We closed up the Dolphin. The turret slid down after us. For all my hundred sub-sea trips in the Pacific, my heart was beating fast. Polly touched my hand, as we moved forward along the passage. Her fingers were cold; but in the dim light I caught her sturdy glance, and saw that her lips were smiling. “Starting, Jeff--at last.” “Yes.” I pressed her hand. We gathered, all three of us, in the bow instrument room. Dr. Plantet fingered the control levers. The Franklin lights sputtered and glowed with their steady white beams; through the circular windows, the light sprayed ahead of us in the green ocean just below the surface. The jacket-pumps were throbbing. The windows dimmed a trifle with the passing sheet of water; but when it flashed faster, they brightened. The Parodyne atomic engine was operating; the water tanks were filling under pressure; the lateral planes, like fins, were extended from the hull outside. We had settled, barely to tip the surface. I flung the water-ballast to the bow; in the silence with only the burring of the Parodyne and the humming of the pumps, the water came forward with a swish. The bow dipped. I held the rudder-levers; and released the atomic streams. We slid smoothly forward and downward. Little Dolphin, sliding, forcing its way into the depths, with green phosphorescent sprays of fire from its sides. * * * * * It is not my present purpose to describe in detail this voyage. Under other, less vital circumstances, it would have had a scientific interest beyond any enterprise of the sea which for centuries had been undertaken. But we were too engrossed in what we sought--too absorbed in the possibility that at any moment we, like those others, might be attacked. In what strange, unnatural fashion we could not guess. It kept us tense--an aspect of the voyage which we had hardly discussed, but of which we were very keenly aware, every moment. We had only one weapon--the torpedo tube. Six small torpedoes, each loaded with some three hundred pounds of trinitrotoluene as its explosive charge. There were also a dozen of the more modern cylinder bombs of miscellaneous variety, to be dispatched through the same tube. A mere gesture of warfare! I could not feel that against this enemy it would be more than a gesture. We slid down from the surface. Ah, that first plunge! At the beginning it was no more than running level, save that I could feel the Parodyne laboring a trifle and our forward thrust slackening. There was nothing to see but the dim green water rushing at our lights. Then I saw a fish of an unfamiliar type; it hung stupidly in the light and then moved away. We very nearly struck it. Five hundred fathoms. A thousand. The red column in the pressure indicator was rising steadily. The ship was laboring, struggling. The Parodyne at its higher intensities, developed unexpected strength; the pressure pumps were humming with a shrill electrical whine. Fifteen hundred.