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.