In front, an observing biplane buzzed slowly to and fro, watching the effect of a mother[1] shooting at some mark behind the German lines. With the gun concealed in the trees, a gunner subaltern altered his range and direction as each curt wireless message flashed from the 'plane. "Lengthen 200--half a degree left." And so on till they got it. Occasionally, with a vicious crack, a German anti-aircraft shell would explode in the air above in a futile endeavour to reach the observer, and a great mass of acrid yellow or black fumes would disperse slowly. Various machines, each intent on its own job, rushed to and fro, and in the distance, like a speck in the sky, a German monoplane was travelling rapidly back over its own lines, having finished its reconnaissance. Behind it, like the wake of a steamer, little dabs of white plastered the blue sky. English shrapnel bursting from other anti-aircraft guns. Jim's gunner friend seemed to know most of them by name, as old pals whom he had watched for many a week on the same errand; and from him Jim gathered that the moment approached for the appearance of Panting Lizzie. Lizzie, apparently, was a fast armoured German biplane which came over his gun every fine evening about the same hour. For days and weeks had he fired at it, so far without any success, but he still had hopes. The gun was ready, cocked wickedly upon its motor mounting, covered with branches and daubed with strange blotches of paint to make it less conspicuous. Round the motor itself the detachment consumed tea, a terrier sat up and begged, a goat of fearsome aspect looked pensive. In front, in a chair, his eye glued to a telescope on a tripod, sat the look-out man. * * * * * It was just as Jim and his pal were getting down to a whisky and soda that Lizzie hove in sight. The terrier ceased to beg, the goat departed hurriedly, the officer spoke rapidly in a language incomprehensible to Jim, and the fun began. There are few things so trying to listen to as an Archie, owing to the rapidity with which it fires; the gun pumps up and down with a series of sharp cracks, every two or three shots being followed by more incomprehensible language from the officer. Adjustment after each shot is impossible owing to the fact that three or four shells have left the gun and are on their way before the first one explodes. It was while Jim, with his fingers in his ears, was watching the shells bursting round the aeroplane and marvelling that nothing seemed to happen, that he suddenly realised that the gun had stopped firing. Looking at the detachment, he saw them all gazing upwards. From high up, sounding strangely faint in the air, came the zipping of a Maxim. "By Gad!" muttered the gunner officer; "this is going to be some fight."