THURSO (THE), a river of Caithness-shire. It rises among the mountains in the south-west corner of Halkirk, near the boundary with Sutherlandshire; and flows 12½ miles north-eastward, and 14 northward to the head of its cognominal bay, at the town of Thurso. Its course first bisects Halkirk; next for 1½ mile divides that parish from Thurso; and finally cuts the latter parish into two not very unequal parts. Its tributaries are neither numerous nor large; and its greatest breadth is about 300 feet. Its banks are almost everywhere destitute of wood; but, in other respects, are, in many places, softly beautiful.