Bridge 52, Calder Aqueduct and weir, Lancaster Canal

Bridge 52 is an aqueduct that carries the Lancaster Canal over the River Calder, along with a weir on the river. It was built in 1797 when the canal opened, designed by engineer John Rennie. The structure is made of sandstone, with later alterations in concrete.

The aqueduct supports the canal and towpath above the river and features rock-faced sandstone below the parapets. Both the upstream and downstream faces of the aqueduct are curved to enhance its strength. The western parapet is made of large sandstone blocks set on edge, two courses high. The eastern parapet, which is set back about 5 meters from the canal's edge, is constructed of coursed dressed sandstone and curves around upstream on both sides of the river. Parts of the eastern parapet have been partially rebuilt in concrete. Upstream of the aqueduct, there is a weir that is built continuously with the aqueduct. This weir consists of large sandstone blocks shaped with a rounded profile along its crest and stands approximately 1.5 meters high. It was designed to lower the riverbed beneath the canal. The river flows under the canal through a single elliptical arch.