Dispersed over all parts of the western Highlands, they are most numerous in the north-west, especially in the Outer Hebrides and in the west of the shires of Ross and Cromarty and Sutherland, where the surface of the Archean gneiss is so thickly sprinkled with them that many tracts consist nearly as much of water as of land.
In the basin of the gorges Moray Firth some fine examples may be seen on the Nairn and Findhorn, while on the west side of the Cromarty Firth some of the small streams descending from the high grounds of the east of the shire of Ross and Cromarty have cut out defiles in the Conglomerates, remarkable for their depth and narrowness.
The rocks overlying them to the east of the line of disturbance in the shires of Sutherland and Ross and Cromarty are fine flaggy schists.
To this were added from time to time the various estates scattered throughout Ross-shire - the most considerable of which were the districts around Ullapool and Little Loch Broom on the Atlantic coast, the area in which Ben Wyvis is situated, and a tract to the north of Loch Fannich - which had been acquired by the ancestors of Sir George Mackenzie (1630-1714), afterwards Viscount Tarbat (1685) and 1st earl of Cromarty (1703).
Desirous of combining these sporadic properties into one shire, Viscount Tarbat was enabled to procure their annexation to his sheriffdom of Cromarty in 1685 and 1698, the area of the enlarged county amounting to nearly 370 sq.
Would be required, and in 1912 it was proposed to construct defences both at Cromarty and at Scapa Flow.
It is a diamond-shaped peninsula jutting out from the mainland in a north-easterly direction, the longer axis, from Muir of Ord station to the South Sutor at the entrance to Cromarty Firth, measuring 20 m., and the shorter, from Ferryton Point to Craigton Point, due north and south, 12 m., and it has a coastline of 52 m.
It is situated near the head of Cromarty Firth where the valley of the Peffery unites with the alluvial lands at the mouth of the Conon, 182 m.
Scapa Flow was preferred to the Cromarty Firth as his chief naval base by Admiral Jellicoe, but no preparations had been made and everything had to be improvised, guns being landed from the ships to strengthen the defences.
Antiquarian remains are somewhat numerous, such as forts and cairns in Cromarty parish, and stone circles in Urquhart and Logie Wester and Knockbain parishes, the latter also containing a hut circle and rock fortress.