CLYDE, the most important river of Scotland, and the third in point of magnitude, has its origin from numerous small streams rising at a height of about 1400 feet above the level of the sea, in the mountains which separate Lanarkshire from the counties of Peebles and Dumfries. It flows first in a northerly direction, with a slight inclina-tion eastward as far as Biggar, where, in time of floods, a junction is sometimes established with the system of the Tweed by means of the Biggar Water. After uniting with the Douglas near Harperfield, it takes a north-west course, passing Lanark, Hamilton, and Glasgow, and merges in the Firth of Clyde below Dumbarton. From its source to Dumbarton it is about 73 miles in length, the direct district being about 52. Its principal tributaries are the Douglas, the Nethan, the Avon, and the Cart from the left, and the Medwyu, the Mouse, the Calder, the Kelvin, and the Leven from the right. Of the celebrated Falls of Clyde, three are above and one below Lanark ; the uppermost is Bon-nington Linn, the height of which is about 30 feet ; the second is Corra Linn, where the water dashes over the rock in three distinct leaps, and resumes its course at a level 84 feet lower. Dundaff Linn is a small fall of 10 feet; and at Stonebyres there are three successive falls, together measuring 76 feet in height. At high water the Clyde is navigable to Glasgow for the largest class of merchant vessels. See GLASGOW.