710 GEOLOGY. 



eminences. This circumstance, Mr. Phillips states, " is probably not explicable by the 

 mere wasting of these soft rocks by floods of water, but due to some law of physical 

 geology yet unexplained. We can only conjecture that it is connected with the repose 

 of subterranean forces, which prevailed after the violent commotions of the coal strata over 

 nearly all Europe, till the tertiary epoch." A few elevations occur at the height of 800 

 feet above the level of the sea, Ashley Heath, Brandon Mount, and Barr Beacon ; but 

 the average altitude of the hills is much lower. Some of the finest pastures in the king- 

 dom are included within the range of this formation. The cereal grasses and leguminous 

 plants flourish luxuriantly upon the red marls, while the soil formed by the magnesian 

 limestone, though usually considered unfertile, is favourable to the growth of various 

 timber-trees, the oak, elm, and walnut, and especially suits the yellow rose and sweet- 

 scented violet. 



The system is but scantily developed in Scotland, except on the borders of the Solway 

 Firth, where it occurs in force, occupying also a considerable area in the north of Ireland. 

 It comprises an immense extent of the continent of Europe, appears conspicuously in the 

 countries watered by the Rhine, the Danube, and the Volga, and composes many of the 

 river valleys of the United States. Without going through the beds of the formation 

 consecutively, a few prominent or peculiar rocks of the series are selected for a general 

 notice. 



Sandstone. This is occasionally a fine-grained quartzose rock, forming a hard grit, 

 of sufficient cohesion to be useful for architectural purposes. The grains seem covered 

 externally and cemented together by the red oxide of iron, as if they were the ruins of a 

 mass of pure quartz, much ground down, and deposited in waters, having a strong ferrugi- 

 nous impregnation. But frequently the sandstone is a coarse conglomerate, composed of 

 pebbles of various kinds, very slightly cemented, and hence easily excavated into artificial 

 caverns, and of little value as a building stone. This is the case with the sand rock of 

 the town and castle of Nottingham, consisting of rounded pebbles of quartz, granite, 



porphyry, and slate, which have 

 either been derived from the 

 Charnwood Forest Hills, or from 

 identical rocks connected with 

 that range, which have been 

 completely worn away. The ar- 

 rangement of these pebbles in 

 the castle-rock indicates the state 

 of commotion in which they were 

 aggregated. The sandstone of 



^mgmnm'msmim.ML. * V> \ I < % ^ this locality is remarkable for its 



numerous caverns, which are all 

 probably artificial, or, if natural, 

 have been enlarged, and received 

 their present- shape from human 

 labour, the soft and friable na- 

 ture of the rock admitting of an 

 easy excavation. This circum- 



Nottingham Castle. ,. 



stance, according to some etymo- 

 logists, has given its name to the town, and through it to the county, a derivation from 

 the Saxon snodengaham, signifying the house of caverns." Similar caverns occur in 

 the same strata, but upon a smaller scale, at Guy's Cliff, near Warwick, and at Knares- 

 borough in Yorkshire. 



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