1824.] the Rocks of Mount Sorrel, 8$c. 13 



crystals, we find small angular fragments of quartz (base of 

 High Swanmore, &c.) which, when the surface of the imbedding 

 substance is somewhat decomposed into a white or greyish- 

 white and granular mass, of which the particles possess but little 

 cohesion, are left protruding. In other instances the fragments 

 of quartz are intermixed with the regular crystals of quarts* and fel- 

 spar (High Swanmore, &c). But the imbedded fragments gome- 

 times possess all the characters of the slate already described 

 as including irregular lines of chlorite, and as forming layers 

 between the other varieties of the rock (Morley Hill quarry), or 

 they resemble a reddish jasper which mostly is very hard, some- 

 times brittle (ridge of Bardon Hill), and occasionally other an- 

 gular fragments appear of less decided character. It is, how- 

 ever, manifest to us, that the imbedded substance occasionally 

 differs greatly from any of the preceding, in possessing altoge- 

 ther the appearance of some of the more- homogeneous and 

 greyish varieties of the rock itself, but much harder, and inclos- 

 ing transparent crystals of quartz, and occasionally of felspar ; 

 these occur in nodules, varying from the size of a nut to several 

 inches in diameter (Chamber Hill, Pedler Hill, ridge of Bardon 

 Hill) ; and though they may be separated from the rock from 

 which they project owing to the progress of its decomposition, 

 yet there does not appear to be any precise line of separation 

 between them; these, therefore, we consider to be of contem- 

 poraneous formation with the rock itself, as also may those 

 numerous specks and patches be, which at first sight appear like 

 imbedded fragments, but in reality present no line of separation 

 from the rock itself, and are generally harder ; they are of various 

 colours, grey, brown, or red (S W foot of Beacon Hill, Hi°-h 

 Sharpless, Little Gun Hill, &c.) 



The paste of these porphyries consists of all the varieties of 

 the slaty rocks already described; but occasionally is much 

 harder than any of them, since it resists the knife completely, 

 owing, as we assume, to the mechanical diffusion of silex abun- 

 dantly throughout the mass, which then partakes little or not at 

 all of the schistose character (base of Windgate Hill, Pedler 

 Hill, 8cc.) and resembles hornstone or compact felspar. 



In regard to the actual stratification of the rocks of Cham- 

 wood Forest, two opposite appearances claim attention. 



It has been mentioned that the direction of the cleavage of 

 the slates and slaty rocks is everywhere nearly the same ; that 

 the edges of the slates uniformly run within a point or two of 

 N W by \V, and SE by E ; and that the only difference is 

 apparent in their more nearly approaching N W and SE. It has 

 also been mentioned, that in the largest quarry near Swithland, 

 a seam of the best slates runs in this direction, and parallel with 

 it a seam or vein of rock, quite different from the slate ; that in 

 the quarry close to Woodhouse Eaves, a seam or vein of talc 



