“We use the Rouquayrol-Denayrouze device, invented by two of your fellow countrymen but refined by me for my own special uses, thereby enabling you to risk these new physiological conditions without suffering any organic disorders. It consists of a tank built from heavy sheet iron in which I store air under a pressure of fifty atmospheres. This tank is fastened to the back by means of straps, like a soldier’s knapsack. Its top part forms a box where the air is regulated by a bellows mechanism and can be released only at its proper tension. In the Rouquayrol device that has been in general use, two india-rubber hoses leave this box and feed to a kind of tent that imprisons the operator’s nose and mouth; one hose is for the entrance of air to be inhaled, the other for the exit of air to be exhaled, and the tongue closes off the former or the latter depending on the breather’s needs. But in my case, since I face considerable pressures at the bottom of the sea, I needed to enclose my head in a copper sphere, like those found on standard diving suits, and the two hoses for inhalation and exhalation now feed to that sphere.” “That’s perfect, Captain Nemo, but the air you carry must be quickly depleted; and once it contains no more than 15% oxygen, it becomes unfit for breathing.” “Surely, but as I told you, Professor Aronnax, the Nautilus’s pumps enable me to store air under considerable pressure, and given this circumstance, the tank on my diving equipment can supply breathable air for nine or ten hours.” “I’ve no more objections to raise,” I replied. “I’ll only ask you, captain: how can you light your way at the bottom of the ocean?” “With the Ruhmkorff device, Professor Aronnax. If the first is carried on the back, the second is fastened to the belt. It consists of a Bunsen battery that I activate not with potassium dichromate but with sodium. An induction coil gathers the electricity generated and directs it to a specially designed lantern. In this lantern one finds a glass spiral that contains only a residue of carbon dioxide gas. When the device is operating, this gas becomes luminous and gives off a continuous whitish light. Thus provided for, I breathe and I see.” “Captain Nemo, to my every objection you give such crushing answers, I’m afraid to entertain a single doubt. However, though I have no choice but to accept both the Rouquayrol and Ruhmkorff devices, I’d like to register some reservations about the rifle with which you’ll equip me.” “But it isn’t a rifle that uses gunpowder,” the captain replied. “Then it’s an air gun?” “Surely. How can I make gunpowder on my ship when I have no saltpeter, sulfur, or charcoal?” “Even so,” I replied, “to fire underwater in a medium that’s 855 times denser than air, you’d have to overcome considerable resistance.”