1866.] JUKES OLD BED SANDSTONE AND DEVONIAN. 331 



Lismore to Knockadoon Head on the south side of Youghal Bay, and 

 spreads to a breadth of 36 miles towards its western extremity, mea- 

 suring from Rossbehy in Dingle Bay to Sheeps Head on the south 

 side of Bantry Bay. Its southern as well as its northern margin is 

 formed by a continuous ridge of Old Bed Sandstone, stretching across 

 Ireland from sea to sea, forming Sheeps Head on the west and Knocka- 

 doon Head on the east, the distance between them being nearly 90 

 miles. This large area of Old Red Sandstone is puckered into nume- 

 rous anticlinal and synclinal curves, the axes of which run nearly 

 east and west in its eastern portion, but bend to west-south-west and 

 east-north-east on its western side. These axes also rise and fall 

 frequently along their course, the lower beds rising out to the surface 

 where each axis rises, the higher beds taking the ground where the 

 axis falls. Not only do different beds of Old Bed Sandstone crop 

 up, then, as we trace the summit of an anticlinal curve, or take the 

 ground as we follow the hollow of a synclinal trough, but in the 

 latter case the Carboniferous Limestone is often brought in below 

 the present surface of the ground, and preserved as a limestone 

 trough. These limestone troughs run sometimes for many miles, 

 until the gradual rise of the axis of each synclinal brings the lowest 

 limestone beds to the surface, and in its prolongation the synclinal 

 curve is traceable only in the Old Red Sandstone. 



Towards the East we have first the limestone trough of Rath- 

 cormacJc, Tallow, and Aglish, about 24 miles long; secondly the 

 small trough of Clashmore, only two miles long. Both these seem to 

 terminate eastwardly in faults which jump the Old Red Sandstone 

 up above the level of the limestone in the same line of strike. 

 Thirdly we have the trough of Youghal and Ardmore, about 10 miles 

 long ; fourthly comes the long trough of Midleton and Cork, which 

 runs westwardly from Youghal Bay to Cookstown, a distance of 

 55 miles*. North of the extremity of this are the minor Carboni- 

 ferous troughs of Riverstown, Blarney, Ardrum, Coachford, and 

 Annaghallagh (the latter a little south-west of the town of Macroom), 

 all nearly on the strike of the Ardrmre and Youghal trough. To 

 the west of the Annahgallagh trough the undulations do not bring 

 in any beds superior to the Old Red Sandstone itself, for a length 

 and width of upwards of 20 miles between Dunmanway and Mill- 

 street. A great thickness of Old Red Sandstone is exposed in this 

 tract, as the beds in some places dip steadily north or south at 

 angles of 50° or 60° for two or three miles continuously, clear 

 exposures of them being observable on the sides of barren hills bare 

 of drift. These sections show a thickness of 5000 or 6000 feet in 

 the body of the formation, without reaching either the uppermost 

 or the lowermost beds, and such sections are of no unfrequent 



* In a hasty traverse of the country about Pembroke and Tenby, I was struck 

 by the great similarity both in the physical geography and geology of that country 

 to that of the Cork and Youghal district. Mr. Salter, in his paper " On the 

 Upper Old Ked Sandstone and Upper Devonian rocks," notices the identity of 

 the beds of Pembrokeshire and South Ireland (Quart. Journ. Geol. Soc. vol. xix> 

 p. 474 et seq). 



2x2 



