Firth of Forth(redirected from Forth, Firth of)
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Firth of Forth
an estuary in the North Sea, in eastern Scotland. The Firth of Forth is about 80 km long and up to 46 m deep. Its width is about 25 km at the entrance and 2–5 km at its western end. The firth contains many shallows and reefs and is subject to semidiurnal tides, which reach a magnitude of more than 6 m. Edinburgh is the most important port on the estuary. A canal that cuts through the Clyde river connects the Firth of Forth with the Firth of Clyde.