OF THE COUNTY OF LEICESTER. 15 



now to take a hasty glance at the history of the causes which pro- 

 duced these materials and placed them in those positions. 



To begin, then, with the lowest, and therefore the oldest rocks, 

 which are found in the county, the slates namely of Charnwood Fo- 

 rest, we see that a great sea once existed over this portion of the 

 globe, at the bottom of which there was deposited a vast amount of 

 earthy sediment. This sediment was gradually accumulated, since it 

 consisted of alternate beds of fine and coarse materials, successively 

 deposited, and not mixed up the one with the other. We know that 

 this sea was inhabited by various animals, for though none of their 

 remains have been found in the slates of Charnwood Forest, there 

 are abundance of them in the other portions of the same rocks which 

 form the mountains of Wales. This absence of organic life over that 

 portion of the bottom of this sea which is now visible in Leicester- 

 shire, may possibly be due to the action of volcanic causes, for along 

 with the aqueous rocks formed in it, we find beds of igneous rocks, 

 which we know to have been poured out in a state of fusion, like 

 great flows of lava, and to have been afterwards covered up by other 

 aqueous sediment. Great masses of these melted rocks were also in 

 some places protruded among and into the previously formed aqueous 

 rocks, so as sometimes to obliterate their stratified character. These 

 igneous rocks having cooled down under pressure, have become what 

 we term porphyry ; and the aqueous rocks having become indurated, 

 and having at some subsequent period been affected by a peculiar 

 agency, which has given them the property of fissibility in a certain 

 direction, are now what we call slate and slate rock. Giving to the 

 whole mass a general term, they are called Cambrian, because the 

 same rocks form a great portion of Wales. 



After the formation of these Cambrian rocks, there elapsed an in- 

 terval, of what length it is impossible to say, but sufficiently long to 

 allow of the accumulation in some localities of stratified rocks many 

 thousand feet thick, and for great changes to take place in the animal 

 and vegetable kingdoms of our globe. During this interval we have 

 no indications given us of the state of this particular district; either it 

 was dry land, or, if sea, no strata were deposited in it ; or lastly, if 

 strata were deposited, they have since been destroyed. 



After the lapse of this long period, however, whatever it may have 

 been, we again arrive at something certain, and find that sea existed 

 over at least a portion of the district, in which were deposited those 

 calcareous materials which now form what we call the mountain lime- 

 stone. This sea was full of animals, more especially Polypi, Radiaria 



