Dumbarton, a royal, parliamentary, and municipal burgh and seaport of Scotland, chief town of Dumbartonshire, situated on the left bank of the Leven, near its junction with the Clyde, 13 m. N. W. of Glasgow; pop. in 1871, 11,414. It consists of one long semicircular street, and smaller streets and alleys diverging from it. On the opposite bank of the river is the suburb of West Bridgend, connected with it by a stone bridge. The principal business is ship building, both in wood and iron, there being five large yards employing over 3,000 men. A marine engine factory employs 400 men, and there are also two founderies, a forge, glass and bleaching works, a manufactory of patent windlasses, and a brewery. - Dumbarton is supposed to have been the Roman station Theodosia. At the confluence of the Leven with the Clyde, a mile below the town, is Dumbarton castle, famous in Scottish history, on an isolated precipitous rock upward of 500 ft. high and about a mile in circumference at the base. It is known to have been a stronghold 1,000 years ago, and it has sustained many sieges.