STAFFA, a small uninhabited basaltic island on the western side of Scotland, about 8 miles W. from Mull, in 56° 28' N. let., 6° 20' W. long.
The island is composed of amorphous and pillared basalt: the pillars have in many parts of the rugged coast yielded to the action of the sea, and permitted the formation of caves, some of them uncom monly picturesque, which are generally arched over by what seems to be amorphous trap-rock, but really is often prismatised in an irregular manner. The island has a very broken and unequal surface, affording poor pasture.
Skirting the coast in a boat, the caves and ranges of pillars, erect, or curved beneath a huge entablature of rock, and the regular pave ment formed by the augular sections of the pillars, astonish the spectator. Fingal's Cave, the largest and most attractive of the caves, may bo entered on foot on the south side, along a rugged pavement of pillar-tops. Its roof is formed partly of pillar-sections, and partly of the already-mentioned amorphous trap ; the sides are straight ver tical prisms of basalt, washed at their base by a deep and often tumul tuous sea. Its length from the rock outside is 371 feet, from the pitch of the arch 250 feet ; the breadth at the mouth is 54 feet, at the farther end 20 feet ; the height of the arch at the mouth is 118 feet, at the inner end 70 feet ; the pillars outside vary from 40 to 55 feet in height. The Boat Cave, the Cormorant Cave, and Fingal's Cave,
may, in ordinary weather, be explored in a boat, and a landing may be effected on Buachaill6 (Boo-cha-la), the 'Herdsman's Isle,' which is remarkable for its arched columns of basalt.
The basaltic mass of Staffa may he regarded in three parts : a sub jacent amorphous and lava-like mass, 11, 17, or 20 feet exposed, on which (especially beyond the north-west side of Fingal's Cave) the pillars rest, and these are covered by a seemingly amorphous but really irregularly prismatic entablature, from 30 to 66 feet in thick ness. The tops of the pillars are usually in a nearly regular plane declining to the south-east, and their bases are also iu a surface nearly parallel. The section of the pillars is rarely triangular or quadrangu lar, generally pentagoual or hexagonal. Some of them are two feet in diameter, others as small as one foot, nine inches, or even six inches. They are less regularly jointed than those of the Giants' Causeway, and usually the joint surfaces are concave in the lower stone. Zeolitic minerals occur sparingly in the basalt and in the interstices of the pillars. Steamers make excursions from Oban to Staffs during summer.