DESCRIPTION OF GEOLOGICAL MAP. 465 



limestone appear under similar conditions. In Milford Haven, which is chiefly 

 flanked by Devonian rocks, Silurian deposits appear near St. Ann's Head; and 

 there are numerous isolated masses of Trap : Ramsey Island, and St. David's Head, 

 also consist of these igneous rocks. 



We now enter Cardigan Bay, which is formed in the lower division of the Silurian 

 system. The strata consist for the most part of slates with characteristic fossils, 

 which are associated with contemporaneous and intrusive igneous rocks. Mica and 

 chlorite schists, form the cliffs on the southern headland of Caernarvon Bay, and 

 similar rocks occur in the Menai Straits, and at Holyhead; with interspersions of 

 Devonian, Silurian, and Carboniferous strata. Along the coast of Denbighshire, the 

 Upper Silurian strata reach the coast, and are succeeded by Carboniferous and 

 Triassic deposits. 



Crossing the embouchure of the river Dee, which is situated in the Coal-measures, 

 the Triassic system of Cheshire appears at Birkenhead. Marine detritus and allu- 

 vium obscure the regular strata along this part of the Lancashire coast; until 

 beyond Lancaster Bay, where Upper and Lower Silurian strata, and Mountain lime- 

 stone appear. 



At St. Bees Head, the coast exhibits coal-measures, covered by Permian deposits; 

 and at Whitehaven and Workington, the sea-shores are entirely composed of carboni- 

 ferous strata, the beds of coal being worked far under the sea. At Maryport, the 

 magnesian limestone of the Permian system forms the cliffs. We now enter the 

 Solway Firth, and terminate this rapid sketch of the geological phenomena exhi- 

 bited by the coasts of England. 



H H 



