bascule bridge

a kind of drawbridge this the only Scottish one is a single span or leaf which lifts 90 degrees by water counterweight to enable boats to travel on the White Cart Water  beneath the A8 near Renfrew.
Built in 1922 and restored 2005 it provided a 90 foot navigation channel to  Paisley Harbour and the large Babcock and other  works upstream and downstream to the confluence with the Clyde opposite John Brown Shipyards
Built by Sir William Arrol and Co Ltd born in nearby Houston in 1839 his firm also built Tower Bridge London a double leaf bascule and the Forth Rail Bridge