Bridge 52, Calder Aqueduct and weir, Lancaster Canal

An aqueduct carrying the Lancaster Canal over the River Calder together with a weir on the river. It was built at the time of the canal's opening in 1797 by the engineer John Rennie and is constructed of sandstone with later alterations in concrete.

The aqueduct carries the canal and towpath over the river and is built of rock-faced sandstone below the parapets. Both the upstream and downstream faces of the aqueduct are curved in plan to strengthen the structure. The aqueduct's western parapet is built of large sandstone blocks stood on edge two courses high. The eastern parapet, which is set back about 5m from the edge of the canal, is built of coursed dressed sandstone and sweeps around upstream either side of the river. Both arms of the eastern parapet have been partly rebuilt in concrete. Also on the upstream side of the aqueduct there is a weir which is built contiguously with the aqueduct. It consists of large sandstone blocks, carved to a round profile along the crest of the weir and is approximately 1.5m high. It was constructed to lower the bed of the river under the canal. The river runs beneath the canal through a single elliptical arch.