65 



as already remarked, in crossing the country from north-east to 

 south-west. To this succeed the gneiss tracts, which, as we advance 

 north-west, keep with us till we reach the granite axis of the Gram- 

 pians. Along this axis, however, it is now known that the granite does 

 not form an unbroken continuous ridge or line of heights. It occurs 

 rather in independent elliptic shaped masses, its place on the axis 

 being often taken by mountains of gneiss, porphyry, or quartz rock. 



Such, then, is the singular abnormal position of the Arran granite, 

 which gives to this island all its peculiarities, both as regards its 

 geographical features and its geological structure. The protrusion 

 of so large a body of igneous rock by plutonic fires along the line of 

 junction of the older slates and the secondary formations, and its ele- 

 vation to a great height in a space so limited, might naturally be 

 expected to produce phenomena of varied interest, such as have been 

 alluded to in the opening paragraph of this section. 



45. 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 penetrating and dividing them, 

 consist entirely of this rock. It is remarkable, however, that at no 

 point does the granite reach the sea coast. In its elevation from the 

 plutonic depths, it bore up with it a narrow band or framework of 

 clay slate, of the second or dark coloured variety, which completely 

 encircles the nucleus. The structure of this portion of the island is 

 shown in the cut annexed, representing an ideal east and west section 



(a) Coarse grained granite ; (&) fine grained granite ; (c) slate; (d) old red sand- 

 stone ; (e) carboniferous strata. 



from Corrie to White-Farland. From the mouth of the lorsa water 

 at Dugarry, round the west side of the island by Imochair, Thunder- 

 gay, and Catacol, to Loch Kanza, this slate 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 preci- 

 pitous 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 



K 



