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."