temperature of the Nautilus; the
barometer, which indicates the weight of the air and foretells the
changes of the weather; the hygrometer, which marks the dryness of the
atmosphere; the storm-glass, the contents of which, by decomposing,
announce the approach of tempests; the compass, which guides my course;
the sextant, which shows the latitude by the altitude of the sun;
chronometers, by which I calculate the longitude; and glasses for day
and night, which I use to examine the points of the horizon, when the
Nautilus rises to the surface of the waves."

"These are the usual nautical instruments," I replied, "and I know the
use of them. But these others, no doubt, answer to the particular
requirements of the Nautilus. This dial with movable needle is a
manometer, is it not?"

"It is actually a manometer. But by communication with the water,
whose external pressure it indicates, it gives our depth at the same
time."

"And these other instruments, the use of which I cannot guess?"

"Here, Professor, I ought to give you some explanations. Will you be
kind enough to listen to me?"

He was silent for a few moments, then he said:

"There is a powerful agent, obedient, rapid, easy, which conforms to
every use, and reigns supreme on board my vessel. Everything is done
by means of it. It lights, warms it, and is the soul of my mechanical
apparatus. This agent is electricity."

"Electricity?" I cried in surprise.

"Yes, sir."

"Nevertheless, Captain, you possess an extreme rapidity of movement,
which does not agree well with the power of electricity. Until now,
its dynamic force has remained under restraint, and has only been able
to produce a small amount of power."

"Professor," said Captain Nemo, "my electricity is not everybody's.
You know what sea-water is composed of. In a thousand grammes are
found 96 1/2 per cent. of water, and about 2 2/3 per cent. of chloride
of sodium; then, in a smaller quantity, chlorides of magnesium and of
potassium, bromide of magnesium, sulphate of magnesia, sulphate and
carbonate of lime. You see, then, that chloride of sodium forms a
large part of it. So it is this sodium that I extract from the
sea-water, and of which I compose my ingredients. I owe all to the
ocean; it produces electricity, and electricity gives heat, light,
motion, and, in a word, life to the Nautilus."

"But not the air you breathe?"

"Oh! I could manufacture the air necessary for my consump