Beneath the surface of one of Scotland's most enduring crossings, time and moisture have been quietly at work. The Forth Road Bridge—open since 1964 and woven together by nearly 24,000 steel wires—has been found to carry corrosion not at its edges but at its core, with engineers estimating a strength loss of 8 to 10 percent in its main support cables. In response, pressurized dry air is now being pumped through those cables in a continuous effort to arrest what the elements have begun. It is a reminder that the structures we rely upon most are not immune to the slow, invisible forces that act