Lower Palceozoic Rocks of the South-East of Ireland. 575 



parallel to the south-eastern boundary of the adjacent main district. The beds, 

 which consist of quartz rock interstratified with brown and purple slates, are 

 apparently vertical, or nearly so. 



The north-westerly outlier is much smaller, being not more than a mile and 

 a half long, by a third of a mile in width. It is called Carrickgolligan on the 

 Ordnance map, but is also known as Shankill. It rises to a height of 912 feet, 

 both beds and boundaries striking N. 42' E., or N. E. and S. W. 



C. — The Howth Cambrian district is nearly circular, and from two to three 

 miles in diameter. It consists of great beds of quartz rock interstratified with 

 green grits and green and purple slates. The beds are always highly inclined, 

 but strike in such various directions with so much contortion and confusion as 

 to render any further general statement as to their position impossible. They 

 may be seen crumpled in a most remarkable way on the little island of Ireland's 

 Eye, with the black slates of the Cambro-Silurian series obviously unconform- 

 able to them. 



The irregularity and confusion to be observed in these Cambrian areas, and 

 the impossibility of reducing them to order, and determining the original posi- 

 tion and total thickness of the beds, arises, doubtless, from the number and mag- 

 nitude of the disturbances by which they have been affected. When we recol- 

 lect that they were already highly inclined, and greatly denuded and disturbed, 

 before the deposition of the Cambro-Silurian rocks, having perhaps a general 

 strike quite different from that subsequently impressed upon the district; and 

 that, after the Cambro-Silurian beds were deposited horizontally across the 

 edges of these highly inclined Cambrian rocks, both were affected by disturbing 

 forces which have set the Cambro-Silurian rocks themselves into highly inclined, 

 often into vertical, positions, and affected them with great dislocations, and 

 probably with many complicated flexures, — we shall be at no loss to imderstand 

 the difficulty of the attempt to unravel the confusion thus produced in the 

 older of the two formations. 



D. — The Cambro-Silurian area of Wicklow, Wexford, and Waterford, is the 

 largest and most interesting of the seven into which our district is divided ; 

 and might be said to include areas A and B. It is more than 100 miles in 

 length from Killiney to Ballyvoyle Head, with an average width of fifteen or 

 twenty miles. 



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