Geological Origin of the Present Scenery of Scotland. 1 3 



voluted and highly incUned strata has been planed down into a 

 long table-land. The arches have been so smoothly cut away as 

 to give no indication of their existence by any rise in the outline 

 of the ground. We walk over the edges of the rocks for miles, 

 and, so far as the surface of the ground indicates, we might suppose 

 ourselves to be upon a series of horizontal or gently inclined strata. 

 It is along some of the striking coast sections that these features 

 are most convincingly brought before the observer. The range of 

 precipice to the north-west of St Abb's Head, for example, shews 

 a series of highly-tilted strata, often indeed placed on end. (Fig. 

 4.) There, in a distance of five or six miles, sixteen or eighteen 

 distinct arches and troughs of the strata can be counted. Now, it 

 is plain that but for denudation there would have been along this 

 coast some eight or nine huge conical or dome-shaped mountains, 

 separated from each other by v-shaped depressions of correspond- 

 ing magnitude. But what do we find instead? The rocks are 

 planed off along the top of the cliff, and all traces of arches or 

 troughs is effaced from the contour of the surface. 



Again, throughout the midland valley, on every side we meet 

 with monuments of denudation. Every hill of trap in that wide 

 region, is a memorial of the destruction of softer rocks that once 

 surrounded and overlaid it. The trap stands out in relief, because 

 it is harder, and has thus been more able to resist the force ot 

 abrasion which has wrought such havoc among the less obdurate 

 stratified masses. It can be demonstrated, that these trap-hills 

 were once buried under several thousand feet of sandstone, shale, 

 limestone, coal, and other strata, and this deep overlying mass 

 has been, as it were, peeled off from districts of many hundreds 

 of square miles in extent (see view of Lomonds, &c., page 6). 



So much for the general denudation of the country. Let me, 

 however, point for a moment to one or two examples of the pro- 

 cess, as developed in the history of a single hill or mountain. 



Along the north-western sea-board of the Highlands, there rises 

 a chain of lofty and more or less isolated mountains of singularly 

 pyramidal form, and a somewhat sombre red tint, barred along 

 their sides with nearly horizontal lines and ledges, which look like 

 huge courses of masonry, and scarred with deep clefts and rifts, 

 where often the winter snow lingers far into the summer. These 

 striking eminences are formed of that red Cambrian sandstone 

 already referred to {b, in fig. i), and their horizontal bars mark 

 the edges of the flat strata. They are, in fact, built up of hori- 



