Geography of Kent and Dungeness have been formed by accumulation of alluvium. Kent's principal river, the River Medway, rises near Edenbridge and flows some 25 miles (40 km) eastwards to a point near Maidstone, when it turns north. Here it breaks through the North Downs at Rochester before joining the River Thames as its final tributary near Sheerness. The river is tidal as far as Allington lock, but in earlier times cargo-carrying vessels reached as far upstream as Tonbridge. The Medway has captured the head waters of other rivers such as the River Darent. There are other rivers in Kent, most notably the
Borough of Maidstone earliest in the county – that to Rochester and Chatham – was opened in 1728. In modern times, two motorways – the M2 and the M20 – pass to the far north of the borough and just north of the town centre of Maidstone respectively. The earliest line through Kent was built by the South Eastern Railway. It was not, however, built to pass through Maidstone: instead, a station was built at Paddock Wood railway station, then named "Maidstone Road", some six miles away. It was only in the period between 1844 (when that main line was connected by a