Firth locally the change is held to be at the Tail of the Bank where the river crosses a sandbar off Greenock at the junction to the Gare Loch, or even further west at Gourock point. However, some firths are exceptions. The Cromarty Firth on the east coast of Scotland, for example, resembles a large loch with only a relatively small outlet to the sea and the Solway Firth and the Moray Firth are more like extremely large bays. The Pentland Firth is a strait rather than a bay or an inlet. These are connected to, or form part of, the
Pentland Firth referring to the sea lanes of the entire west coast of Scotland down to Kintyre. One version of the 9th-century "Historia Brittonum" states that "the Britons originally filled the whole island with their peoples from the English Channel to the Sea of Orcs". On the Caithness (southern) side the Firth extends from Dunnet Head in the west to Duncansby Head in the east, while on the Orkney (northern) side from Tor Ness on Hoy in the west to Old Head on South Ronaldsay in the east. In the middle of the Firth are two significant islands, Stroma and Swona. The