CHAPTER 13: Some Figures
"I'm all ears, captain."
"When I wanted to determine what increase in weight the Nautilus
needed to be given in order to submerge, I had only to take note
of the proportionate reduction in volume that salt water experiences
in deeper and deeper strata."
"That's obvious," I replied.
"Now then, if water isn't absolutely incompressible, at least
it compresses very little. In fact, according to the most
recent calculations, this reduction is only .0000436 per atmosphere,
or per every thirty feet of depth. For instance, to go 1,000
meters down, I must take into account the reduction in volume
that occurs under a pressure equivalent to that from a 1,000-meter
column of water, in other words, under a pressure of 100 atmospheres.
In this instance the reduction would be .00436. Consequently, I'd have
to increase my weight from 1,507.2 metric tons to 1,513.77. So
the added weight would only be 6.57 metric tons."
"That's all, Professor Aronnax, and the calculation is easy to check.
Now then, I have supplementary ballast tanks capable of shipping 100
metric tons of water. So I can descend to considerable depths.
When I want to rise again and lie flush with the surface, all I
have to do is expel that water; and if I desire that the Nautilus
emerge above the waves to one-tenth of its total capacity, I empty
all the ballast tanks completely."
This logic, backed up by figures, left me without a single objection.
"I accept your calculations, captain," I replied, "and I'd be ill-mannered
to dispute them, since your daily experience bears them out.
But at this juncture, I have a hunch that we're still left with
one real difficulty."
"What's that, sir?"
"When you're at a depth of 1,000 meters, the Nautilus's plating
bears a pressure of 100 atmospheres. If at this point you want
to empty the supplementary ballast tanks in order to lighten your
boat and rise to the surface, your pumps must overcome that pressure
of 100 atmospheres, which is 100 kilograms per each square centimeter.
This demands a strength--"