To get at the seat of trouble necessitated considerable disarrangement of the motor's parts. This consumed more or less time, and the minutes passing were jealously given up by the impatient Jack. But the boys worked fast, and finally all had been accomplished. Tom tested the engine, and pronounced himself satisfied, while Jack looked over the field ahead of them. "It's going to take us to Dunkirk without any further trouble, I give you my word for it, Jack," he said. "How long have we been here?" "Just one hour, lacking three minutes," came the prompt reply. "Then I'm safe," laughed Tom; "for I said within the hour. Come, pile aboard and we'll be off. Sure you examined the ground ahead, and saw to it we'd hit no bumps that might give us trouble?" "It's all right there, Tom; could hardly be better. But be sure you don't change from a straight course, because there's a nasty shell-hole, about ten feet deep, to the left. If we struck that--good-night!" "I notice you marked it with that pole, Jack, and I'll swing clear, you can depend on that." They had no difficulty in making a successful ascent. Once free from the ground, the plane's nose was again turned toward the southwest. Tom had long before marked out his course, and kept an eye on the compass as well as on his little chart. He knew they were heading for the Channel port as straight as the crow flies. The sun was getting far down in the western sky, and it was now necessary to shield their eyes when looking ahead, on account of the dazzling glare that at times threatened to blind them. The character of the country below had changed materially, Jack told the pilot, who seldom had a chance to look through the glasses, since his entire attention was taken up with manipulating the engine, watching its rhythmical working, and keeping the plane pushing directly on its course. "Heine didn't get a chance to ruin things here when he passed through, going to Paris and to his smash on the Marne," Jack explained. "Towns and villages look natural, as I see them, and they must have harvested crops in those brown fields. This is a bit of the real France, and entirely different from the horrible desert we've been at work in so long." The afternoon was wearing away. Jack frequently stared eagerly off to the west, when the sun's glowing face was veiled for a brief time by some friendly cloud. Several times he believed he could see something that looked like a stretch of water, but dared not voice his hopes. Then came a time when a heavier cloud than usual masked the brightness