T. Mellard Reade — British Geology. 561 



lengthening beds, unable to expand, laterally folded upon themselves, 

 and the whole mass of sediment, by cubical expansion, increased in 

 volume to the extent shown, by the rise of the mountain mass above 

 the sea-level. But we are not to limit this action to the immediate 

 mountain area, for the flanking area, pi'obably largely constituted of 

 more horizontal beds, now covered by newer deposits by successive 

 lateral expansions, added to the folding and heaping up of the 

 mountain masses. 



Areas occupied by the Hocks newer than the Carboniferous. 



If this relation between extensive and massive sedimentation 

 and mountain-making stood alone it might justly be considered as 

 merely accidental. I have, however, elsewhere shown that such 

 relations may be traced in every known great mountain range ; that 

 formations here thinly developed and horizontal are in the Alps 

 and Pyrenees, to go no further afield, extensive, thickly developed, 

 and thrown into immense mountain masses. 



In Britain the Permian and Trias, which lie unconformably upon 

 the Carboniferous, reach a thickness of some 6U00 feet, but the 

 variation of thickness is very considerable from the overlapping of 

 these formations on the mountain slopes. They are, however, as 

 a rule, more affected by folding and faulting than the succeeding 

 formations, and constitute some considerable hills and escarpments. 



The Jurassic and Cretaceous occupy the largest part of the eastern 

 half of England, and may be put down at perhaps 5000 feet, and 

 the Tertiary at say 1500 feet ; the total thickness of the British 

 rocks from the Permian to the Tertiary inclusive, working out to 

 about 12,500 feet. It is, howevei*, very questionable whether such 

 an aggregate thickness occurs in any one locality ; while in the 

 case of the older rocks, from the base of the Permian down to the 

 base of the Cambi'ian they are developed in great thickness in direct 

 superposition. 



Characteristics of the Folding of the Eastern and Western Areas of 

 England and Wales contrasted. 



The rocks already described as occupying the eastern half and 

 south of England are characterized by long low folds breaking into 

 sharp anticlinals and synclinals at a few points onlj^ such as in 

 the Chalk at Flamborough Head and in the Tertiaries of the Isle 

 of Wight, the eroded edges of these long folds forming the 

 characteristic escarpments stretching across the country in a south- 

 westerly and north-easterly direction. Sharply contrasted with these 

 long undulations are the strata forming the mountain nuclei of 

 Wales and Cumberland, where we find the rocks sharply bent and 

 compressed, the remnants of the primitive folds forming by denuda- 

 tion the mountain scenery as now beheld by us. Intermediately we 

 find areas of the Carboniferous and Old Red having a horizontal 

 development, such as is to be seen in the Carboniferous of the 

 neighbourhood of Whernside and Ingleborough, and can be well 

 studied near to Dent, where the much contorted Silurians are in 



DECADE IV. — VOL. II. NO. XII. 36 



