## Twenty Thousand Leagues Under the Seas – Day 35 of 165

### Chapter 13: Some Figures

A moment later we were seated on a couch in the lounge, cigars between
our lips. The Captain placed before my eyes a working drawing that gave the ground plan,
cross section, and side view of the *Nautilus*. Then he began his
description as follows:

“Here, Professor Aronnax, are the different dimensions of this boat now transporting you. It’s a very long cylinder with conical ends. It noticeably takes the shape of a cigar, a shape already adopted in London for several projects of the same kind. The length of this cylinder from end to end is exactly seventy meters, and its maximum breadth of beam is eight meters. So it isn’t quite built on the ten–to–one ratio of your high–speed steamers; but its lines are sufficiently long, and their tapering gradual enough, so that the displaced water easily slips past and poses no obstacle to the ship’s movements.

“These two dimensions allow you to obtain, via a simple calculation,
the surface area and volume of the *Nautilus*. Its surface area
totals 1,011.45 square meters, its volume 1,507.2 cubic meters—which is tantamount to saying that when it’s completely submerged,
it displaces 1,500 cubic meters of water, or weighs 1,500 metric tons.

“In drawing up plans for a ship meant to navigate underwater, I wanted it, when floating on the waves, to lie nine–tenths below the surface and to emerge only one–tenth. Consequently, under these conditions it needed to displace only nine–tenths of its volume, hence 1,356.48 cubic meters; in other words, it was to weigh only that same number of metric tons. So I was obliged not to exceed this weight while building it to the aforesaid dimensions.

“The *Nautilus* is made up of two hulls, one inside the other;
between them, joining them together, are iron T–bars that give this ship
the utmost rigidity. In fact, thanks to this cellular arrangement,
it has the resistance of a stone block, as if it were completely solid.
Its plating can’t give way; it’s self–adhering and not dependent
on the tightness of its rivets; and due to the perfect union
of its materials, the solidarity of its construction allows it
to defy the most violent seas.

“The two hulls are manufactured from boilerplate steel, whose relative density is 7.8 times that of water. The first hull has a thickness of no less than five centimeters and weighs 394.96 metric tons. My second hull, the outer cover, includes a keel fifty centimeters high by twenty–five wide, which by itself weighs 62 metric tons; this hull, the engine, the ballast, the various accessories and accommodations, plus the bulkheads and interior braces, have a combined weight of 961.52 metric tons, which when added to 394.96 metric tons, gives us the desired total of 1,356.48 metric tons. Clear?”

“Clear,” I replied.

“So,” the captain went on, “when the *Nautilus* lies on the waves
under these conditions, one–tenth of it does emerge above water.
Now then, if I provide some ballast tanks equal in capacity
to that one–tenth, hence able to hold 150.72 metric tons, and if I
fill them with water, the boat then displaces 1,507.2 metric tons—or it weighs that much—and it would be completely submerged.
That’s what comes about, professor. These ballast tanks exist
within easy access in the lower reaches of the *Nautilus*. I open
some stopcocks, the tanks fill, the boat sinks, and it’s exactly
flush with the surface of the water.”

“Fine, captain, but now we come to a genuine difficulty. You’re able to lie flush with the surface of the ocean, that I understand. But lower down, while diving beneath that surface, isn’t your submersible going to encounter a pressure, and consequently undergo an upward thrust, that must be assessed at one atmosphere per every thirty feet of water, hence at about one kilogram per each square centimeter?”

“Precisely, sir.”

“Then unless you fill up the whole *Nautilus*, I don’t see how you
can force it down into the heart of these liquid masses.”

“Professor,” Captain Nemo replied, “static objects mustn’t be confused with dynamic ones, or we’ll be open to serious error. Comparatively little effort is spent in reaching the ocean’s lower regions, because all objects have a tendency to become ‘sinkers.’ Follow my logic here.”

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