By Brook Culvert
A small bridge or culvert over the By (or Box) Brook, 225m east of the East Portal of Middlehill Tunnel and 250m to the south-west of Box Mill, Box, Wiltshire.
Designed by Isambard Kingdom Brunel and constructed c.1840.
By Brook formerly powered Box Mill, a corn mill. The bridge was built to carry the line and a footpath over the By Brook. The south face is impressively architectural for a structure of this scale, probably due to its position in the landscape as visible from the village across green open space. Unusually for a railway bridge, this face is unaltered. The more plain north (Up) elevation has had some alterations.