We got up to the lines the next day and had a fine view of the opposing trench systems for ten or twelve miles. Our box seat was on top of a hill just back of Messines ridge. We saw a duel between two aeroplanes, the explosion of a munitions dump, and no end of big gun firing but the officer who conducted us said that it was a dull morning. Our day on the hill was a clear one after three days of low clouds, and all the fliers were out in force. Almost two dozen British 'planes were to be seen from the hilltop, as well as several captive balloons. Although the English 'planes flew well over the German lines, they drew no fire, but presently the sky began to grow woolly. Little round white patches appeared, one against the other, cutting the sky into great flannel figures. Then we saw above it all a 'plane so high as to be hardly visible. Indeed, we should not have seen it but for the telltale shrapnel. These were our guns, and this was no friend. Now it was almost over our heads. It seemed intent upon attacking one of the British captive balloons, which could only stand and wait. The guns were snarling now. We were close enough to hear the anger in every shot. The shrapnel broke behind, below, above and in front of the aeroplane, but on it sailed, untouched, like a glass ball in a Buffalo Bill shooting trick. Yet here was no poor marksmanship, for at ten thousand feet the air pilot has forty seconds to dodge each shell. He merely has to watch the flash of the gun and then dive or rise or slide to right or left. Sometimes, indeed, the shrapnel lays a finger on him, but he whirls away out of its grip like a quarterback in a broken field. The guns stopped firing, although the German was still above the British lines. Somebody was up to tackle him at closer range. Where our 'plane came from we did not know. The sky was filled all morning with English fliers, but each appeared to have definite work in hand, and not one paid the slightest attention to the German intruder. This was a special assignment. When we caught sight of the English flier he had maneuvered into a position behind his German adversary. We caught the flashes from the machine guns, but we could hear no sound of the fight above us. The 'planes darted forward and back. They were clever little bantams, these, and neither was able to put in a finishing blow. Our stolid guiding officer was up on his toes now and rooting as if it were some sporting event in progress. Looking upward at his comrade, ten thousand feet aloft, he cried: "Let him have it!" The hostile attitude of the spectators or something else discouraged the German and he turned and made for his own lines. The Englishman pursued him for a time and then gave up the chase. The consensus of opinion was that the Briton had won the decision on points. "They've been making a dead set for our balloons all week," said an English soldier after the German 'plane had been driven away.