132 



PROF. T. T. GROOM ON THE GEOLOGICAL [Maj 1899^ 



such as is not attempted here. I have, therefore, contented myself 

 •with representing on the map (Ph XIII) the ohserved strikes and 

 dips of the gneissic series. 

 These dips, as indicated pig. 1. — Diagrammatic plan of the struc- 

 ture of the north-western corner of 

 Raggedstone Hill, and of the south- 

 western part of Midsummer Hill. 



in the map, frequently 

 show a marked relation 

 to the direction of the 

 axial fault, the schists 

 generally dipping away 

 at a considerable angle 

 towards the eastern side, 

 and the strike conform- 

 ing more or less closely 

 to that of the curving 

 fault. 



The exact position of 

 the line of junction with 

 the Trias is difficult to 



determine, as no expo- ^bS 



HbS 







, ' -Q(Mma\ 



"Sch 



•Ign 



sures of the latter are 

 seen close to the hill. 

 It must, accordingly, be 

 fixed chiefly by the cha- 

 racter of the slope ; for 

 here, as elsewhere along 

 the range, the steep slope 

 formed by the Archaean 

 rocks gives place lower 

 down to the much gentler 

 slope of the Triassic 

 area. The character of 

 the soil occasionally af- 

 fords assistance. 



The western half of 

 the hill is more complex 

 in structure. The higher 

 portions are formed, for 

 the most part, of a strip 

 of gneissic, schistose, and 

 massive rocks, which may 

 be traced from the road 

 in the Hollybush Pass to 

 that in the ' Valley of 

 White-leaved Oak.' 



North of the contour- 

 line of 800 feet the 



gneissic series is not exposed, and its presence is revealed only by 



debris and by excavations, but schists and gneisses appear to have 



been observed along the line by Holl.^ The series can, however, be 



1 Quart. Journ. Geol. See. vol. xxi (1865) p. 75. 



Ui/i/i- 



[Scale : 6 inch( 



Black Shale. 

 Hollybush Sand- 

 stone (outcrops). 

 Grrey Hollybush 

 Sandstone. 



The Hollybush Sandstone and Black Shales are 

 traversed by igneous rocks {Ign., cross-hatched). 



B.Sk. : 

 Hb.S.- 



Hh.S'.: 



QfM244] 



= 1 mile.] 



Q. — Quartzite 

 (black). 

 Sch. = Archasan. 

 i^i^.= Faults. 



