I opened the trap and looked down, but quickly shut it again when I felt the air rushing out of the ship into the rarefied atmosphere in a torrent. Gibbons literally yelled a protest from his instrument board. "I forgot," I mumbled. "Silly of me. Of course, we'll have to drop out of compartment." The compartment, to which I referred, was similar to those in some of the 20th Century submarines. We all entered it. There was barely room for us to stand, shoulder to shoulder. With some struggles, we got into our special air helmets and adjusted the pressure. At our signal, Gibbons exhausted the air in the compartment, pumping it into the body of the ship, and as the little signal light flashed, Wilma threw open the hatch. Setting the ultron-wire reel, I climbed through, and began to slide down gently. We all had our belts on, of course, adjusted to a weight balance of but a few ounces. And the five-mile reel of ultron wire that was to be our guide, was of gossamer fineness, though, anyway, I believe it would have lifted the full weight of the five of us, so strong and tough was this invisible metal. As an extra precaution, since the wire was of the purest metal, and therefore totally invisible, even in daylight, we all had our belts hooked on small rings that slid down the wire. I went down with the end of the wire. Wilma followed a few feet above me, then Barker, Gaunt and Blash. Gibbons, of course, stayed behind to hold the ship in position and control the paying out of the line. We all had our ultrophones in place inside our air helmets, and so could converse with one another and with Gibbons. But at Wilma's suggestion, although we would have liked to let the Big Boss listen in, we kept them adjusted to short-range work, for fear that those who had been clearing with the Hans, and against whom we were on a raid for evidence, might also pick up our conversation. We had no fear that the Hans would hear us. In fact, we had the added advantage that, even after we landed, we could converse freely without danger of their hearing our voices through our air helmets. For a while I could see nothing below but utter darkness. Then I realized, from the feel of the air as much as from anything, that we were sinking through a cloud layer. We passed through two more cloud layers before anything was visible to us. Then there came under my gaze, about two miles below, one of the most beautiful sights I have ever seen; the soft, yet brilliant, radiance of the great Han city of Nu-yok. Every foot of its structural members seemed to glow with a wonderful incandescence, tower piled up on tower, and all built on the vast base-mass of the city, which, so I had been told, sheered upward from the surface of the rivers to a height of 728 levels.