Overview
The River Thames, known alternatively in parts as the Isis, is a river that flows through southern England including London. At 215 miles, it is the longest river entirely in England and the second-longest in the United Kingdom.
Description
River Thames, 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 meters) 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 being the source; it rises near the village of Seven Springs (700 feet [213 meters] above sea level), just south of Cheltenham.