Scuba Diving according to Jules Verne's 20,000 Leagues Under The Sea
A limited scuba apparatus was developed by Frenchmen Benoit Rouquayrol and Auguste Denayrouse in 1865. They patented an apparatus for underwater breathing that consisted of a horizontal steel tank of compressed air on a diver's back, connected to a valve arranged to a mouthpiece. The volume of the tank is 8 litres and the pressure 30 bars (450 psi): the scuba diver is autonomous under water. With this apparatus the diver was tethered to the surface by a hose that pumped fresh air into the low-pressure tank, but he was able to disconnect the tether and dive with just the tank on his back for a few minutes.
Jules Verne was aware of this invention and incorporated it into his 1870 novel, 20,000 Leagues Under The Sea. Although the actual Rouquayrol-Denayrouse invention could only function as a true scuba (i.e. untethered) for a few minutes at a time, Verne extended this to several hours in his novel. Inside the submarine Nautilus, just prior to long underwater hike using the scuba apparatus, Captain Nemo explains how it works to Professor Aronnax, a French naturalist (and the novel's narrator).
"You know as well as I do, Professor, that man can live under water, providing he carries with him a sufficient supply of breathable air. In submarine works, the workman, clad in impervious dress, with his head in a metal helmet, receives air from above by means of forcing pumps and regulators."
"This is a diving apparatus," said I.
"Just so, but under these conditions the man is not at liberty, he is attached to the pump which sends him air through an India-rubber tube, and if we were obliged to be thus held to the Nautilus, we could not go far."
"And the means of getting free?"
"It is to use the Rouquayrol apparatus, invented by two of your own countrymen, which I have brought to perfection for my own use, and which will allow you to risk yourself under these new physiological conditions, without any organ whatever suffering. It consists of a reservoir of thick iron plates, in which I store the air under a pressure of fifty atmospheres. This reservoir is fixed on the back by means of braces, like a soldier?s knapsack. Its upper part forms a box in which the air is kept by means of bellows, and therefore cannot escape unless at its normal tension. In the Rouquayrol apparatus such as we use, two India-rubber pipes leave this box and join a sort of tent which holds the nose and mouth; one is to introduce fresh air, the other to let out the foul, and the tongue closes one or the other according to the wants of the respirator. But I, in encountering great pressures at the bottom of the sea, was obliged to shut my head, like that of a diver, in a ball of copper; and it is to this ball of copper that the two pipes, the inspirator and the expirator, open."
"Perfectly, Captain Nemo; but the air that you carry with you must soon be used; when it only contains fifteen per cent of oxygen, it is no longer fit to breathe."
"Right! But I told you, M. Aronnax, that the pumps of Nautilus allow me to store the air under considerable pressure and on these conditions the reservoir of the apparatus can furnish breathable air for nine or ten hours."
"I have no further objections to make," I answered.
Who would object to diving for nine or ten hours with a single tank? I certainly would like to test my physical endurance under water. Might have an ample air supply left but no more energy to kick my legs any more!