^^^- 55-] STKFCTURE OF THE SOUTHERN MALVEKNS. 139 



length, is composed of HoUybush Sandstone, but the north-western 

 corner of the hill consists of May Hill Sandstone. 



The Hollybush Sandstone is separated from the Archsean Series 

 by a northerly prolongation of the fault that runs down the north- 

 western corner of Eagged stone Hill. This fault forms no feature in 

 the landscape, and its apparently straight course across the contour- 

 lines indicates that it is practically vertical. That the junction is 

 really a fault follows from the dip of the sandstone behind the 

 cottage on the northern side of the Hollybush Pass ; the beds here 

 strike directly towards the gneissic series. The Hollybush Quartzite, 

 moreoYer, as on the western slope of Raggedstone Hill, appears to 

 be absent along by far the greater part of the line of junction, but 

 at one point a brecciated quartzite (M 173 a),^ in places impregnated 

 with heavyspar, is exposed. This has, so far, yielded no fossils, but 

 its close lithological resemblance to the Hollybush Quartzite, as seen 

 in hand-specimens and under the microscope, shows that it belongs to 

 the Hollybush Series. At a distance of 1 or 2 feet from this rock 

 the Hollybush Sandstone is exposed, apparently dipping at an angle 

 of 20° west-north-westward, and abutting against the quartzite, 

 from which it must, accordingly, be separated by a fault. 



The May Hill Sandstone at the north-western corner of the hill 

 was evidently noted by PhiUips, who remarks that there are traces 

 of ' Caradoc ' Sandstone between the Obelisk and Midsummer Hill.^ 

 Debris from this patch are abundant, and furnished a variety of 

 fossils, among which the following were recognized : — StricJclandinia 

 lens, Sow., Sir. Ih^ata, Sow., Pentamerus oblongus, Sow., P. glo- 

 hosus, Sow. (?), ' Petraia,^ crinoid-stems, corals, etc. 



The beds are exposed in place, only at the extreme north- 

 western corner of the patch, where the dip is 45° eastward. 



These May Hill Beds are separated from the gneissic series by a 

 well-marked band of hard conglomerate and quartzite, which I 

 would propose to call the Hollybush Conglomerate and 

 Quartzite. It can be traced from the bed of the stream flowing 

 down the Gullet Pass, in a south-south-westerly direction, along the 

 western slope of the ridge of gneissic rocks forming the northern 

 extremity of Midsummer Hill, Its junction with this series is not- 

 marked by any depression or change of slope, but can be indistinctly 

 seen in the road, where, though somewhat irregular, it dips on the 

 whole east-south-eastward at 80° : the fault is, therefore, reversed. 

 Both series can also be seen in the bed of the stream. The junction 

 with the May Hill Sandstone is not exposed, but is indicated by 

 a small depression, along which runs a footpath from the road. 

 The conglomerate and quartzite are well seen in a small quarry 

 (M 170) near the roadside, where the beds dip north by west at 

 32° ; some of the layers here are crowded with fragments or whole 

 shells of Kutorgina, etc. At a point farther south the dip is- 

 apparently north 30° west at about 15° ; still farther south (M 366) 



1 [' 73 a ' on the map, PL XIII.] 



2 Mem. Geo]. Sm-v. vol. ii (1848) pt. i, p. 54. 



