Down they went, flying comparatively low but at great speed in order to offer less of a target to the gunners below them. And, following instructions, each pilot noted carefully the section of the German trenches beneath him, and the area back of them. They were seeking the big gun.
But, though they looked carefully, it could not be seen, and finally when one of the French machines was badly hit, and the pilot wounded, so that he had to turn back toward his own lines, Cerfe gave the signal for the return.
In all this time not a Hun plane had come out to give battle. What the reason for this was could only be guessed at. It may have been that none of the German machines was available, or that skillful pilots, capable of sustaining a fight with the veterans of the French, were not on hand just then. However that may have been, Tom, Jack and the others, after firing a few rounds from their machine guns at the trenches, though without hope of doing much damage, turned back toward Camp Lincoln.
"Well, then you did not discover anything?" asked Major de Trouville, who had been transferred and given the command at Camp Lincoln.
"Nothing," answered Jack.
"If it's in the section we covered, it is well hidden," added Tom.
"And I think, don't you know," went on the Englishman, Haught, "that the only way we'll be able to hit on the bally mortar is to fly low and take photographs."
"That's my idea," said the major. "If we take a series of photographs we can develop them, enlarge them, if necessary, and examine them at our leisure. I had thought of this, but it's a slow plan, and it means—casualties. But I suppose that can't be avoided. But I wanted to try the scouting machines first.
"After all, the taking of photographs from the air of the enemy trenches and the land behind them is a most valuable method of getting information," he continued.
Men, specially trained for such observation work, examine the photographs after the aviators return with the films, and they can tell, by signs that an ordinary person would pass over, whether there is a new battery camouflaged in the vicinity, whether preparations are under way for receiving a large number of troops, or whether a general advance is contemplated. Then measures to oppose this can be started. So, Major de Trouville was right, photography forms a valuable part of the new warfare.