THE speaker on February 4 was David de Haan of the Ironbridge Museum Trust, an organisation established some years ago to maintain the original structures of the area together with the famous bridge.

Prior to the restoration of the bridge, begun in 1972, considerable research was done regarding its original construction. Close examination revealed the ribs and braces that support the bridge were not all identical in size and shape.

To some extent, that may date back to the original construction but earth movements, including earthquakes, are also responsible. These irregularities were shown up by a photochromatic survey which plots the parts of the bridge in different colours by means of computer graphics, something that is impossible from an ordinary black and white photograph.

In carrying out the restoration, authenticity was important and one item that had to be considered was the stonework at the ends of the bridge, some of which needed attention.

In order to match the original, samples were sent to various quarries and a quarry only 200 yards from the bridge gave a perfect match, which would indicate this is where the material first used originated.

The talk was illustrated with slides and civil engineering diagrams.