564 Mr. J. Beete Jukes and the Rev. Saiiuel Haughton on 



PART I. 



The Geological Relations of the Lower Palaeozoic Rocks. 

 By J. Beete Jukes, M. A., F. R. S., &c. &c. 



Page. 



I. Stratified Rocks oe Fobmations, 564 



II. Igneous Rocks, 567 



III. Period of Action of Disturbing and Denuding Forces, 570 



IV. Position and Lie of the Rocks, 572 



A. The Wexford Cambrian District, 573 



B. The Cambrian district of North Wicklow, 574 



C. The Howth Cambrian District, 575 



D. The Cambro-Silurian Area of Wicklow, Wexford, and Waterford, 575 



E. The Cambro-Silurian Area of Kildare and Wicklow, 582 



F. The Main Granite Area, 583 



G. The Carnsore Area, 585 



V. Cleavage, 586 



The district which we propose to describe consists of the two counties of 

 Wicklow and Wexford, with the adjacent parts of the counties of Dublin, Kil- 

 dare, Carlow, Kilkenny, and Waterford. It is defined on the land side by an 

 irregular line running from Howth Harbour to Ballyvoyle Head near Dungar- 

 van, that line forming the boundary between the upper Palaeozoic formations 

 on the one hand, and the lower Palaeozoic rocks on the other. 



I. Stratified Rocks or Formations. 



The lower Palgeozoic rocks of the south-east of Ireland belong to two geo- 

 logical periods — the Cambrian, and the Cambro- (or Lower) Silurian.* 



1. The Cambrian rocks consist of a great series of alternations of sand- 

 stones, or gritstones, and slates, having a total thickness of many thousand feet. 



• We think it advisable to adopt the distinctive term Cambro-Silurian (first suggested by 

 Professor Phillips), in order to show that it is very distinct from the (so-called) Upper Silurian, 

 and that they are not mere subdivisions of one formation, like upper and lower Lias, or upper 

 and lower Chalk, but as distinct as Carboniferous is from Permian, Oolite from Cretaceous, &c. 



1 



