The Thames is a river flowing through southern England, in its lower reaches flowing through London into the sea. It is one of the major waterways in England. Because the Thames is so well known, it is usually unnecessary to call it the River Thames. Indeed, Londoners often refer to it as 'the river', in expressions such as 'south of the river'. It is never correct to call it the Thames River.
At the height of the last ice age around 12000 years ago, Britain was connected to mainland Europe via a large expanse of land known as Doggerland. At this time, the Thames was much larger than it is today, with its source rising much further west in present-day Wales. The river's course continued out into Doggerland, where it met the Rhine. Thus the two rivers were at one time part of the same river system.
The Thames provided the major highway between London and Westminster in the 16th and 17th centuries. The clannish guild of watermen ferried Londoners from landing to landing and tolerated no outside interference.
In the 17th and 18th centuries, during the period now referred to as the Little Ice Age, the Thames often froze over in the winter. This led to the first Frost Fair in 1607, complete with a tent city set up on the river itself and offering a number of amusements, including ice bowling. After temperatures began to rise again, starting in 1814, the river has never frozen over completely. The building of a new London Bridge in 1825 may also have been a factor; the new bridge had fewer pillars than the old, so allowing the river to flow more freely, thus preventing it from flowing slowly enough to freeze in cold winters.
By the 18th century, the Thames was one of the world's busiest waterways, as London became the centre of the vast, mercantile British Empire. During this time, one of the worst river disasters in England took place on 3 September 1878, when the crowded pleasure boat Princess Alice collided with the Bywell Castle, killing over 640.
In the 'Great Stink' of 1858, pollution in the river reached such proportions that sittings at the House of Commons at Westminster had to be abandoned. A concerted effort to contain the city's sewage, by constructing massive sewers on the north and south river embankments followed, under the supervision of engineer Joseph Bazalgette.
The coming of rail and road transportation and the decline of the Empire, in the years following 1914, have reduced the prominence of the river. London itself is no longer a port of any note and the Port of London has moved downstream to Tilbury. In return, the river has undergone a massive clean-up, since the filthy days of the late 19th and early- to mid-20th centuries and aquatic life has returned to its formerly 'dead' waters.
In the early 1980s a massive flood-control device, the Thames Barrier, was opened. It is closed several times a year to prevent water damage to London's low-lying areas upstream (as in the 1928 Thames flood for example). In the late 1990s, the 12-km-long Jubilee River was built, which acts as a flood channel for the Thames around Maidenhead and Windsor.
The Thames, from Middle English Temese, is derived from the Celtic name for the river, Tamesas , recorded in Latin as Tamesis and underlying modern Welsh Tafwys "Thames". The name probably meant "dark" and can be compared to other cognates such as Irish teimheal and Welsh tywyll "darkness" and Middle Irish teimen "dark gray".