Continuing on past the Leawood Pump House, the Cromford Canal crosses over the river Derwent by means of the Wigwell aqueduct (which is also known as the Leawood Aqueduct and the Derwent Aqueduct). This triple-named aqueduct is an 80 yard span which carries the canal 260 feet above sea level and 30 feet above the much faster flowing waters of the Derwent; from where it looks surprisingly like an ordinary bridge - click here to see.
During construction of the Canal, two aqueducts caused problems. In January 1792, the (now demolished) Amber River aqueduct failed and, in August 1793, the spandrel walls of this aqueduct parted, causing a split along the length of the arch. In his report, William Jessop, the main engineer, blamed the Crich lime being used in the morter, claiming that it was unusually pure and had delayed the setting of the mix. Later engineers are of the opinion that the spandrels were simply too thin to withstand the horizontal forces imposed by the water. To rectify the problem, Jessop had the arches partially demolished and steel bars installed as reinforcement. This he did at his own expense, so it is probably fortunate for him that the finished canal did prove a financial success (and, to his credit that the aqueduct is still in good working condition to this day)!
PS: Lesson learned this morning ... how to spell aqueduct!