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-ceal, 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 [. P 
