Now about the air in the projectile. There, too,they were secure. Reiset and Regnaut's apparatus,intended for the production of oxygen, was supplied with chlorate of potassium for two months. They necessarily consumed a certain quantity of gas, for they were obliged to keep the producing substance at a temperature of above 400@. But there again they were all safe. The apparatus only wanted a little care.But it was not enough to renew the oxygen; they must absorb the carbonic acid produced by expiration.During the last twelve hours the atmosphere of the projectile had become charged with this deleterious gas. Nicholl discovered the state of the air by observing Diana panting painfully. The carbonic acid,by a phenomenon similar to that produced in the famous Grotto del Cane, had collected at the bottom of the projectile owing to its weight. Poor Diana, with her head low, would suffer before her masters from the presence of this gas. But Captain Nicholl hastened to remedy this state of things, by placing on the floor several receivers containing caustic potash, which he shook about for a time, and this substance, greedy of carbonic acid, soon completely absorbed it, thus purifying the air.