12 MONOGRAPH OF DURA DEN. 



The primary series, according to this tabular view, are by 

 far the most widely developed of the rock formations of the 

 earth. In Scotland they cover upwards of nineteen thousand 

 SQUARE MILES, or about two-thirds of its superficial extent. 

 They prevail chiefly in the Northern Highlands ; and, from 

 their upheaval by subterranean fires, give rise to all their 

 picturesque grandeur and diversified outline of mountain, 

 strath, loch, glen, and valley. The lower group of the second- 

 ary formation is, in part of the series, limited to the southern 

 division and border districts, and the central districts are 

 occupied wdth the old red sandstone, the coal metals, ironstone, 

 and limestone. 



The upper secondary and tertiary formations are in Scot- 

 land of very limited extent, and chiefly in small patches 

 confined to Dumfriesshire and the Hebrides. They consti- 

 tute the prevailing rocks over nearly two-thirds of England, 

 in all the eastern, southern, and midland counties. The 

 igneous class of rocks again, with the exception of the 

 granite, all lie within the area of the coal-field, or form its 

 outworks, constituting the Sidlaw, Ochil, Campsie, Kilpatrick, 

 and Pentland ranges of hills. The Grampians, and other lofty 

 mountains in Arran, Skye, Ross and Sutherland shires, are 

 composed of granite, gneiss, mica-schist, quartz, limestone and 

 clay-slate. 



Following the hue of Section, we shall briefly notice the 

 relations and mineral constituents of the successive formations, 

 in their order of superposition, from the Grampians to Dura 

 Den, including a space of about twenty miles in lineal extent. 



Granite constitutes the nucleus of the Grampian range 

 from shore to shore over Scotland. It is the lowest funda- 

 mental rock, having its seat deep in the crust of the earth ; 

 and it likewise forms the top of nearly all the Bens, the 

 loftiest mountains in the Highlands. The prevailing consti- 

 tuents are quartz, felspar, and mica. Where hornblende is 



