The main characteristic of this period was a continual and savage bombardment of the British infantry by the German artillery. To the infantryman this is a most trying and aggravating form of warfare, as though his own guns may be supporting him by giving the German infantry similar treatment, he has no adequate means of ventilating his own feelings towards the enemy, and can but passively endure the bombardment. The troops in the front line on the right had their backs to the river Scarpe, flowing south-east, only a few hundred yards in rear of them. This river is in itself only some thirty feet in breadth, but flows in the main through swampy marshlands. In advance of the foremost trenches lay the village of Roeux, masked on its western edge by a hanging wood which sloped down towards the river. North-west of Roeux was a small but conspicuous copse standing on high ground, called for some obscure reason Mount Pleasant. Due north of Roeux lay the now famous chemical works--a large factory surrounded by numerous buildings that had been used as workmen's dwellings, offices, &c. Diagonally across the left of the position ran the Arras-Douai railway, passing through a deep cutting on the summit of a high rise about a thousand yards in rear of the chemical works. This rise was known as Greenland Hill. It was the most prominent feature in the landscape, and overlooked all the neighbouring country-side. It possessed the peculiarity of having its summit, which was actually south of the railway, shown as being north of the railway on the official maps. On it were a large quarry and two woods, named Hausa and Delbar, which commanded extensive views, observation posts in the tree-tops covering a vast expanse of the surrounding country. The whole feature formed an extensive and lofty plateau, which stretched almost to the Scarpe, the ground falling down to the water's edge in a steep slope. This slope, being covered with trees, afforded the enemy a good covered approach along the banks of the river. The position as it stood was one which could not be allowed to remain. A successful attack from the Germans would force our troops into the Scarpe. Moreover, there was little room in the confined area between the front line and the river in which to manœuvre troops to resist attack. On the other hand, if a force moving over Greenland Hill and north of it could strike at Plouvain, the Germans between Plouvain and the chemical works would find it almost impossible to extricate themselves. Orders were therefore issued for an attack to be prepared with this intention. In the circumstances, one of the earliest considerations was the gaining of ground by minor enterprises, so as to extend the area in which troops could be assembled for the attack. [Illustration: MAP V.--THE CHEMICAL WORKS, ROEUX.] On 18th April the front line was extended southwards by the occupation of a portion of sunken road running parallel with the Scarpe about 300 yards east of it.