aqueduct, but also as the location for the Lee Valley Reservoir Chain, stretching from Enfield through Tottenham and Walthamstow. A second significant corridor of canal, railways and industries was associated with the Brent, stretching from the Thames at Brentford, through Isleworth, Greenford, Alperton and Park Royal. The Colne (the historic boundary between Middlesex and Buckinghamshire) forms much of the western boundary of the county of Greater London. Right-bank tributaries Significant tributaries include the Mole, Wandle, Ravensbourne (tidal reach known as 'Deptford Creek') with its tributary the Quaggy, and the Darent and its tributary the Cray which together form part of the eastern boundary of Greater London. Smaller, some mainly subterranean tributaries include the Hogsmill River, Beverley Brook, Neckinger and Effra. The Wandle formed south London's nearest equivalent to the Lea Valley, with an industrial corridor stretching from the Thames at Wandsworth through Merton and Mitcham to Beddington and Croydon. A smaller corridor followed the Ravensbourne from the Thames at Deptford Creek through Lewisham, and many of the smaller rivers also once had mills. Canals A number of canals or canalised rivers have been constructed in the London area, mostly in the late 18th and early 19th centuries. These were originally for goods traffic, which has largely ceased. Within London the canals carried coal from the docks to many canal-side gas works and power stations (for example Brimsdown), and timber to timber yards, furniture manufacturers etc. (for example in Edmonton). Although most of the canals still survive today, they are used primarily for leisure craft. North of the Thames Canal construction in the London area started with navigation works on the Lea and Stort from 1424 onwards, leading to the River Lee Navigation and Bow Back Rivers. Initially used for transport of agricultural product from Hertfordshire, this later became an important industrial waterway connecting the heavily industrialised Lea Valley with the docks. A short-cut to the Thames avoiding the winding mouth of the Lea (Bow Creek) and closer to central London was provided by the Limehouse Cut (1760). A connection from London to the Midlands had been provided by the Oxford Canal since 1790, but this required navigation up the winding the upper Thames to Oxford. The completion of the Grand Junction Canal (later Grand Union) from the Thames at Brentford (1798 onwards) provided a more convenient route. In 1801 an arm was opened from the Grand Junction at Hayes to