If they might see nothing of the battle going on behind the ridge, they had grandstand seats for the theatrics of war in the air, staged on the background of the blue ceiling of heaven. I was not to see the like of this scene again in such bright sunlight. The most jaded veteran never failed to look up at the sound of machine-gun firing, which signaled that the aces might be jousting overhead. Would one be brought down? There might be only an exchange of bullets between planes in passing; then one might turn to give chase to the other; or both begin maneuvering for advantage. In shimmering flashes the sunlight caught the turning wings of planes that tumbled in a "falling leaf" when at a disadvantage, caught the wings of planes that were crippled and falling to their death. Duels were forgotten when a German plane with no Allied plane across its path swept down toward the huge inflated prey of an observation balloon. His telephone told the observer in the basket that it was time to take to his parachute. The sight of the figure of a man, harnessed to a huge umbrella, leisurely descending from a height of a thousand feet, divided attention with watching to see whether or not the gas within the thin envelope overhead broke into a great ball of flame. If not, it was brought down to take on its passenger again; and it could be lowered with incredible rapidity for such an immense object, as the wire which anchored it was reeled in on the spinning reel on the motor-truck. There was something very modern and truly American about a motor-truck in a column of traffic towing a balloon. Most fortunate of all the spectators were the men with machine-guns for aërial defense mounted on trucks. They both observed and participated in the game. Many of them were in action for the first time with a new toy. They did not propose to miss any opportunity to make up for having come late into the war. "Haven't you learned the difference between an Allied and a German plane? You're shooting at an Allied plane," an officer called to a machine-gunner. "Yes, sir," was the reply, and he stopped firing. "Why didn't you tell him you couldn't hit it anyway?" remarked a passing wounded man, after the officer had passed on. "But don't worry. If they miss the plane, the bullets can still hit somebody when they fall." Entranced as they were by the spectacle, all the men who had to do with the moving of the wheels of all the varieties of transport which overflowed the roads were only the more eager to press forward. The air was not their business. Their duty was over the ridge toward the front. The artillerists had particularly appealing reasons for impatience, as we shall see. They were using rugged language, which relieved their steam-pressure without changing the fact, which was being burned into the consciousness of the whole army, that as surely as a chain is no stronger than its weakest link, a road is no stronger than any slough which holds up traffic.