Thames, River

Ancient  Tamesis  or  Tamesa , also called (in Oxford, England)  River Isis  chief river of southern England. Rising in the Cotswold Hills, its basin covers an area of approximately 5,500 square miles (14,250 square km). The traditional source at Thames Head, which is dry for much of the year, is marked by a stone in a field 356 feet (108.5 metres) above sea level and 3 miles (5 km) southwest of the town of Cirencester. Some think a tributary, the River Churn, has a better claim to