Carboniferous Strata. 299 



by denudation. The reason of this is, that during fre- 

 quent oscillations of land, relatively to the level of the 

 sea, the higher ground was much more often above 

 water than the lower part, and therefore exposed to 

 waste and destruction. To understand this thoroughly, 

 let us suppose that the whole of the formations now 

 forming this area were, in an ancient epoch, underneath 

 the sea, and then let parts of it be raised, more or less 

 above that level, well into the air. Part of the area 

 now known as the Lammermuir Hills, then covered by 

 Old Red Sandstone and Coal-measures, rose above the 

 water, and was immediately subjected to the wear and 

 tear of breakers on the shore, and of rain, rivers, frost, 

 and other atmospheric influences ; while, on the other 

 hand, that portion that lay deep in the synclinal curve 

 was beneath the level of the sea, and thus escaped 

 denudation, because no wasting action takes place in 

 such situations. 



By geological accidents such as these, the greater 

 features of Scottish scenery have been produced. The 

 Highlands are mountainous because they are composed 

 of rocks much disturbed, metamorphosed, and mostly 

 crystalline, and intermingled with great and small 

 bosses of hard granite. All of these rocks having been 

 often and long above water, have been extremely de- 

 nuded : such denudations having commenced so long 

 ago, that they date from before the time of that ex- 

 tremely venerable formation, the Old Ked Sandstone, 

 probably indeed ever since what, for want of better words, 

 we term the close of the Lower Silurian epoch, and the 

 waste has been going on, more or less, down to the 

 present day. 



Being formed for the most part of materials of 

 great but unequal hardness, and associated with masses 



