When we take another look at earth I find that the pilot has been exact in timing our arrival at the important Boche base--too exact, indeed, for we find ourselves directly over the centre of the town. Only somebody who has been Archied from Plusprès can realise what it means to fly right over the stronghold at four thousand feet. The advanced lines of communication that stretch westward to the Arras-Péronne front all hinge on Plusprès, and for this reason it often shows activity of interest to the aeroplane observer and his masters. The Germans are therefore highly annoyed when British aircraft arrive on a tour of inspection. To voice their indignation they have concentrated many anti-aircraft guns around the town. What is worse, the Archie fire at Plusprès is more accurate than at any other point away from the actual front, as witness the close bracket formed by the sighting shots that greet our solitary bus. From a hasty glance at the station and railway lines, while we slip away to another level, I gather that many trains and much rolling stock are to be bagged. The work will have to be done under serious difficulties in the shape of beastly black bursts and the repeated changes of direction necessary to dodge them. We bank sharply, side-slip, lose height, regain it, and perform other erratic evolutions likely to spoil the gunners' aim; but the area is so closely sprinkled by shells that, to whatever point the machine swerves, we always hear the menacing report of bursting H.E. It is no easy matter to observe accurately while in my present condition of "wind up," created by the coughing of Archie. I lean over to count the stationary trucks in the sidings. "_Wouff_, _wouff_, _wouff_," interrupts Archie from a spot deafeningly near; and I withdraw into "the office," otherwise the observer's cockpit. Follows a short lull, during which I make another attempt to count the abnormal amount of rolling stock. "_Wouff--Hs--sss!_" shrieks another shell, as it throws a large H.E. splinter past our tail. Again I put my head in the office. I write down an approximate estimate of the number of trucks, and no longer attempt to sort them out, so many to a potential train. A hunt over the railway system reveals no fewer than twelve trains. These I pencil-point on my map, as far as I am able to locate them.