Tay, a river of Scotland, draining nearly the whole of Perthshire, and pouring into the German Ocean a greater bulk of water than any other British river, rises on Benloy, on the Argyllshire border, at an altitude of 2980 feet. Thence it winds 118 miles ENE., SSE., and E. - for the last 25 miles as a tidal estuary, 1/2 mile to 3 1/4 miles broad, which separates Perth and Forfar shires from Fife. In the first 25 miles of its course it bears the names of Fillan and Dochart; it then traverses Loch Tay, and it afterwards passes Aberfeldy, Dunkeld, Stanley, Perth, Dundee, and Broughty-Ferry. Its principal affluents are the Tummel (58 miles long, and sometimes regarded as a northern head-stream), Isla, Almond, and Earn. The Tay, as it is the most beautiful of Scottish rivers, so it is unrivalled for its salmon-fisheries, whose rental in good years exceeds £20,000. Vessels of 100 tons can ascend as high as Perth, but even to Dundee the navigation of the firth is much impeded by shifting sandbanks. For the Tay Bridge, see Dundee.

Loch Tay lies 355 feet above sea-level, extends 14 1/2 miles NE. from Killin to Kenmore, is ½ to 1½ mile broad, 15 to 85 fathoms deep, and covers 6550 acres. It is a magnificent Highland lake, flanked on the north-west by Ben Lawers (4004 feet), and containing near its foot a wooded islet, with a fragment of an Augustinian priory, founded in 1122 by Alexander I., who here buried his queen, Sibylla. In Sept. 1842 Queen Victoria was rowed up Loch Tay, on which a steamer was launched in 1883, and a railway to which, at Killin, was opened in 1886. See the articles Ran-noch, Earn, Perthshire, etc, and J. Geddie's finely illustrated monograph on the Tay (1891).