PRECARJ30NIEER0US ROCKS OF CHARNWOOD FOREST. 231 



under the microscope, the prevailing colour of the other rocks of 

 this district is due. A slide of the normal rock consists of felspar, 

 rather decomposed, but chiefly, so far as can be ascertained, plagio- 

 clase, a little quartz, mostly interstitial (an approach to graphic 

 structure being sometimes shown), a fair amount of hornblende, 

 some rather fibrous, some characteristic, and of magnetite, often in 

 well-marked crystals. In the slide exhibiting both varieties there 

 seems to be a slight difference in texture just along the line of 

 junction ; and near it in the red variety is a patch or two of 

 calcite, with some rosette-shaped aggregates of chlorite. These are 

 not common in the Forest rock, where the isotropic viridite is the 

 more usual decomposition product. This rock, then, is rather a 

 quartz diorite than a syenite. 



We see, then, that these rocks, which are probably only the 

 projecting summits of a much more extensive tract, are obviously 

 long anterior to the Trias, and are doubtless part of the same phy- 

 sical system as the Forest. 



Lithologically, also, they are closely related to the syenites of that 

 district, though plagioclase felspar is a little more abundant, and 

 the crystalline condition of the patches nearest to the Forest is 

 rather different. The latter distinction, however, is not of much 

 importance. All things considered, notwithstanding the dioritic 

 character of the Barrow-Hill massif, we are of opinion that their 

 chronological relations are with the Charnwood syenites rather 

 than with the Warwickshire diorites (which are only eight miles 

 from Sapcote), so that they may be safely assigned to a period ante- 

 rior to the Carboniferous. Our recent discovery of the slate at 

 Enderby, described above (p. 227), confirms us in this opinion, so 

 that the whole length of the area occupied by or resting upon the 

 Forest rocks, measured from north to south, is not less than seventeen 

 miles. 



Faults oe the Forest Eegiok. 



It will have been seen from the first part of this paper that the 

 beds of Charnwood Forest have been much dislocated. The exact 

 course of the dislocations can hardly ever be traced, or their 

 amount with any accuracy ascertained. The only exception is 

 the great fault running along the anticlinal axis. This passes 

 from Whitehorse Wood on the north by Ives-Head Lodge, down 

 the valley between Ives Head and Shortcliff, and leaves Charley 

 Knowl on the west. Its position with reference to Bawdon Castle 

 is not known, but the syenite there may well have come up through 

 it as a line of weakness. It appears to pass between Black Hill 

 and Green Hill, skirts the east side of Benscliff Wood and the west 

 corner of Blores Hill, crosses the corner of Bradgate Park about a 

 quarter of a mile from the Holgate Lodge, and disappears under the 

 Trias. 



At the northern end the beds on the eastern side are below those 

 on the western so far that the whole series of the Charley and Ives- 

 Head rocks are invisible. The thickness of these beds cannot be less 



