Jules Verne: Twenty Thousand Leagues Under the Seas

FIRST PART CHAPTER 15: An Invitation in Writing (continued)

"Correct, but under such conditions the man has no freedom. He's attached to a pump that sends him air through an india-rubber hose; it's an actual chain that fetters him to the shore, and if we were to be bound in this way to the Nautilus, we couldn't go far either."

"Then how do you break free?" I asked.

"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?"