Great Valley of the Scottish Lowlands. 113 



which it was prospectively adapted to the future necessities of 

 the human race, which was not to be called into existence until 

 after the lapse of a long succession of geological epochs. 



The Pentland, Campsie, and Ochill Hills, as well as many 

 others that occur within the limits specified, afford numerous and 

 striking examples of the effects produced by their intrusion 

 among the carboniferous strata, which, indeed, are no where 

 better seen than in the Plutonic group that surrounds Edin- 

 burgh. 



The Pentland range, which lies in a direction from south-west 

 to north-east, is prolonged to the shores of the Frith of Forth 

 by the trap-hills of Edinburgh, separating the coal deposits of 

 East and Mid-Lothian from those which are situated to the west- 

 ward of that chain, and form the great coal district in the basin 

 of the Clyde. These hills bear strong internal evidence of their 

 having been elevated at periods subsequent to the consolidation 

 of the carboniferous series. In the midst of the Pentlands, a 

 mass of sandstone has been thrown up, which forms a hill of con- 

 siderable elevation ; and, although grauwacke-slate, and portions 

 of a conglomerate of the same age, are seen at Habbie's-How, en- 

 veloped in the porphyry, it is highly probable that, if many of 

 the rocks of this range, which have hitherto been referred to the 

 transition period, were subjected to chemical analysis, they would 

 be found to consist of the sandstones or the slate-clay of the coal- 

 formation, altered to their present appearance by the effect of the 

 igneous rocks with which they are in contact. 



The occurrence of glance-coal, both in veins and disseminat- 

 ed in the porphyry and trap tuffa of the Calton Hill, and, in a 

 similar manner, in most of the other hills of this group, tends also 

 very strongly to confirm this opinion ; for it has most probably 

 been caused by the igneous matter having burst through the 

 coal strata in a fluid state, carrying up fragments of the coal with 

 it, which, being by this process deprived of their bituminous 

 qualities, have been converted into anthracite. 



VOL. XIII. part i. r 



