OF THE COUNTY OF LEICESTER. J 3 



fine-grained clay slate. The finer portions have generally a well- 

 defined cleavage, or fissibility, in a certain direction that gives to the 

 rock its slaty character. The direction of this cleavage, or way in 

 which the rock splits into slate, is not along the beds, as would at 

 first be supposed, but across them, the same lines traversing the 

 whole of the beds from top to bottom. The original bedding of the 

 rock may be discovered by observing its variations in colour and 

 texture ; as where a coarse band may be traced between two fine 

 ones, or, where they exist, by the beds of organic remains. Bands of 

 different colours, technically called " the stripe," may be frequently 

 observed, which are always parallel to the true beds, and by their help 

 the real dip of the strata may be found out. Some general, but at 

 present obscure, agency has so acted upon these rocks as, some time 

 after their formation, to have sealed up as it were their original beds, 

 and given the mass a tendency to split in other directions. Upon 

 this subject, however, I must refer the reader to Professor Sedg- 

 wick's paper on the Ci Alterations produced in Rocks after their For- 

 mation," in the third vol., N. S., of The Geological Transactions. 

 The slate rocks of Charnwood Forest are frequently associated with 

 porphyries, which occur either in beds or in irregular masses ; and 

 over all the north west portion of the district, the porphyries or igne- 

 ous rocks are by far the most abundant material, having almost en- 

 tirely usurped the place of the aqueous rocks, and altogether obscured 

 their stratification. This is the case with Bardon Hill, and the hills 

 north and east of Whitwick. In the other parts of Charnwood 

 Forest, however, the dip or inclination of the strata is quite plain and 

 easily ascertainable by any one who has had the different lines of 

 cleavage, stratification, and joints clearly pointed out to him.* By 

 an examination of the district, it will be seen that a little north of 

 Bradgate Park, and between the hill called Old John and Swithland, 

 there is a valley called Lingdale, which runs a little west of north 

 and east of south. A line drawn along this valley and continued each 

 way, will divide the Charnwood Forest district into two unequal parts, 

 the largest being that to the south west of the line. Now the rocks 

 of which these two parts are composed dip in opposite directions — all 

 those lying to the north east of this line dipping to the north east, 

 and those lying to the south west of it dipping south west.f This 



" My own knowledge of this district, and of the north of the county 

 generally, was gained in the autumn of lfi.'<7, in an excursion, during which I 

 had the advantage of the tuition of Professor Sedgwick. 



•f- See section No. .'(. 



