The boys leaned over the body of the machine, and scanned the earth below. It was too grand and inspiring for words. It was some time before they began to realize that the hangars were disappearing, and that the machine was now going forward in one direction. The country below was a confused maze of narrow yellow streaks, bordered by green and yellow spots, with innumerable rows of dark green and brown bands and patches, which they soon recognized as trees, while cottages and larger buildings dotted the whole landscape as far as the eye could reach. Alfred was the first to cast his eyes to the north. What he saw almost startled him. A dark vivid green spread to the horizon, blending with a pale mist, far, far away. "Look! look!" he cried. "That's the sea!" shouted Ralph. Tom smiled as he reveled in their joy. He pointed ahead, and the boys quickly turned. Far off, in the distance, they saw what seemed to be immense fields of snow. "What can that be?" asked Ralph. Alfred shook his head, and gazed silently, then turned toward Tom. "Can you make it out?" he asked Ralph. The latter shook his head. The machine went on for ten minutes more. Beyond the white fields something else arrested their attention; great clouds of smoke were observed. They were not clouds, and there was no fire visible on the earth. That was the second mystery. "I know what that is now," said Ralph. "What is it?" asked Alfred. "Tents, tents," said Ralph. "Yes, and that smoke must come from the big guns," said Alfred. Ralph turned his head toward Tom, and raised his cap. The latter knew that the boys recognized the nature of the scene before them. "That must be a battle," said Alfred, as he pointed to the great clouds of smoke. "Look way over to the left," shouted Ralph. "See that long, narrow road? There is something moving there." "Why, that is cavalry; sure enough. See, they are turning a corner in the road. That's plain enough," said Alfred. "I wonder if he is going to take us over the German lines?" queried Ralph. "And suppose something happens, and we are compelled to go down; we'll be in a nice fix," remarked Alfred. Ralph shook his head, and glanced back toward Tom. The latter, however, soon turned the machine. As he did so a dozen or more aeroplanes came into view. They noticed that the machine was going toward a field where a huge gas bag was moored near the ground. It was an observation balloon. Beyond were several dozens of flying machines drawn up in front of the hangars. Tom circled the machine around several times; the earth came nearer, and soon they observed a long stretch of green that seemed to invite them. In another minute they were several hundred feet from the earth, and they seemed to go faster and faster. "Whew! but doesn't it scoot now," said Alfred.