Geological Origin of the Present Scenery of Scotland 7 



rising into bold crags, or sweeping in far vistas eastward along 

 the edge of the Carse of Gowrie. In all these examples, he is 

 looking upon hard trappean rocks, which project boldly from the 

 softer sedimentary strata among which they lie. 



Thus, over the whole country, no matter what may be the varia- 

 tions in geological structure, wheresoever the observer notes some 

 more conspicuous mass of rock, he may, with tolerable certainty, 

 assume its greater prominence to be an accompaniment of superior 

 hardness. But how can this fact be explained by the common 

 hypothesis? If the present inequaHties of surface have been pro^ 

 duced by subterranean agencies, how is it that, as a rule, the up- 

 heaved masses should have been hard, and the depressed portions 

 soft ? Surely the varying texture of the rocks now at the surface 

 could have had no influence on the antient underground movements. 

 Is it not, on the contrary, evident that, whatever may have been 

 the original influence of these movements, the existing outlines of 

 the country must be in great measure dependent upon some cause 

 where the relative hardness or softness of the rocks comes into 

 play ? 



II. — The vwuntains and hills are not mere cnunplings or foldings 

 of the earth's crust, nor are they due to the form assumed by melted 

 rock when forced from beneath to the surface. 



This statement requires for its full comprehension a little more 

 geological knowledge than the last, but, with the aid of the 

 foregoing section, the reader will have no difficulty in follow- 

 ing the line of reasoning. On reference to fig. i. he will notice 

 that several of the mountains there sketched are formed of strata 

 which dip inwards both from the north-west and south-east. 

 Many Highland mountains exhibit this structure, one of the most 

 striking examples being Ben Lawers ( x in fig. i). That huge 

 hill consists of gnarled schists, which are grouped in the form of a 

 basin. They dip under the hill from Glen Lyon, and rise up again 

 on the other side above Loch Tay. Now, it is plain that, if the 

 broad foldings of the strata had given rise to the outlines of the 

 country, Ben Lawers, instead of being a mountain, ought to have 

 been a valley. Again, along the depression of Loch Tay the 

 strata arch over, as shewn in the section to the right of the asterisk. 

 Consequently, the fold at Loch Tay, instead of a valley, ought to 

 have given rise to a mountain. No structure is of more frequent 



