514 



GEOLOGY. 



iferous (Mississippian) period, even in western Europe. Limestone 

 denotes clear seas; but the borders of clear seas are often the sites 

 of accumulation of clastic rocks, and the clear waters of the early 

 Carboniferous sea which extended from Ireland to the north of Europe 

 were bordered by shores along which mud, gravel, and sand were deposit- 

 ing. In the north of Britain, for example, near the northern borders 

 of the sea of the period, there are shales and sandstones, and the same 



Fig. 234. — Map showing the relations of land and water in France in the early 

 Carboniferous period. (De Lapparent.) 



is true in the south of England along the southern border of the same 

 sea. This facies of the formation corresponds, in a general way, with 

 the Culm of the continent, and is sometimes known by the same name. 

 The Culm phase of the Carboniferous often contains conglomerates, 

 and locally coal. 1 Beds of marine limestone frequently overlie the 

 Lower Carboniferous coal-seams of Scotland. 



^eikie, Text-book of Geology, Vol. II, pp. 1045-1051. 



