Not only so but the road is blocked for the next six or seven hours for all traffic, and not only will guns go short of ammunition but more than one battalion of the German army will go short of food for the next twenty-four hours. For half an hour the guns continue to shell the rest of the column, which by that time has managed to get the undamaged motors away, by dashing blindly down any side turning that leads to anywhere, out of that terrible inferno. For a little while longer the observer continues to send cryptic messages back to headquarters, which have the immediate effect of altering and adjusting the range of the heavy batteries, until the whole convoy has dispersed sufficiently to prevent the waste of further ammunition. Modern warfare is like a game of chess, with move and countermove, and this applies just as much to war in the air as to warfare on land. Evidently this morning, however, the enemy have been caught napping. His air patrols have not yet been sighted. Surely he has had time to deal with the offender up there in the skies, who has been reading the secret of his lines, and the movements in his rear, or can it be that he is laying a trap for the unwary? So far the daring young adventurers have had it all their own way, but a surprise is in store for them. Meanwhile, however, they continue to circle around, noting half a dozen little things which Jock briefly enters on his memoranda sheet. A few photographs are also taken with the telescopic camera, for in reconnoitring the observer has noted some new lines of brown coloured earth showing up plainly against the green. Becoming suspicious he pointed them out to Dastral. Holding the joy stick between his legs, Dastral takes the glasses for a minute, then cries out, "New trenches, I believe!" "I think so, but we must make sure. I want a snapshot. Reserve trenches probably. Perhaps the enemy are thinking of falling back the next time they are attacked in force." "If so, we've got his secret. It's important; we must go down and see. Hold tight!" At that moment while the couple were intent upon the line of new trenches below, they failed to notice a little cloud that was coming up out of the eastern horizon. Till now it had been bright and clear, as it often is at the break of dawn, but the first little cloud, no bigger than a man's hand, had arisen. And it was in that cloud that the danger lay. Heedless, however, of this little thing, and willing to take some deadly risks to get the precious photograph, which might prove to be the final link in some theory held at headquarters as to the position on the enemy's front, they ignored the coming danger. Putting forward the controlling gear the hornet dipped her head, and made a graceful nose-dive at a terrific speed, losing in fifteen seconds that which she would shortly very badly need, namely, her altitude.