LONG, LOCH, an arm of the sea on the W. coast of Scotland, stretching first N. then N.E. from the Firth of Clyde, and separating the counties of Argyll and Dumfries. It is 20 miles long by from 1 to 2 miles broad. From its centre a branch loch stretches for 4\frac{1}{2} miles northwards into Argyllshire, called Loch Goil. The shores of both lochs are mountainous and highly picturesque.