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.
They grasped the body of the car, while it seemed to fairly sizzle through the air. Closer and closer the earth crept up toward them. They felt that it would be necessary to hold fast when the shock came. The next sensation was most peculiar; the body of the car began to rock up and down; the din of the motor had ceased, and they were riding on the earth.
CHAPTER IV
TRENCH WORK WITH THE BRITISH FORCES
Everyone seemed to know Tom, as he was heartily greeted on all sides. The appearance of the boys, however, was a puzzle to the group of aviators.
"Let me introduce my friends, Ralph and Alfred, genuine American boys, who were with the Belgians in their great fight from Liege to Antwerp," said Tom.
"How did that happen?" asked one of the men, as he grasped their hands.
"We were on the spot when war was declared, and we just pitched in and helped them out," replied Ralph.
"Were you in any battles?" asked another.
"Oh, in a dozen, or so," answered Alfred.
"Good boys!" shouted several.
"How did you happen to get here?" asked the first interrogator.
"We came over with the Belgians, from Antwerp," said Ralph.
The foregoing information was enough to introduce the boys, and they were gratified to find several other Americans in the party.
The reception was cut short by the peculiar antics of a huge Farman machine, which was approaching in an erratic manner. It seemed to dart back and forth, and swing around in short circles, as though wounded.
"Something is the matter with Le Clere," shouted Tom.
At that moment the machine darted toward the earth, and the boys held their breaths at the anticipated calamity. Fifty feet from the earth the machine righted itself, and swooped upward, then, with a vicious plunge, it went down and struck the earth, the crash being plainly heard, although it landed more than five hundred feet from where they stood.
Every one on the ground rushed toward the fallen aviator. Before they reached the scene, two men extricated themselves, and stood on the debris.
"What was the matter?" asked Ralph.
"Look at the holes in the wings," said Tom. "That tells the story; pretty well riddled."
"Are you all right?" shouted one of the men.
"Yes, but that was a dandy fight, and we brought him down," replied Le Clere, a daring Frenchman, who handled the machine gun.
The Gnome motor was lying on the ground twenty feet from the wreckage. One of the planes was tilted up at an angle, and was uninjured, but it carried the marks of twenty holes, through which the sunlight streamed.
"That will give you an idea of the fascinating work we are engaged in," said Tom, pointing to the bullet marks. The body of the machine was wrecked, and the fuselage a mass of splinters. It was, indeed, a mystery how the two flyers escaped without injury.
"What will they do with the machine?" asked Alfred.
"They'll build up another out of it in two days," said Tom.
"The Germans are marching west and south of Roubaix," said Le Clere. "They have already reached Mons, and are going straight toward Paris."
The boys looked at each other in amazement. It seemed as though their trip to Paris would be interrupted, after all. Tom seemed to read their thoughts.
"How far is it to Mons?" asked Alfred.
"About fifty miles south," said Tom.
"And what is the name of the town which we saw before we came down?" asked Ralph.
"Lille," was the response. "But we must be going back," continued Tom. "We are going to move south in the morning, and I have a few things to pack up."
After bidding good-bye to every one, they climbed into the airplane, and those present gave the boys a cheer, as the machine glided forward. Tom had promised to give them an hour's flight, and it was now four o'clock. They had heard about taking observations, while on the grounds at Lille, and they busied themselves in trying to do work of that character. How small the houses were! They could see little creeping things, that soon evolved themselves into horses and wagons, but they seemed unreal.
The flight to Lille covered a distance of forty-five miles, and it took them an hour. It didn't seem that they could have been aloft half of that time. Now, on returning, the novelty had worn off, and they were so much interested that they forgot to look at their watches until the deep blue haze, which betokened the approach to the sea, aroused them.
"Why, it's past five o'clock," said Ralph. "Tom was going for an hour's flight only," said Alfred.
"He just said that in fun, I suppose," replied Ralph.
After alighting the boys did not know how to fully express their appreciation of Tom's kindness for the great treat, and they inquired whether they could not be of some service to him, as they were only too anxious to help him out in any way that would be useful.
"Why, no; I don't know what I can put you at," replied Tom. "Of course, there's always