<Tr> <Th> Length </Th> <Td> 188 km (117 mi) </Td> </Tr> <Tr> <Th> Basin </Th> <Td> 4,970 km (1,919 sq mi) </Td> </Tr> <P> The River Tay (Scottish Gaelic: Tatha) is the longest river in Scotland and the seventh - longest in the United Kingdom . The Tay originates in western Scotland on the slopes of Ben Lui (Scottish Gaelic: Beinn Laoigh), then flows easterly across the Highlands, through Loch Dochart, Loch Iubhair and Loch Tay, then continues east through Strathtay (see Strath), in the centre of Scotland, then southeasterly through Perth, where it becomes tidal, to its mouth at the Firth of Tay, south of Dundee . It is the largest river in the UK by measured discharge . Its catchment is approximately 2,000 square miles (5,200 km), the Tweed's is 1,500 square miles (3,900 km) and the Spey's is 1,097 square miles (2,840 km). </P> <P> In the 19th century the Tay Rail Bridge was built across the firth at Dundee as part of the East Coast Main Line, which linked Aberdeen in the north with Edinburgh and London to the south . The bridge, designed by Sir Thomas Bouch, officially opened in May 1878 . On 28 December 1879 the bridge collapsed as a train passed over . The entire train fell into the firth, with the loss of 75 passengers and train crew . The event was commemorated in a poem, The Tay Bridge Disaster (1880), written by William McGonagall, a notoriously unskilled Scottish poet . The critical response to his article was enhanced as he had previously written two poems celebrating the strength and certain immortality of the Tay Bridge . A second much more well received poem was published in the same year by the German writer Theodor Fontane . A.J. Cronin's first novel, Hatter's Castle (1931), includes a scene involving the Tay Bridge Disaster, and the 1942 filmed version of the book recreates the bridge's catastrophic collapse . </P>

Where does the river tay start and end
find me the text answering this question