Sappers and miners at work on a tunnel, April 1915.

Sappers and miners at work on a tunnel under Hill 60, overlooking the Ypres salient, blown up April 1915′. Tunneling and mining operations were used to attack enemy positions by tunneling underneath them and then destroying them with explosive mines. Much of the tunneling on the Western Front was done by special Royal Engineers units formed from Welsh and Durham miners. From the collection of the former Buffs Regimental Museum. Stereographs consist of two identical photographs paired in such a way that when seen through a special viewing instrument, a stereoscope, they appear as a three-dimensional images. By 1899 the photographs were mounted on thick card that was given a slight curvature to increase the illusion of depth.