Railway construction stage 3, France, during World War I. This photograph shows two officers standing on the top of a railway viaduct. The viaduct, which crosses a wide shallow valley, is built of cross-braced, squared timbers bolted together. One soldier is standing inside the framework, others can be seen in the distance. Railways were one of the most efficient ways of moving troops and supplies towards the Front. [Original reads: 'OFFICIAL PHOTOGRAPH TAKEN ON THE BRITISH WESTERN FRONT IN FRANCE. Rapid railway construction in France. Broad gauge railway at one mile a day. A trestle bridge completed in one week.'].