588 GEOLOGY. 



the existence of glaciers; 1 but this interpretation cannot be looked 

 upon as established. Other interpretations, such as the transporta- 

 tion of bowlders by uprooted trees floated out to sea, are tenable. 



Though the Coal Measures are widely distributed on the continent, 

 the areas where they are exposed are relatively small, as compared 

 with those of America. It is not in all cases possible to say whether 

 the detached areas are the dissevered remnants of areas which were 

 once extensive, or whether they are but parts of areas which are still 

 continuous, though largely buried by younger beds. The system 

 appears at the surface in relatively large areas in Belgium and northern 

 France, and in small areas in southern France, and the Iberian penin- 

 sula. It is also known at many points in the mountain regions of 

 central Europe, and has great development in Russia. 



North of the European continent, the Carboniferous formations 

 (Fusulina limestone, Coral limestone, etc.) are represented in some 

 of the Arctic islands (Spitzbergen, Nova Zemla, Bear Island). 



Thickness. — The Coal Measures of Europe attain great thickness, 

 being 8000 feet (13,500 including the Millstone grit) thick in Lan- 

 cashire, and several thousand feet in many parts of Great Britain 

 and Ireland. These extraordinary thicknesses of sedimentary rock 

 in Great Britain must mean the presence close at hand of somewhat 

 extensive and high land areas. 2 The corresponding strata attain a 

 thickness of 10,000 feet in western Germany, where they contain much 

 coal. 



Igneous rocks and crustal disturbances. — The granites of the Harz, 

 Thuringerwald, Black Forest, Vosges, and other mountains of central 

 Europe, appear to date from the end of the Early Carboniferous, 

 though the eruptions probably continued into the Later Carboniferous. 

 Various sorts of igneous rocks are associated with Upper Carboniferous 

 formations of sedimentary origin in Brittany, Scotland, some parts of 

 England (Cornwall), and Scandinavia (near Christiana). 



The extrusion of these igneous rocks seems to have been an accom- 

 paniment of the crustal disturbances which were in progress during 

 the period. In middle and western Europe, these disturbances began 

 at the close of the Early Carboniferous, as already noted (p. 516), and 

 continued through the Permian. The truncated remnants of the western 



1 Ramsay, Quar. Jour. Geol. Soc, 1855, p. 185. 



2 Geikie, Text-book of Geology, 4th ed. p. 1047. 



