The Outer Hebrides being almost entirely composed of gneiss the epithet suitably serves them, but, strictly speaking, only the more northerly of the Inner Hebrides may be distinguished as Trap Islands.
C. Mackenzie, History of the Outer Hebrides (1903).
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.
Smith's Lewisiana, or Life in the Outer Hebrides (1874); Alexander Smith, A Summer in Skye (1865); Robert Buchanan, The IJebrid Isles (1883); C. F.
The chief islands of the Outer Hebrides are Lewis-with-Harris (or Long Island), North Uist, Benbecula, South Uist, Barra, the Shiants, St Kilda and the Flannan Isles, or Seven Hunters, an uninhabited group, about 20 M.
They have been broadly classified into the Outer Hebrides and the Inner Hebrides, the Minch and Little Minch dividing the one group from the other.
On Barra Head, the highest point of Berneray, and also the most southerly point of the outer Hebrides chain, is a lighthouse 680 ft.