132 NEOZOIC TIME. [CHAP. VIII. 



similarly irregular coast-line. Both the eastern and western 

 land- tracts had long been exposed to the action of rain and 

 rivers, and were doubtless sculptured into a network of 

 ravines and valleys, which opened into wider valleys and 

 plains at lower levels. That one such valley opened east- 

 ward along the site of the British Channel is evident from 

 the manner in which the Keuper marls trend westward 

 into that channel ; this old valley in and south of Glamor- 

 ganshire lay probably along the course of the Carboniferous 

 Limestone, and led westward into the heart of the hilly 

 region which then united Pembroke and Devonshire, and 

 of which Lundy Island is the sole remaining fragment. 

 Another smaller inlet, penetrating into the centre of Devon- 

 shire, seems to be indicated by the strip of Trias which ex- 

 tends westward from Crediton, and doubtless there were 

 many other such inlets, bays, and estuaries, along the 

 shores of the great Triassic lake. 



Such was the lake in which the sandstones, marls, salt 

 and gypsum beds of the Upper Trias were deposited. The 

 climate of the country was probably warm and dry, and 

 the saline waters of the lake were doubtless clear, and 

 probably of that deep blue tint which such waters generally 

 present. The ripple-marks, sun-cracks, and reptile-tracks 

 so frequent on the surface of the sandstones, show that 

 the volume of the lake- waters was subject to variations, 

 and that there were times when tracts of sand were exposed 

 and dried in the sun, and on these the strange reptiles of 

 the period have left their footmarks. It was also princi- 

 pally during such times of partial desiccation that the beds 

 of rock-salt and gypsum were deposited by precipitation 

 from the saline waters. 



That at least one island existed in the lake is proved by 

 the relations of the Rhsetic and Liassic beds to the Dolo- 

 mitic conglomerate in the Mendip district, the newer beds 

 overlapping the conglomerate along the flanks of these hills, 



