Page:Air Service Boys over the Rhine.djvu/172

162 would have accounted for Tom going to meet them, and Jack wondered greatly at his chum's action.

Still there was no way of asking questions just then, and Jack followed his friend. They sailed over the German lines at a good height, and Jack could keep Tom in view by noting the lights on his plane.

These were also seen by the Germans below, and the anti-aircraft guns began their concert, but without noticeable effect. None of the Hun airmen seemed disposed to accept a challenge to fight, so Tom and Jack had the upper air to themselves.

Below them the boys could see flashes of fire as the various guns were discharged; and at one point in the lines there was quite an artillery duel, the French batteries sending over a shower of high explosive shells in answer to the challenge from the Boches.

It was not until Jack had followed his chum back to Camp Lincoln, and they had made a landing, that a conversation ensued which was destined to have momentous effect.

"Jack, did you notice the peculiar colored lights away to the north of where we were flying?" asked Tom, as they divested themselves of their fur garments.

"You mean the orange colored flare, that