and entered the famous French school at Pau. Then, having mastered the science of flying sufficiently to be sent to the front, they had joined the Lafayette Escadrille, as related in a previous volume entitled "Air Service Boys Flying for France; or The Young Heroes of the Lafayette Escadrille."

Tom in particular seemed to have a great career ahead of him, unless some unfortunate accident, or possibly a Teuton pilot, cut it short, as had happened in the cases of Rockwell, Prince, McConnell and Chapman. Every one knew he possessed genius of a high order, and that it would not be long before Tom Raymond might anticipate gaining the proud title of "ace," which would indicate that he had defeated five enemies at different times, and put them entirely out of the running.

Tom was already a corporal in the French service, and expected before a great while to be given the privilege of wearing the chevrons of a sergeant. Jack had not progressed so rapidly but was doing well.

And now to return to the young aviators during their walk.

"I reckon we've gone far enough, Jack," Tom remarked presently. "Our friend Jean may have been telling the truth when he said there were still a few bunnies left alive in this war-racked section of country, but I can see they've got the good sense to stick to their burrows during the daytime. We won't be burdened with our bag of game on the return trip."

"Yes, that's always the trouble, when you go out after rabbits and haven't any hound along to get them up and bring them within gunshot," grumbled Jack.

"But we've had a good walk," returned his companion; "and for a time we managed to get away from that terrible explosion of shells, and big-gun firing. We ought to be thankful for our little time off, Jack."

"Oh! I'm not really complaining," remarked the other young aviator, with a whimsical expression on his good-natured face. "But don't you know I hate to go back without having fired even one shot." He stopped short and pointed upward. "Hold on, Tom; there's some kind of bird going to pass over right now! Crow or anything, please bring it down! I'll promise to eat it, no matter what it is."

Laughingly Tom threw the gun up to his shoulder, and the next instant the report sounded. It seemed almost contemptible, after listening to the roar of those monster shells exploding for so long.

The bird fell fluttering in a heap. Tom evidently was a fair marksman, for it had been moving swiftly over their heads at the time he fired. Jack ran forward and picked the game up. As he did so he gave utterance to exclamations that naturally excited the curiosity of his chum. So Tom, after reloading his gun with a fresh shell, waited for Jack to rejoin him, which the other did, his face full of mystery.

CHAPTER II
THE WINGED MESSENGER

"What do you call this, Tom? A queer sort of crow, I'd say. Looks more to me like the blue-rock pigeons Sam Becker used to raise at home," and so saying Jack held up the still quivering bunch of feathers.

Tom took one quick look, and then a startled expression flitted across his face.

"Just what it is, Jack!" he hastened to say. "A homing pigeon in the bargain! You can tell that from the bill and the ring around the eyes."

Jack in turn became aroused.

"A homing pigeon, is it?" he ejaculated. "Why, birds like that are used for carrying messages across the lines! Some of our airplane pilots have told me that sometimes they take a French spy far back of the German front. When he had made an important discovery he would write a message in cipher, enclose it in a tiny waterproof capsule attached to a ring about the pigeon's leg, and set the bird free. Inside of half an hour it would be safe back in its loft, and the message on the way to French headquarters."

He lifted one limp leg, and then the other.

"Look here, it's got a message, as sure as anything!" Jack exclaimed.

Tom leaned forward and took the bird in his hand, dropping the gun meanwhile. He carefully took off the gelatine capsule, and from it extracted a delicate piece of tough paper, which he spread open. There were a series of strange marks on the paper, of which neither of the air service boys could make anything.

"Looks like hieroglyphics, such as you'd expect to find on an Egyptian tomb or in the burial places under the pyramids," complained Jack, after he had stared at the lines in disgust for a brief period of time.

"It's a cipher of some kind," explained Tom, seriously. "With the key all this would resolve itself into some sort of communication, I suppose, connected with valuable information concerning the French armies here at Verdun."

"Then it was made by a spy!"

"No question about that part of it," came the ready reply.

"This carrier pigeon with this message, was on its way across to some point in the rear of the enemy line when you fired, and brought the poor little thing down in a quivering heap, I'm sure that's it," continued the other.

"Yes. And so after all it's turned out to be a lucky thing you chanced to see the bird coming along, Jack, and begged me to knock it down so we could show some sort of game when we got back to camp."

"What ought we do with this message?" asked Jack, accustomed to depending on his more energetic chum in many cases; though when left to his own resources he could think for himself, as had frequently been proved.

"I shall see that it gets to French headquarters, with an account of the singular way we ran across it," Tom told him.

"Do you think it would be possible for any one there to translate this cipher of the German secret code?"

"Why not?" Tom demanded. "They are clever people, these wideawake French, and I shouldn't be at all surprised if they turned this incident to some good use."

"How?"

"Oh, it could be done in many ways. Suppose they found the key to the code. Don't you see how a fictitious message could be sent on in some way, if they could bag another pigeon from the same coop? They might even coax the Germans to deliver a furious attack at a supposed weak place in the line, which would of course be heavily guarded."

"That would be something worth while!" exclaimed the other with glowing eyes. "Lead them into a trap, where they would be mowed down like ripe grain, terrible as that sounds!"

"Yes, that's the idea I had in mind. But it would depend on several things. First of all would come the successful solving of this cipher code."

"Yes, and then the finding of another homing pigeon," added Jack. "I wonder if the fellow who released that bird could have a lot more of the same kind hidden away somewhere around back here."

"I was just going to suggest that we take a turn toward the south, and look around a bit before going back to camp. Do you feel equal to it, Jack?"

"What, me! Tom? Why, I'm as fresh as a daisy! This business has made me forget there's such a thing as getting tired walking."

"Let's see, we stood here when I fired," continued Tom reflectively, "and you walked straight to where the bird dropped. That would make the direction due northwest by southeast. How about that, Jack?"

The other took a survey, and then pointed with his hand.

"When I saw the bird coming first of all, Tom," he finally remarked, "it was just showing up over that clump of trees killed by gunfire. And it was heading as straight as can be for us."

"Yes," Tom went on to say, "because a homing pigeon on being released will rise to a certain height and take its bearings.