<P> In December 1761 Brindley undertook a survey of the route at Runcorn . His initial plan was to make the terminus at Hempstones, east of Runcorn Gap, but following a study of the tides and depth of water there, he decided instead to build the terminus west of Runcorn Gap . This change was designed to accommodate Mersey flats, although the low fixed bridges required that traffic on the canal be able to lower or unship their masts . Runcorn basin was almost 90 feet (27 m) above the Mersey, so a flight of ten locks, described as "the wonder of their time", was built to connect the two . Nine locks had a fall of 2 metres (7 ft), with a fall at the river lock of more than 6 metres (20 ft) at low water . It allowed vessels to enter and leave the canal on any tide . The connection to the Mersey was made on 1 January 1773 . The river's tidal action tended to deposit silt around the lower entrance to the locks, so to counteract this a channel, equipped with gates at each end and known as the Duke's Gut, was cut through the marshes upriver from the locks . At high tide the gates were closed, and with the ebb of the tide were opened to release water, which scoured the silt from the entrance to the locks . The cut created an island, known as Runcorn Island, crossed by Castle Bridge . </P> <P> The connection to Manchester was delayed by Sir Richard Brooke of Norton Priory . Concerned that boatmen might poach his game and wildfowl, Brooke did not want the canal to pass through his land . The Act included several stipulations: the canal should not come within 325 metres (1,066 ft) of his house; the towpath should be on the south side of the canal, furthest away from Brooke's house; there should be no quays, buildings, hedges or fences to obstruct the view; no vessels were to be moored within 1,000 metres (3,281 ft) of the house, other than during construction . Eventually, though, a compromise was reached . This included the construction of a link to the Trent and Mersey Canal at Preston Brook (permitted by the Trent and Mersey Canal Act of 1766), and the building of the canal's terminus to the west of Runcorn Gap . The Trent and Mersey link gave the Duke access to the Midlands, and forestalled the Weaver Trustees from making their own junction with the canal . The new extension also met with opposition from the Mersey and Irwell Navigation, until the duke purchased a controlling interest in the company . The first part of the new extension was opened in 1767, and completed in full by March 1776, but Brindley did not live to see its completion; it was continued by his brother - in - law, Hugh Henshall . </P> <P> The total cost of the canal, from Worsley to Manchester and from Longford Bridge to the Mersey at Runcorn, was £ 220,000 . Alongside the Mersey, the duke built Runcorn Dock, several warehouses, and Bridgewater House, a temporary home from which he could supervise operations at the Runcorn end . Two locks up from the tideway was a small dry dock . </P> <P> In 1766 the Duke gained a fourth act of parliament for a branch canal between Sale Moor and Stockport which was to follow the valley of the Mersey . The Act was applied for to counter a proposed canal that would give the towns of Stockport and Macclesfield access to the Mersey, via the River Weaver . The work was not done, the Act lapsed and this section of canal was never built . </P>

Where does the bridgewater canal start and end