284 Physical Structure and 



form about nine-tenths of the Highlands of Scotland 

 north of the Grampians. They consist chiefly of gneiss 

 and mica-schist, with numerous bosses of granite, and 

 near their base are partly formed of thick masses of 

 quartz-rock, interbedded with two bands of crystalline 

 or semi-crystalline limestone, containing Lower Silurian 

 fossils, by which their age has been ascertained. 



Next, on the north-east coast, we have the Old 

 Eed Sandstone, the Upper Silurian rocks, which form 

 such an important part of the English strata, being 

 absent. 1 



Farther south, above the Old Ked Sandstone, lie 

 the Carboniferous rocks, consisting of Calciferous sand- 

 stone, limestone, and Coal-measures, the limestone 

 forming in Scotland but a very small intercalated part 

 of the series. These strata lie in the great valley be- 

 tween the Old Eed Sandstone of the Ochil range on the 

 north, and the Old Eed and Silurian rocks of the Lam- 

 mermuir, Moorfoot, and Carrick hills, on the south. 

 Besides these formations, there are others in some of 

 the Western Islands, such as Skye and Mull, and in 

 the east and south of Scotland, and elsewhere. These 

 consist of various members of the Lias, Oolitic, and 

 Miocene strata in the Isles, and a little Permian in 

 the south, which, however, form such a small part of 

 Scotland, that only in the Isles and a small part of the 

 mainland at Ardnamurchan, and on the hills that over- 

 look the Sound of Mull, do the Miocene igneous rocks 

 seriously affect its physical geography. Therefore I 

 shall chiefly confine myself to the mainland of the 

 north Highlands, for I wish specially to treat of the 



1 This order for the north of Scotland was first established by 

 Sir K. Murchison. See ' Siluria.' 



