1884-85.] Edinburgh Naturalists Field Club. 237 



immense thickness of Carboniferous rocks was bent into anticlines 

 and synclines, and broken and faulted, and a long section of the 

 district now occupied by the north-eastern portion of the Pentland 

 Hills pushed up to a height of 2000 or 3000 feet. This is 

 proved by the two great faults that run parallel with the hills 

 at their north-eastern portion. That enormous denudation again 

 took place is abundantly proved by the shorn-off and levelled-up 

 condition of anticlines, synclines, and faults. The long stony 

 ridge that had been upheaved was denuded of its superimposed 

 sedimentary strata, and the buried volcanic rocks again exposed 

 to the action of the waves, carving gleos and valleys through 

 the ridge, and leaving the harder portions standing up as hills : 

 and so in the middle and south-western portions of these hills the 

 same denudation had been going on, for what must have been a 

 great platform of nearly horizontal beds of sandstone has now got 

 valleys scooped out of it in every direction, some of them nearly a 

 thousand feet deep. That the ice of the glacial period had a great 

 hand in finally moulding these hills and the adjacent country into 

 their present form, there can be no doubt. Evidence of ice-action 

 is common all over this range of hills. Eubbings and scratchings 

 produced by ice — or rather the hard materials fixed in the ice 

 — are found high up on the hill-sides, and in one instance, at 

 least, on the top of one of the highest hills ; boulders, some 

 of them ten and twelve tons in weight, from far-off distances, 

 strew the hill-sides ; while boulder-clays lie packed in the val- 

 leys, in many places containing materials foreign to the district. 

 All these tell of a time when this country was under severe arctic 

 conditions — when a great ice-sheet swept with slow but irresistible 

 force over the face of the country, rubbing and grinding down the 

 rocks, packing the eroded materials into the hollows, and form- 

 ing what is known as boulder-clay and other glacial deposits. Nor 

 has nature been idle among these hills since the glacial period, 

 for frost, rain, and wind have been busy on their sides and in the 

 valleys, breaking up and carrying away to lower levels the mate- 

 rials of which the hills are composed, as the deep ruts and glens 

 formed by the burns that run from their sides testify. 



Such is a brief, and, I feel, very imperfect sketch of one of the 

 most interesting districts in Scotland, and you will readily see that 

 to do anything like justice to sucli a subject would take much 

 moi'e time than the nature of our meetings will allow. However, 

 I hope that the few remarks I have made may induce other mem- 

 bers of the Club to take hammer in hand, and go and investigate 

 for themselves. 



