"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."