Geology of Kent to uplift, sedimentation, and marine erosion. The Isle of Thanet was till recently (AD 960) an island, formed around a deposit of chalk. The channels silted up with alluvium. Similarly Romney Marsh 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
Borough of Maidstone for cargo-carrying craft as far upstream as Tonbridge, and it was only in the 19th century that the railways brought any change. More recently, various works have been carried out to control the frequent flooding in the clay vale upstream of Maidstone. Maidstone, as its importance warranted, has been the hub of roads for many centuries. It lies very close to the Pilgrims' Way; and two Roman roads met south of the town: one from Rochester to Hastings the other branching off to the East Kent coast and Dover. In the 18th century came the turnpiked roads. One of the