“SIR,” CAPTAIN NEMO SAID, showing me the instruments hanging on the walls of his stateroom, “these are the devices needed to navigate the Nautilus. Here, as in the lounge, I always have them before my eyes, and they indicate my position and exact heading in the midst of the ocean. You’re familiar with some of them, such as the thermometer, which gives the temperature inside the Nautilus; the barometer, which measures the heaviness of the outside air and forecasts changes in the weather; the humidistat, which indicates the degree of dryness in the atmosphere; the storm glass, whose mixture decomposes to foretell the arrival of tempests; the compass, which steers my course; the sextant, which takes the sun’s altitude and tells me my latitude; chronometers, which allow me to calculate my longitude; and finally, spyglasses for both day and night, enabling me to scrutinize every point of the horizon once the Nautilus has risen to the surface of the waves.” “These are the normal navigational instruments,” I replied, “and I’m familiar with their uses. But no doubt these others answer pressing needs unique to the Nautilus. That dial I see there, with the needle moving across it—isn’t it a pressure gauge?” “It is indeed a pressure gauge. It’s placed in contact with the water, and it indicates the outside pressure on our hull, which in turn gives me the depth at which my submersible is sitting.” “And these are some new breed of sounding line?” “They’re thermometric sounding lines that report water temperatures in the different strata.” “And these other instruments, whose functions I can’t even guess?” “Here, professor, I need to give you some background information,” Captain Nemo said. “So kindly hear me out.” He fell silent for some moments, then he said: “There’s a powerful, obedient, swift, and effortless force that can be bent to any use and which reigns supreme aboard my vessel. It does everything. It lights me, it warms me, it’s the soul of my mechanical equipment. This force is electricity.” “Electricity!” I exclaimed in some surprise. “Yes, sir.” “But, captain, you have a tremendous speed of movement that doesn’t square with the strength of electricity. Until now, its dynamic potential has remained quite limited, capable of producing only small amounts of power!” “Professor,” Captain Nemo replied, “my electricity isn’t the run-of-the-mill variety, and with your permission, I’ll leave it at that.” “I won’t insist, sir, and I’ll rest content with simply being flabbergasted at your results. I would ask one question, however, which you needn’t answer if it’s indiscreet. The electric cells you use to generate this marvelous force must be depleted very quickly. Their zinc component, for example: how do you replace it, since you no longer stay in contact with the shore?”