y
immersed it displaces 50,000 feet of water, or weighs 1,500 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 its 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 only 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 1,507 tons, will be completely immersed.
That would happen, Professor. These reservoirs are in the lower part
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 o