All that day they swept over the blue waters of this great body, frequently seeing ships below and sometimes small islands. Toward night they ran into such hard headwinds that Bob went up higher. He climbed steadily until the Sky-Bird had attained an altitude of nine thousand feet. Here, as expected, they found the winds much less forceful, but the sea was blotted out entirely by the clouds through which they had passed in the process of rising and which now lay between. Indeed, these clouds resembled a billowy ocean of white foam in themselves, or a landscape covered with hills and valleys of snow. The rounded cloud contours could easily be likened to the domes of snow-covered mountains. It was really difficult to conceive that that amorphous expanse was not actually solid. Here and there flocculent towers and summits heaved up, piled like mighty snow dumps, toppling and crushing into one another, as the breezes stirred them. Then there were tiny wisps of cloud, more delicate and frail than feathers or the down of a dandelion-blow. Chasms hundreds of feet deep, sheer columns, and banks, extended almost beyond eye-reach. Between the flyers and the sun stretched isolated towers of cumulus, cast up as if erupted by the chaos below. The sunlight, filtering through this or that gossamer bulk, was scattered into every conceivable shade and monotone. And around the margins of the heaving billows the sun's rays played unhampered, unrestricted, outlining all with edgings of the purest silver. The scene was one of such extravagance that the brain was staggered with what the eye tried to register. Below the aviators, the shadow of their machine pursued them on white film like a grotesque gray bird of some supernatural region. The shadow followed tirelessly, gaining as the hour of noon approached, gaining still as afternoon began to gather, swell, and wane; and always it skipped from crest to crest down there just below, jumping gulfs like a bewitched phantom. It was so cold at this height that the aviators had to put on their heaviest garments, and they were content to open the windows only a slight way for ventilation. When darkness fell, they were still flying high, though at reduced speed, as John was afraid that a rate too much over schedule might cause them to overrun their destination before daylight could disclose its outlines to them. Every half-hour the pilot's helper checked up their position on the chart. Had this not been done from the very start of the trip, they never could have struck their ports with the accuracy they did, and disaster would have been the result, if not death to the crew.