18 A POPULAR SKETCH OF THE GEOLOGY 



farther to limit the period of elevation of the coal field, and say that 

 it took place between the formation of the lower part of the new red 

 sandstone system and the upper of the same. Whether this would 

 be true of the Leicestershire district we cannot determine, since here 

 the lower portions of the new red sandstone are wanting, or at all 

 events not visible at the surface. We can, however, in Leicester- 

 shire point to one of the very agents which were accessary to all this 

 disturbance, namely the sienitic rocks before mentioned. These, in 

 their expansive struggles at escape, forced themselves while yet 

 molten masses through the cracks and fissures which were then pro- 

 duced in the inferior rocks, and having cooled under the pressure of 

 great depths of water or other materials, assumed the crystalline 

 structure which they now possess. The only anomalous circumstance 

 respecting them is, that they are on the outskirts of the Charnwood 

 Forest district, and not in its centre. 



Over the broken and irregular surface thus formed by these forces 

 of disturbance, a sea still flowed, which, upon tranquillity being re- 

 stored, deposited the level beds of sandstone and marl which form the 

 upper portion of the new red sandstone. These filling up the ine- 

 qualities, smoothed the whole over up to a certain height, leaving 

 only the highest portions of the previously existing rocks uncovered 

 by its beds.* 



After the deposition of all this red sediment, the sea became 

 again the dwelling place of numerous animals different from any 

 which had gone before them. Mollusca crawled upon its bed or 

 floated on its calmer surface, fishes sported in its waters, and the 

 terrific Ichthyosaurus was formed to dash through its stormy waves, 

 and reign the despot of the " ocean stream." At the bottom of this 

 sea, blue clay was now deposited, with occasionally some carbonate of 

 lime, forming the lias, in which has been preserved many a relic of 

 these creatures of the past, to tell us who and what preceded us in 

 the habitation of this globe of earth. After the formation of the 

 lias there elapsed another enormous interval, measured by the depo- 

 sition of the remainder of the secondary and the whole of the tertiary 

 formations, during which that which is now the county of Leicester, 



* Some portions of the red marls exist on the Hanks of Charnwood Forest, 

 at a height considerably greater than their general level; their position, how- 

 ever, may I think be easily accounted for, if we reflect that in a sea with an 

 uneven bottom, and in which depositions from above were taking place, some 

 portions of the sediment might in favourable situations be retained at much 

 higher levels than the general beds. 



