154 



PEOF. T. T. GROOM ON THE GEOLOGICAL [May 1 899, 



other. The schists commonly dip towards the axis of the hill, as 

 also do the inverted Black Shales, and sometimes the Hollybush 

 Sandstone. The schists in the large quarry at White-leaved Oak 

 show clearly a series of small folds overthrown to the west, and 

 it may be seen that they are traversed by a small reversed fault. 



Taking into consideration this disposition of the schists, together 

 with the inversion of the Black Shales, I would suggest that evidence 

 here exists of an overfold towards the west, the Archaean strata 

 having been thrust over the Cambrian Series, with the result that 



Fig. 19. — Diagrammatic view of the structure of Midsummer Hill. 



i^F= Faults. 



cZ= Black and Grey Shales (Cambrian) 



i^'i^' — Fault between Trias and 



c = Hollybush Sandstone. 



Archaean. 



6= Hollybush Quartzite and Con- 



^ = Trias. 



glomerate. 



/=Haffield Breccia. 



<2 = Archaean. 



e=Maj Hill Beds. 



.ra^= Present surface. 



new planes of schistosity were introduced in the former. The fold 

 was finally ruptured by a fault, which probably was nearly vertical. 

 The disposition and relations of the Hollybush Sandstone, how- 

 ever, need further elucidation. This, as already shown, is probably 

 thrown into a smaU. overfold, the axis of which dips towards the 

 west, as also does in some cases the fault-plane between it and the 

 schiats. Figs. 4, 5, 6, & 7 (p. 136) illustrate this arrangement, I 



