TAY, The, the longest river in Scotland, has its source on the northern side of Ben Lui, on the borders of Argyllshire and Perthshire, being known in its earlier course as the Fillan, and, after forming Loch Dochart, as the Dochart, until entering Loch Tay, 25 miles from its source, at an elevation above sea-level of 553 feet. Its course through Perthshire is described in the article on that county. Its total length to the town of Perth is about 95 miles, and it drains a total area of about 2400 square miles, while its estuary extends for about other 25 miles. The navigation of the estuary is somewhat impeded by sandbanks. The only important port is Dundee, but vessels of 100 tons can pass up to Perth, the river being tidal to 2 miles above it. The salmon fisheries on the river and its estuary are among the most valuable in Scotland. A railway bridge over the Tay at Dundee, designed by Sir Thomas Bouch (see Bridges, vol. iv, p. 340), was opened for traffic 31st May 1878, but was blown down during the crossing of a passenger train 28th December 1879. Some distance to the west a new bridge, designed by W. H. Barlow, was commenced in 1882, and was opened for general traffic 20th June 1887.