§ 6. DEVONIAN OF THE CONTINENT AND AMERICA. 757 



stone. Two of the finest harbours in Britain, or the world, 

 belong to this formation — Milford Haven, in South Wales, 

 and the Bay of Cromarty ;"* the latter, Mr. Miller's re- 

 searches and writings have made classic ground to the 

 geologist. 



The predominating colour of the sandstones and con- 

 glomerates has probably been derived from the red granitic 

 gneiss which forms chains of precipitous ridges in the north 

 of Scotland. This rock contains hsematitic iron-ore, dif- 

 fused as a component of the stone throughout its entire 

 mass ; and this metal also occurs in insulated blocks of 

 great richness, and in thin filiform veins, f 



6. Devonian of the Continent and America. — In 

 the Bhenish provinces and adjacent districts of Germany, 

 Devonian strata underlie the carboniferous system, and. 

 may be traced around, and dipping under the coal-field of 

 Westphalia.J 



In Russia, according to the researches of Sir R. I. Mur- 

 chison, the Devonian system extends over an area of 1 50,000 

 square miles, a region more spacious than the British Isles ; 

 and yet, throughout this vast superficies, the subdivisions 

 of the system are as distinctly characterized by their re- 

 spective fossils as in the disturbed districts of our own little 

 island. || 



In North America, the Devonian deposits appear in a 

 very prominent and characteristic form ; surrounding each 

 of the great coal-fields of the United States. The Silurian 

 rocks, which are largely developed in those countries, are 

 more or less overlaid by shales, sandstones, and flagstones 

 of this system; and these are surmounted by red sand- 

 stone, containing remains of the fishes and shells peculiar 



* Miller's Old Red-sandstone, p. 205. 

 f Ibid. p. 248. 



X Prof. Sedgwick and Sir R. I. Murchison. 



; Sir R. I. Murchison's Geology of Russia. 



3 d 2 



