k.^^'2 



Geological Origin of the Present Sce)iery of Scotland 3 



that the prhiciplcs applicable to the history of the 

 shaping of the Scottish hills and valleys are of 

 wider significance, and that what is true of Scot- 

 land is, with the necessary local modifications, true 

 also of other countries. 



First of all, let us lay aside the vague popular 

 belief that all mountains are directly due to great 

 upheavals, and all valleys to depressions or rents 

 of the earth's surface. Without lingering at pre- 

 sent to enquire whether or how far this belief 

 is founded on reality, let us proceed to note the 

 simpler elements of the geological structure of the 

 country. For it is evident that we must know 

 something of the varying nature and arrangement 

 of the rocks before we can place ourselves in a 

 position to understand how the hills and valleys 

 have been formed out of them. 



The accompanying section represents in a gene- 

 ralized form the main geological features of the 

 country. It shews the existence of three great 

 divisions, each characterized by a distinct group 

 of rocks, and, consequently, as we shall afterwards 

 see, by a distinct type of scenery. These divisions 

 are, u/, the Highlands, ranging from the extreme 

 north-west to the lowland border that stretches 

 from the Clyde to the coast of Kincardine; zd, 

 the Southern Uplands, extending from sea to sea, 

 between a line drawn from St Abb's Head to Gir- 

 van, and another more sinuous line from the 

 Solway to near Berwick-on-Tweed ; and 3^, the 

 Midland Valley — a low, broad, undulating, and 

 often hilly tract, lying between the other two dis- 

 tricts, and embracing the Firths of Tay, Forth, and 

 Clyde. 



Beginning at the north-west end of the section, 

 we find rising from the Atlantic sea-board, a group 

 of hard, gnarled, crystalline rocks ia)^ to which the 

 name of Laurentian is now applied. They are 

 overlaid with a thick mass of dull red sandstone 

 {h), called Cambrian, which rises into those won- 

 derfully picturesque mountains stretching from 



(3 bi) 



