A few moments later he sent a signal to Murgatroyd in the engine-room. The propellers began to revolve slowly, beating the dense air and driving the _Astronef_ at a speed of about twenty miles an hour through the depths of this strangely peopled ocean. They approached nearer and nearer to the surface, and as they did so the uncanny creatures about them grew more and more numerous. They were certainly the most extraordinary living things that human eyes had ever looked upon. Zaidie's comparison to the whale and the jelly-fish was by no means incorrect; only when they got near enough to them they found, to their astonishment, that they were double-headed--that is to say, they had a head with a mouth, nostrils, ear-holes, and eyes at each end of their bodies. The larger of the creatures appeared to have a certain amount of respect for each other. Now and then they witnessed a battle-royal between two of the monsters who were pursuing the same prey. Their method of attack was as follows: The assailant would rise above his opponent or prey, and then, dropping on to its back, envelop it and begin tearing at its sides and under parts with huge beak-like jaws, somewhat resembling those of the largest kind of the earthly octopus, only infinitely more formidable. The substance composing their bodies appeared to be not unlike that of a terrestrial jelly-fish, but much denser. It seemed from their motions to have the tenacity of soft indiarubber save at the headed ends, where it was much harder. The necks were protected for about fifty feet by huge scales of a dull, greenish hue. When one of them had overpowered an enemy or a victim the two sank down into the vegetation, and the victor began to eat the vanquished. Their means of locomotion consisted of huge fins, or rather half-fins, half-wings, of which they had three laterally arranged behind each head, and four much longer and narrower, above and below, which seemed to be used mainly for steering purposes. They moved with equal ease in either direction, and they appeared to rise or fall by inflating or deflating the middle portions of their bodies, somewhat as fish do with their swimming bladders. The light in the lower regions of this strange ocean was dimmer than earthly twilight, although the _Astronef_ was steadily making her way beneath the arch of the rings towards the sunlit hemisphere. "I wonder what the effect of the searchlight would be on these fellows!" said Redgrave. "Those huge eyes of theirs are evidently only suited to dim light. Let's try and dazzle some of them."