124 NEOZOIC TIME. [CHAP. Till. 



strata belong to the Old Eed Sandstone, and not to the 

 Trias. 



Northward the Keuper beds extend far beyond the 

 limits of the Bunter. In Cumberland and the north-east 

 of Ireland their characters are similar to those of the 

 Midland counties, but on the west coast of Scotland the 

 strata are rather different. Their thickness here varies 

 considerably, but in Mull, Mo'rvern, and parts of Ross it 

 is about 1,000 feet, and the whole probably belongs to the 

 Keuper. The lower part consists of coarse breccias, con- 

 glomerates, and sandstones, and the upper half exhibits a 

 variable succession of red marls, with bands of concre- 

 tionary limestone and of hard white or greenish sand- 

 stone. The breccias and conglomerates were doubtless 

 accumulated in the same manner as those of Devonshire, 

 and the higher beds seem to have been deposited in the 

 quiet waters of a lake. 



2. Geographical Restoration. 



The unconformity which exists between the Dyas and the 

 Trias, wherever the latter rests on the former, points to a 

 period of elevation and disturbance, which probably in- 

 volved the total desiccation of the Dyassic seas and lakes, 

 and the conversion of their floors into wide tracts of dry 

 desert land. The only beds in England which appear to 

 be of intermediate age are certain deposits of rock-salt, 

 gypsum, and limestone, which have been found below the 

 Trias in deep borings near Middlesbrough-on-Tees. The 

 limestones contain Dyassic fossils, but lie between beds of 

 rock-salt, the upper of which seems to be conformably over- 

 lain by Trias sic sandstones ; none of them appear along the 

 outcrop, and they must, therefore, occupy a limited area. 

 They may have "been formed in one of the restricted lake- 

 basins which doubtless existed during the gradual drying 



