Billy sat like a statue in the machine, facing a reserve force of grim, gray-garbed veterans standing at attention. The front rank soldiers eyed the boy curiously, no doubt wondering that one of his years should be serving in the capacity of a full-fledged military aviator on a mission so supremely perilous. Billy could not understand what Colonel Muller was saying to the commanding officer of this regiment, but he could see the effects rippling through the serried lines, a stiffening of attitude, a closer grip of rifle stock and squaring of shoulders. The column, solid and compact, the German practice of close formation, moved with clockwork precision down the field to back the general charge against the living wall that barred the way. "Charge! Charge!" The cry from a thousand throats. The forces mixed in a struggling, swaying mass, with indescribable noises, the clashing of steel and the squealing of horses, for cavalry had joined the fray. Billy jumped out of the machine into the dusty road, the sole spectator there of the conflict that raged but a half mile distant. Colonel Muller had taken to horse and was riding furiously to rally incoming reinforcements for the gray column. A rattle cut into the sound ruck--the machine guns of the Germans had turned loose, and men were mowed down like ripened corn. But fainter now in Billy's ears grew the roar of violent contention, alternate advance and retreat serving to shift the tide of battle further northward, and finally stemmed by the final demonstration of the day at Soissons bridge. Barring the occasional wild gallop of a riderless horse down the road, the young aviator saw no signs of life about him, and he was too far away to hear the groans of the wounded on the sodden field now enfolded by the gathering gloom of evening. "I wonder if the colonel has forgotten that his carriage is waiting," thought Billy, trying a bit of mental cheer to relieve the strain of his trying position. The colonel, however, had not lost his memory along with his hat, for even then a foam-flecked horse was bringing him back to the driver of his aërial chariot. Mud-bespattered from head to foot, he sent a hearty hail ahead of the pounding hoofs of his weary mount. "Ahoy, my stranded mariner: is supper ready?" That reminded Billy of a decided vacancy under his belt, but the glad sight of the colonel was the best tonic for a drooping spirit. "We will wheel this airship out of the way for a spell and have a bite to eat in the trenches." Concealing the biplane behind a clump of bushes the colonel gave Billy a hand-up, and the horse cantered away with its double burden in the direction of the slopes. It was about 7:30 when the colonel and Billy climbed over the slippery slopes to the line of reserve trenches, lowered themselves into one of these holes in the ground, and it was evident that the occupants knew how to convert a ditch into a home.