5924324 Amid bursting \'crumps\' with trench mortar ready, Seaforths watch through periscope for the Bosche\', World War One, 1915 circa (b/w photo) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: Amid bursting \'crumps\' with trench mortar ready, Seaforths watch through periscope for the Bosche\', 1915 circa. Stereoscopic photograph, World War One, Western Front (1914-1918), 1915 circa. Soldiers of the Seaforth Highlanders (Ross-shire Buffs, The Duke of Albany?s) in an entrenchment. Periscopes are positioned to view no-man?s-land and enemy positions beyond in relative safety. Two trench mortars are positioned in the entrenchment and rifles with fixed bayonets are also close to hand. 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. The photographs were mounted on thick card that was given a slight curvature to increase the illusion of depth.); by National Army Museum ; out of copyright.