"Why are they doing that?" asked Alfred, who overheard him.

"Oh, they'll get the range in time," he replied.

"There's the first airship, to give them a pointer," said the corporal, as an airplane appeared in sight.

"Two of our machines are coming up," shouted Ralph. "Now there'll be a fight."

Ralph was right. The two English machines steered straight for the oncoming Fokker, the latter veering to the left in time to prevent too close a meeting. Within a minute three more German machines came into sight, their appearance being answered by four of their own machines, which came up from the rear, and sailed straight across above them to the German positions on the crest of the hill. They were much higher than the German machines, the reason being that the enemy had a number of anti-airship guns to meet any flyers who dared to cross the line at a low alt.i.tude.

It was, indeed, an interesting sight to observe the numerous airplanes, which were employed by the two forces. They seemed to be flying back and forth in the utmost confusion, and, frequently, puffs of smoke would indicate that they were firing at each other.

The corporal with whom the boys talked seemed to be unusually well informed, and quite a number of the soldiers addressed him for information.

"How do they recognize an enemy?" asked Ralph.

"Oh, that's an easy matter," he replied. "I suppose the flyers in the air do it on the same principle that we are in the habit of recognizing automobiles. Why, I have a lad not ten years old who can tell the make of almost any auto the moment he sees it. Generally, if the make of the plane is similar to those attached to the aviator's side he is able to recognize it by the special mark it carries."

"What mark do you mean?" asked Alfred.

"Why, the English and the French mark is in the form of a circle, generally three, each circle being of a different color," was the answer.

"There is one,--why, it's red, white and blue," said Ralph.

"That's correct,--those are the colors of the Allies."

"What are the German colors?" asked Ralph.

[Ill.u.s.tration: _Allies' Distinguishing Mark_]

"Black and white," said the corporal.

"Oh, yes, they have a cross," said Alfred.

"Yes; a cross in imitation of the iron cross, so far as its shape is concerned," he answered; "that is, a black cross on a white field."

The company marched back to the line. During the next half hour there was nothing but expectancy, waiting, waiting,--that most trying thing for soldiers, who know that a battle is impending. Then a hundred feet to their rear there was a terrific explosion, which startled every one.

This was followed by others, but none reached the trench line.

Thus, during the whole day, there was an exchange of artillery, the greatest damage being done to those in the rear who were trying to get to the front.

"With the long range guns the great danger isn't always with the fellows in front," said the corporal.

[Ill.u.s.tration: _Black Cross on German Flyers_]

At four that afternoon the company was startled by an order to leave the trenches and fall to the rear. Every one cast questioning glances, but the knapsacks and rolls were quickly seized, and within ten minutes they were in line with the regiments to the right and the left. There was no hurrying or disorder.

"I wonder why we are going back?" asked Ralph.

"I suppose it's our business to retreat," returned the corporal.

They marched fully a mile to the rear, pa.s.sing on the way at least half a dozen lines of trenches, which had been thrown up since the boys covered the ground the night before. Every trench line was filled with soldiers, those in the front being the first to retire. On the way they saw how the great sh.e.l.ls had played havoc with many of the works.

They again crossed the river, and at six o'clock that night a new line was formed, and the spades and picks were again brought into use. The booming of cannon was incessant, and, although they tried to get some sleep after midnight, they were frequently aroused by the marching of troops. At daylight they were again marched out of the trenches, and a quarter of a mile from the last trench halted to partake of breakfast.

The march was directly south, and at noon they reached a town of some importance, called Chauny. They went through without halting, crossed the river Oise, and at four o'clock halted on the eastern banks of a stream, which flowed northwardly. Here they waited for orders. A picturesque bridge spanned the stream, and the boys wandered across.

West of the river was a broad expanse of country, perfectly level, and thousands of people from the nearby villages lined the road, all crossing to the west.

All were excited, and seemed to be going toward the narrow road, which led to the left, and, naturally, the boys followed the movement of the crowd. Their curiosity was soon satisfied, for beyond was a sight which caused their hearts to beat with joy. Fully a dozen airplanes were drawn up in line, and the boys started forward on a run that seemed to instill the same activity in many others present.

"There's a Morane," said Ralph.

"Yes; and that's Tom getting out of the machine," shouted Alfred, as they rushed up and greeted Tom, who looked at them in astonishment.

"And how did you get here?" he inquired.

"Came over with the troops," explained Alfred.

"With what troops?" he was asked.

"Don't know," answered Ralph, "but they are from Ess.e.x."

"Well, we've been on duty for a day directly over the lines east of St.

Quentin," said Tom.

"Did you have a fight?" asked Alfred.

"I should say we did," answered Tom. "Brought down two, at any rate, and it was pretty hot for about an hour. So you are on your way to Paris; sorry you didn't get back before we started," he added.

"We got to the grounds several hours after you left," said Alfred.

"Glad you came; we can put you up, if you are willing," remarked Tom.

"Thank you for the invitation; we helped them on the trenches and have done considerable marching, so it's better than going back to camp,"

said Ralph.

The boys were up early in the morning, but didn't have the least idea what steps to take to continue their journey. Everything in the way of transportation was reserved for the troops. Thousands of people were leaving their homes, and people with household effects, mounted on all sorts of conveyances, were noted on all sides, although at this time the Germans were not within ten miles of the river. The nearest railway to the south, which ran east and west along the southern bank of the river Aisne, was fully ten miles distant from this point.

Tom was on hand early, and greeted the boys most affectionately.

"I have been thinking I might be able to help you out a bit," he said, after a little talk. "We are ordered to the station near Villers-Cotterets, and that's only forty miles from Paris."

"How can you help us?" inquired Ralph excitedly.

"Probably I can give you a lift in the machine," he said.

"How far is that from here?" asked Alfred.

"Twenty miles," replied Tom, and the two boys looked at each other hopefully, as he left them.