Of a sudden he straightened up, uttering an exclamation of surprise.
"Lieutenant!" he shouted. "Look here!"
The lieutenant jumped out of the tractor, and the others followed him on the run to where Joe and Frank were gazing off down into the opposite valley.
Two, perhaps three, miles away, a winding, twisting line of black against the snow was pushing its way laboriously around the mountain base.
"Germans!" exclaimed Lieutenant Mackinson. "Wait until I get my field glasses, but do not stand where they might see you with theirs."
From positions within the clump of trees the lads watched the line spread out and slowly but surely forge its way ahead. The lieutenant returned with his glasses.
"At least ten thousand of them," he announced at last, after gazing down at them for fully a minute. "And nobody knows how many more behind. We must notify the camp at once."
He ran back to the tractor, followed by all but Jerry, who remained to observe the enemy's further movements.
In two or three minutes the wireless operator at headquarters signaled back for them to go on with the message.
"About ten thousand enemy troops proceeding through eight inches snow, bound northwest around eastern base of mountain," Lieutenant Mackinson's message ran. "Am observing and will report progress. Any orders?"