THE DEVONIAN PERIOD. 



443 



connected beneath younger beds. The Devonian system is also much 

 more widespread in western Europe than its present outcrops indi- 

 cate. 



Fig. 203. — Section of the Devonian system of Dinant and Namur. 1 = Cambrian and 

 Silurian ; 2 = Lower Devonian ; 3 = Upper Devonian ; 4 = Carboniferous limestone ; 

 5 = Coal Measures; /, fault. (Barrois.) 



The British Isles. — In the British Isles the Devonian formation 

 has two phases. The first is found in southwestern England in the 



Fig. 204. — Section through the coal-field of Charleroi. 1 = Lower Devonian; 2= 

 Upper Devonian; 3 = Carboniferous limestone; 4 = barren, and 5= coal-bearing 

 Carboniferous formations. The heavy black lines indicate faults and overthrusts 

 (Briart.) 



area which gave the formation its name 1 (Devonshire). Here the 

 system has a thickness of 10,000 or 12,000 feet, and, as shown by its 



Fig. 205. — Section showing the coal-bearing formations, (C), beneath Devonian (D) and 

 Silurian (S). M=Lower Carboniferous; C= Coal-bearing formations. (Pas- 

 de-Calais; Barrois.) 



fossils, is of marine origin. The structure of the Devonshire Devonian 

 is so complicated that it is much less well calculated to furnish a key 



1 The name Devonian was first used by Sedgwick and Murchison in 1839. Trans, 

 Geol. Soc, 2d series, Vol. V, p. 688 ? 



