THE SLATES. 9 



The Slates. 



5. The granite nucleus occupies by far the greater portion 

 of the northern half of the island. The three mountain 

 groups already described, with the glens and valleys pene- 

 trating and dividing them, consist entirely of this rock. It 

 is remarkable, however, that at no point does the granite 

 reach the sea coast. It is everywhere enclosed by a narrow 

 band or framewoi'k of clay slate, of the second or dark 

 coloured variety, which completely encircles the nucleus 

 (see Map). The structure of the northern half of the island 

 is shewn in the preceding section (fig. 3), which crosses the 

 nucleus east and west from Corrie to White Farland. In this 

 section, a is coarse-granite ; b, fine granite ; c, slate ; d, old red 

 sandstone; e, sandstone with coal plants;/, limestone with 

 product!, corals, <fec. ; g, dikes of basalt and pitchstone. 



From the mouth of the lorsa Water at Dougrie, round 

 the west side of the island, by Imochar, ;Thundergay, 

 and Catacol, to Loch Ranza, the slate rock occupies 

 the coast, and forms a belt of considerable but varying 

 breadth. Its junction with the granite is seen in almost 

 every stream, and in many points along the western slopes 

 of the lower hills. It extends all round the precipitous 

 sides of the Loch Ranza valley, and to a short distance 

 east of Newton point, which forms the north-east angle of 

 the loch, as far as a small stream called Alt-Mhor. It here 

 retires from the shore, and forms the high northern ridge 

 already mentioned; the coast from this point eastwards, and 

 then southwards, being occupied partly by old red sandstone, 

 and partly by coal sandstones, beds of carboniferous lime- 

 stone and of coal and coal shale being interposed amid the 

 beds of the latter. The band of slate is of considerable 

 breadth in this northern ridge, but narrows very much on 

 approaching the opening of Glen Saunox ; along the hill-sides 

 southward, from the base of Cioch-na-h'oighe to the slopes 

 over Con-ie, the breadth vai'ies from 25 to 40 or 50 yards. 

 Farther south, as it sweeps round south-west between 



