contained in 100 litres (22 gallons) of atmospheric air, and this air, then almost equal to carbonic acid gas, becomes insupportable.
It was, therefore, necessary to renovate the air of our prison, and, without doubt, also the atmosphere of our submarine boat.
Here was a puzzling question. How did the commander of the floating dwelling get on? Did he obtain air by chemical means, by disengaging the oxygen contained in chlorate of potash, and by absorbing the carbonic acid by the caustic potash? In this case he must keep up a communication with the earth to obtain a supply of these materials. Did he only take the precaution to store the air under great pressure in reservoirs, and free it again according to the requirements of the ship’s company? Perhaps so. Or, what was a much easier method, more economical, and therefore more probable, was that he came up to the surface of the water to breathe, like a cetacean, and for twenty-four hours renew his supply of oxygen. However it might be, and by whatever means, it appeared to me prudent to employ it without delay.
In fact I was already obliged to breathe more quickly to extract what little oxygen the cell contained, when I was suddenly refreshed by a current of pure air, perfumed with the odour of the sea. It was the true sea-breeze vivified and charged with iodine. I opened my mouth wide. I was sensible of a rocking motion, a rolling of some extent, but perfectly determinable. The monster had evidently come up to the surface to breathe, after the fashion of the whale. The mode of ventilating the ship was now perfectly apparent.
