Chapter 12 — Some Figures explained simply

A moment after we were seated on a divan in the saloon smoking. The Captain showed me a sketch that gave the plan, section, and elevation of the _Nautilus_. Then he began his description in these words:— “Here, M. Aronnax, are the several dimensions of the boat you are in. It is an elongated cylinder with conical ends. It is very like a cigar in shape, a shape already adopted in London in several constructions of the same sort. The length of this cylinder, from stem to stern, is exactly 232 feet, and its maximum breadth is twenty-six feet. It is not built quite like your long-voyage steamers, but its lines are sufficiently long, and its curves prolonged enough, to allow the water to slide off easily, and oppose no obstacle to its passage. These two dimensions enable you to obtain by a simple calculation the surface and cubic contents of the _Nautilus_. Its area measures 6032 feet; and its contents about 1500 cubic yards—that is to say, when completely immersed it displaces 50,000 feet of water, or weighs 1500 tons. “When I made the plans for this submarine vessel, I meant that nine-tenths should be submerged: consequently, it ought only to displace nine-tenths of its bulk—that is to say, only to weigh that number of tons. I ought not, therefore, to have exceeded that weight, constructing it on the aforesaid dimensions. “The _Nautilus_ is composed of two hulls, one inside, the other outside, joined by T-shaped irons, which render it very strong. Indeed, owing to this cellular arrangement it resists like a block, as if it were solid. Its sides cannot yield; it coheres spontaneously, and not by the closeness of its rivets; and the homogenity of its construction, due to the perfect union of the materials, enables it to defy the roughest seas. “These two hulls are composed of steel plates, whose density is from .7 to .8 that of water. The first is not less than two inches and a half thick and weighs 394 tons. The second envelope, the keel, twenty inches high and ten thick, weighs alone sixty-two tons. The engine, the ballast, the several accessories and apparatus appendages, the partitions and bulkheads, weigh 961.62 tons. Do you follow all this?” “I do.” “Then, when the _Nautilus_ is afloat under these circumstances, one-tenth is out of the water. Now, if I have made reservoirs of a size equal to this tenth, or capable of holding 150 tons, and if I fill them with water, the boat, weighing then 1507 tons, will be completely immersed. That would happen, Professor. These reservoirs are in the lower parts of the _Nautilus_. I turn on taps and they fill, and the vessel sinks that had just been level with the surface.” “Well, Captain, but now we come to the real difficulty. I can understand your rising to the surface; but diving below the surface, does not your submarine contrivance encounter a pressure, and consequently undergo an upward thrust of one atmosphere for every thirty feet of water, just about fifteen pounds per square inch?” “Just so, sir.” “Then, unless you quite fill the _Nautilus_, I do not see how you can draw it down to those depths.” “Professor, you must not confound statics with dynamics or you will be exposed to grave errors. There is very little labour spent in attaining the lower regions of the ocean, for all bodies have a tendency to sink. When I wanted to find out the necessary increase of weight required to sink the _Nautilus_, I had only to calculate the reduction of volume that sea-water acquires according to the depth.” “That is evident.” “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 3000 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 1000 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 1500 pounds 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 1000 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 miles 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.” “Yes, Professor; and I love it as if it were part of myself. If danger threatens one of your vessels on the ocean, the first impression is the feeling of an abyss above and below. On the _Nautilus_ men’s hearts never fail them. No defects to be afraid of, for the double shell is as firm as iron; no rigging to attend to; no sails for the wind to carry away; no boilers to burst; no fire to fear, for the vessel is made of iron, not of wood; no coal to run short, for electricity is the only mechanical agent; no collision to fear, for it alone swims in deep water; no tempest to brave, for when it dives below the water, it reaches absolute tranquillity. There, sir! that is the perfection of vessels! And if it is true that the engineer has more confidence in the vessel than the builder, and the builder than the captain himself, you understand the trust I repose in my _Nautilus;_ for I am at once captain, builder, and engineer.” “But how could you construct this wonderful _Nautilus_ in secret?” “Each separate portion, M. Aronnax, was brought from different parts of the globe. The keel was forged at Creusot, the shaft of the screw at Penn & Co.’s, London, the iron plates of the hull at Laird’s of Liverpool, the screw itself at Scott’s at Glasgow. The reservoirs were made by Cail & Co. at Paris, the engine by Krupp in Prussia, its beak in Motala’s workshop in Sweden, its mathematical instruments by Hart Brothers, of New York, etc.; and each of these people had my orders under different names.” “But these parts had to be put together and arranged?” “Professor, I had set up my workshops upon a desert island in the ocean. There my workmen, that is to say, the brave men that I instructed and educated, and myself have put together our _Nautilus_. Then when the work was finished, fire destroyed all trace of our proceedings on this island, that I could have jumped over if I had liked.” “Then the cost of this vessel is great?” “M. Aronnax, an iron vessel costs £45 per ton. Now the _Nautilus_ weighed 1500. It came therefore to £67,500, and £80,000 more for fitting it up, and about £200,000 with the works of art and the collections it contains.” “One last question, Captain Nemo.” “Ask it, Professor.” “You are rich?” “Immensely rich, sir; and I could, without missing it, pay the national debt of France.” I stared at the singular person who spoke thus. Was he playing upon my credulity? The future would decide that.