CHAP. XXXVIII 
RIVERS OF THE PERIOD 
: 35 
that the ridge of the Scuir corresponds with the area occupied by a mass of 
pitchstone, and that while the basaltic rocks cover the whole of the rest of 
the southern half of the island, they gradually rise towards the north, 
Fig. 276. — Geological Map of tlie Island of Eigg. 
P, Pitclistone-lava of the Scuir ; R, old river gravel under pitchstone ; p p, small veins of Pitchstone ; b 6, dykes, 
veins and sheets of intrusive basalt ; the short black lines running north-west and south-east are basalt dykes ; 
f f, granophyre sills ; D, bedded basalts with occasional tuffs ; F, andesite ; 1, 2, 3, 4, clays, shales, sandstones, 
limestones, etc. (Jurassic); xx, Loch Beinn Tighe ; x, Loch a Bhealaieh. General dip of the rocks. 
successive members of the Jurassic series making their appearance until, at 
the cliffs of Dunan Thalasgair, the latter cover the greater part of the 
surface, and leave the volcanic rocks as a mere stripe capping the cliffs. 
In the section (Fig. 277) the general structure of the island is represented. 
