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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



[June 9, 



perfect maimer, yet this is not in all instances the case. The mineral 

 nature of the limestones seems to have a considerable effect on the per- 

 fection of the jointing. There are series of thin-bedded cherty lime- 

 stones intercalated with the ordinary limestones, more particularly 

 near their base. In the neighbourhood of Cork, these are seen on 

 the Western road, in a small quarry east from Carrigrohnane. They 

 also make their appearance in the old quarry at Glasheen, and, S.E. 

 from this, at Summerstown. In the cutting on the Cork and Bandon 

 Railway, contiguous to the Cork Station, they likewise occur. Near 

 the Gasworks, immediately adjoining the south side of the road which 

 runs south of this quarry, they present themselves ; and also near the 

 South Infirmary. 



At this last locality, the thin-bedded limestones have masses of 

 red chert in them, which put on much of the aspect of jasper. Beds 

 of a like cherty character, and containing masses of white chert, 

 may be seen in the cutting of the Cork and Passage Railway, at the 

 first bridge south of Black Rock Station; from this they extend 

 eastward, and are again seen at Little Island, immediately south of 

 the quarries which are now worked there. A red limestone in some 

 instances marks these cherty bands ; and, where this is the case, the 

 general E. and "W. strike of the limestone-strata is well manifested. 

 In all instances, however, where the cherty limestones occur, they 

 afford evidence of the strike of the Carboniferous limestone con- 

 forming with that of the underlying Devonian rocks. In these cherty 

 limestones, jointing is far from being well shown. The north and 

 south courses are apparent; but these are generally more remote 

 from each other than in the ordinary limestones. The horizontal 

 series is seldom exhibited, and the oblique series is equally absent. 



At Summerstown, previously referred to, there are two quarries, 

 which are not more than a hundred yards from each other. The 

 one on the south-east exhibits the limestones intersected with the 

 three courses of jointing, and has all traces of stratification oblite- 



Fig. 7. — West face of the Glasheen Quarry, showing the ordinary 

 jointed Limestone on one hand, and the bedded and not-jointed sili- 

 ceotis Limestone on the other. 



Sihceous hmestone 

 devoid of jointing. 



Ordinary jointed Hmestone. 



