5925173 Consulting a map, 1917 (lantern slide) by Unknown photographer, (20th century); National Army Museum, London; (add.info.: Consulting a map, 1917. Lantern slide, World War One, Western Front (1914-1918), 1917. A motorcycle despatch rider and a colleague consult a map while wearing their gas masks. The British Army developed a range of gas helmets based on fabric bags and hoods that had been treated with anti-gas chemicals. Improvements continued to be made and by the middle of 1916 the small box filter respirator was also in circulation. This design gave protection against the different gases in use. Despite this, during the war the British Empire suffered over 180,000 gas casualties. From a box of 80 lantern slides.); by National Army Museum ; out of copyright.