"That is the very thing I had in my mind this moment," responded the commandant. "It is most probable that such is the case. But stop; might that not be feet, eh, Captain?" "Not at all likely, for that would land us somewhere near the top of the hill, and I think you have plowed up that region pretty thoroughly," answered the captain. "Enough; if that battery isn't 300 meters to the right then we must make another guess. Get your ranges for 300 meters, and we'll pepper them tomorrow," said the captain in a decisive tone. "Before you go, boys, I want to say that you are certainly deserving of praise for your methods of observation; it is exercised in a direction that might be observed with profit by many others." The boys accompanied the captain and lieutenant to the temporary shed on the plateau next morning, after the final interview had taken place with the commandant. "The sight of the machines here almost makes me feel as though I ought to get back in the aviation service," said Alfred, as he walked around the machine and examined the new improvements that had been added since they were in that branch of the army. Promptly at eight o'clock the engines started and the machines began their flight. It was a beautiful sight to see them sail across the sunlit fields of France, for it was a lovely morning. "Ah! this will be a fine day to make observations," said the commandant, as the boys reached headquarters. "I should like to have you here to note the movement of the machines during their manoeuvers," he said, addressing the boys. Both Ralph and Alfred were accordingly supplied with strong field glasses to aid them in noting the events which would take place. The guns were silent as no orders had been issued for the resumption of the bombardment. Meanwhile, the airplanes had reached the zone directly above the questionable ground. They could be seen plainly by the boys, circling to and fro over the hill and to the south. In a half hour one of the machines rapidly ascended and started for the English lines. "Here she comes," said Ralph. "One of them is on the way." "But where is the other one? I haven't noticed it since they disappeared beyond the clouds," remarked Alfred. The airplane grew larger, and a single puff appeared. The order was given for the first round, and the hill shook with the reverberations. The airplane now circled around, while the guns kept booming, and after the first circle it flew back above the suspected area. Then it disappeared. The faintest trace of smoke appeared on top of the hill. The commandant saw it. "I suspect," he said, "that they have located some anti-airship guns on that point." "Yes, we noticed that yesterday," said Ralph. Suddenly, one of the airplanes came out of the gray cloud and Alfred was quick to announce the fact. "But why do we not get any signals from them?" asked the commandant.