The ranges of hills--some of them dignified enough to be termed "mountains"--which they crossed necessitated their flying high. They were generally at an altitude of two thousand feet and the rarefied atmosphere so far above the earth was cool, anyway. Since leaving St. Thomas, on the bank of the St. Lawrence, they had averaged eighty miles an hour, and before moonrise they were cognizant of the fact that they were approaching a great sheet of water. "St. James Bay, the lower part of Hudson Bay," Professor Henderson explained. Soon the moonlight shimmered upon the waves beneath them. Jack, who was guiding the craft, deflected the wings and they slid down the airways toward the water. They traveled all night over this great inland sea, at times so close to the surface that the leaping waves sprinkled them with their spray--for there was a stiff breeze. A gale broke in earnest over the Hudson Bay territory that day, and despite the efforts of the voyagers they could not rise in the _Snowbird_ above the tempest. Had there been solid ground beneath them they could easily have descended and remained upon terra firma until the storm was past. This gale was favorable to their course, but it gripped them in its giant grasp and hurled them on into the northwest at a speed that imperiled the safety of the flying machine each moment. There was no sleep for any of the party now, and Washington White came pretty near (as Jack said) "making good his name in his face"--for if ever a darkey of Wash's ebony complexion turned pale, the professor's servant did so at this juncture. On and on they were driven hour after hour. Scarcely a word was spoken the entire time. There was no cessation of the gale. The great body of water was passed and they knew that there was land beneath them again. But each time they tried to descend they found the storm near the earth-crust far heavier than at the upper levels. To descend through the belt of the storm might partially wreck their flying machine and the professor knew, by the study of his recording instruments, that they were passing over an utter wilderness in which no help could be obtained and from which, should they be wrecked, they could not escape before the rigorous Arctic winter set in. Hour after hour they drove on. The speed of the _Snowbird_ at times, when driven by the full force of the gale, had mounted to one hundred thirty miles an hour. Great Slave Lake was far south of their route; yet the professor told them that, had it been clear, at the altitude they traveled, they could have seen and marked this great body of water.