7G4 E. HILL AND T. G. BONNET ON THE 



bed at Blorc's Hill. These greenish mottled ashes, as we have called 

 them, are difficult to describe. They contain glittering felspar crys- 

 tals, pinkish felstone, and smaller pieces of the fine slate, of which all 

 the large fragments (so far as we have seen) are composed. Some 

 of the last are two or three feet long. The bed is also well ex- 

 posed at tho col connecting this hill with Old John, just by the 

 usual path to the summit. There are many segregation-veins of 

 white quartz, as is not seldom the case in these agglomerates. The 

 slate fragments are much indurated, of the usual pale greenish- 

 grey colour, and almost fiinty texture ; some are distinctly bedded. 

 They lie in all directions ; and the cleavage-planes of the bed itself 

 can be traced, though imperfectly, through them. One piece, bent 

 almost into a quadrant, is about 4 feet long. Tho general aspect of 

 the matrix suggests that it has consisted of an ash not rich in silica, 

 such as that of an andesite. The dip of all the beds we have de- 

 scribed is southerly, usually about 30°, but sometimes as much as 

 50°. The dip of the beds on the col, where they can be seen, is in 

 the same direction ; but the strike of the great agglomerate bed is in 

 a line with that of the smaller one first described above. "We have 

 little doubt that a fault with a throw of some 50 or GO yards has 

 shifted the Holgate beds about 120 yards forward from these. 



The section up the south spur of Old John is of much the same 

 nature. It begins with banded slates, some so fine and hardened as 

 to be almost porcellanites. One bed is an exceedingly compact grey- 

 ish-green rock with dark green spots (? hornblende), a subconchoidal 

 fracture, and not very conspicuous cleavage, one of the finest-grained 

 rocks in the Forest. After these come coarse ashes, and on the 

 summit a bed of not very coarse agglomerate, followed again by 

 banded slates. The great agglomerate bed, which can be traced along 

 its strike up the greater part of the east spur, is lost sight of at the 

 top. The line of strike passes through a plantation where no rocks 

 can be seen ; but as the last outcrop shows the rock rather shattered, 

 there is possibly another fault. 



Descending the hill northwards we see no more exposures till we 

 quit the park by the footpath, through a small spinney, w T hich in the 

 Survey map is coloured red and marked F. Very few rocks are to 

 be seen ; but those are curious. AVe have first at the east end a 

 little patch of well-marked banded grits dipping, as usual, south. 

 They are rather too coarse to be called slates, indicating bands bj r 

 weathering rather than colour. Underlying these are a set of rocks, 

 without visible stratification, isolated, but no doubt in situ, and the 

 relics of a bed of highly altered pale greenish crystalline-looking 

 rock, containing a good many felspar crystals, a few small grains of 

 quartz, and some fragments of slate. Examined microscopically it 

 is seen, as we shall show, to be pyroclastic and altered. On a 

 line of strike below this, at the west end, is a bed of felspathic grit, 

 rather resembling felstone — and below this again fine-grained green 

 slate, the dip of which can be detected with a little trouble, and is 

 also south. 



Quitting the spinney and going down to the lane, we find in the 



