservoirs capable of holding a hundred tons. Therefore I can sink to a considerable depth. When I wish to rise to the level of the sea, I only let off the water, and empty all the reservoirs if I want the Nautilus to emerge from the tenth part of her total capacity."
I had nothing to object to these reasonings.
"I admit your calculations, Captain," I replied; "I should be wrong to dispute them since daily experience confirms them; but I foresee a real difficulty in the way."
"What, sir?"
"When you are about 1,000 feet deep, the walls of the Nautilus bear a pressure of 100 atmospheres. If, then, just now you were to empty the supplementary reservoirs, to lighten the vessel, and to go up to the surface, the pumps must overcome the pressure of 100 atmospheres, which is 1,500 lbs. per square inch. From that a power----"
"That electricity alone can give," said the Captain, hastily. "I repeat, sir, that the dynamic power of my engines is almost infinite. The pumps of the Nautilus have an enormous power, as you must have observed when their jets of water burst like a torrent upon the Abraham Lincoln. Besides, I use subsidiary reservoirs only to attain a mean depth of 750 to 1,000 fathoms, and that with a view of managing my machines. Also, when I have a mind to visit the depths of the ocean five or six mlles below the surface, I make use of slower but not less infallible means."
"What are they, Captain?"
"That involves my telling you how the Nautilus is worked."
"I am impatient to learn."
"To steer this boat to starboard or port, to turn, in a word, following a horizontal plan, I use an ordinary rudder fixed on the back of the stern-post, and with one wheel and some tackle to steer by. But I can also make the Nautilus rise and sink, and sink and rise, by a vertical movement by means of two inclined planes fastened to its sides, opposite the centre of flotation, planes that move in every direction, and that are worked by powerful levers from the interior. If the planes are kept parallel with the boat, it moves horizontally. If slanted, the Nautilus, according to this inclination, and under the influence of the screw, either sinks diagonally or rises diagonally as it suits me. And even if I wish to rise more quickly to the surface, I ship the screw, and the pressure of the water causes the Nautilus to rise vertically like a balloon filled with hydrogen."
"Bravo, Captain! But how can the steersman follow the route in the middle of the waters?"
"The steersman is placed in a glazed box, that is raised about the hull of the Nautilus, and furnished with lenses."
"Are these lenses capable of resisting such pressure?"
"Perfectly. Glass, which breaks at a blow, is, nevertheless, capable of offering considerable resistance. During some experiments of fishing by electric light in 1864 in the Northern Seas, we saw plates less than a third of an inch thick resist a pressure of sixteen atmospheres. Now, the glass that I use is not less than thirty times thicker."
"Granted. But, after all, in order to see, the light must exceed the darkness, and in the midst of the darkness in the water, how can you see?"
"Behind the steersman's cage is placed a powerful electric reflector, the rays from which light up the sea for half a mile in front."
"Ah! bravo, bravo, Captain! Now I can account for this phosphorescence in the supposed narwhal that puzzled us so. I now ask you if the boarding of the Nautilus and of the Scotia, that has made such a noise, has been the result of a chance rencontre?"
"Quite accidental, sir. I was sailing only one fathom below the surface of the water when the shock came. It had no bad result."
"None, sir. But now, about your rencontre with the Abraham Lincoln?"
"Professor, I am sorry for one of the best vessels in the American navy; but they attacked me, and I was bound to defend myself. I contented myself, however, with putting the frigate hors de combat; she will not have any difficulty in getting repaired at the next port."
"Ah, Commander! your Nautilus is certainly a marvellous boat."
