The outpost line (shown by the dotted line in Sketch C) extended from 1000 yards south of Avion to the north-west corner of Lens. Behind this ran several other lines, covering altogether a depth of three miles. The Souchez river and the canal which ran by its side formed a natural boundary between the two sectors. Two spurs known as Hirondelle Ridge and Hill 65, standing up on either side of the river, formed bastions to the various defensive lines and gave observation over a large extent of ground. About two miles west-south-west of Avion rise the slopes of the northern end of Vimy Ridge, giving a magnificent view over many miles of the open country to the east. An O.P. on Vimy Ridge was always occupied, for though it was too far back for observation of artillery fire it was useful for obtaining information of movements behind the enemy’s line, and for spotting flashes. [Illustration: LENS AND AVION, 1918. Sketch C.] East of Avion the enemy occupied the high railway embankment which ran in the form of an oval to the north of Méricourt and back. This was known as the Bull Ring. For a long time the Canadians had tried to get a prisoner from this place, but had never succeeded. The Division carried out many raids here with the same object, but although prisoners were taken from advanced posts on this front, it was only rarely that the Bull Ring itself could be entered. It was indeed a very formidable position especially at the Avion end, where the south-west face of the embankment consisted of a high and solid wall of masonry. Here the only point which gave any hope of success was a gap near the north-east corner of Avion, where the railway bridge over the road had been broken, leaving a gap in the embankment. The other railway lines converging at this point also ran on embankments which were held by the enemy as advanced positions. Between Avion and Lens a large area of ground had been flooded sufficiently deeply to prevent any advance by either side on that front. This flooded area was completely overlooked by the Green Crassier, a large slag heap, which formed part of the enemy’s defences. North of the Souchez river the whole of the ground in front of the line was a mass of ruins, the remains of the continuous succession of mining villages which encircled Lens. Behind our line the mining town of Lièvin was still standing, but every house had been damaged by shells. South-east of Lens the horizon was bounded by the houses which stood on the crest of the Sallaumines Ridge.