Geological Origin of the Present Scenery of Scotland 5 



Such, in baldest outline, is the general grouping of the rocks of 

 the country. From their original horizontal or gently inclined 

 position, the strata have been bent, broken, hardened, and for 

 thousands of square miles together, corrugated and contorted. 

 They have been cracked and displaced so generally, that probably 

 not a single square mile is free from some such " fault" or displace- 

 ment. And, lastly, they have, in many places, been traversed by 

 masses of melted rock, which either reached the antient surface 

 and flowed out as lava, or cooled and solidified under ground. 



But if we admit that the rocks have been so twisted and frac- 

 tured, it may seem, perhaps, that there ought to be no great 

 difficulty in assigning a cause to the present external contour of 

 the country. That contour, it may be asserted, must be due to 

 the inequalities produced by the subterranean movements which 

 folded and dislocated the rocks. This is, doubtless, a natural 

 inference, and it is at this moment still the current belief upon the 

 subject. But what seems the shortest and easiest explanation, is 

 not always the true one. And that this is the case in the present 

 instance, it is my object now to try to shew. 



In order as far as may be to gain clearness, I shall arrange my 

 argument under four propositions. 



/. — The hills and high grounds consist for the most part of hard 

 rocks ; the broad valleys lie for the most part on soft rocks. 



The simplicity of this proposition is apt to conceal its full 

 significance. Yet, if well weighed, it will be found to deal a heavy 

 blow to the interpretation which ascribes our present scenery to 

 the direct influence of subterranean movements. As illustrations 

 of its truth, reference may be made to the characteristic hardness 

 and toughness of the rocks of the Highlands, considered as a 

 whole, and to the uniformity of texture that runs through the hard 

 compact strata of the southern uplands. But nowhere is it more 

 strikingly exemplified than throughout the wide midland valley. 

 The prevailing rocks of that district are sandstones, and other 

 comparatively unresisting stratified deposits. But among these 

 there occur masses of very hard trap-rocks. Now, it is a familiar 

 fact, that while the low grounds lie upon the soft stratified rocks, 

 the crags and hills, almost without exception, are chiefly or wholly 

 formed of the hard trap. So invariably is this the case, that a 

 geologist who ascends some prominent hill, can, if he chooses. 



