DEVONIAN AND OLD RED SANDSTONE SYSTEM 241 



600 feet of the Devonian an- hard quartzitic grits and slates of 

 tin- Plougastel and Glengarriff facies, but from their much smaller 

 thickness we may conclude that the Atlantic land did not reach quite 

 so nrar to Spain as it did to Brittany, the coast-line probably curving 

 away to the west 



Returning to England it may be noted that rocks containing 

 Upper Devonian fossils have been found in borings at Turnford, 

 near Cheshunt, and below London, but they do not help much in 

 our present quest. In the Ardennes, however, we find definite 

 evidence of the position of the coast-line in Lower Devonian time, 

 for the entire absence of the Lower Series in the basin of Nan air 

 proves it to have been land while that of Dinant was covered by 

 the Lower Devonian Sea. 



Here it must be pointed out that the supposed existence of 

 land to the south of Dinant and Fepin, with a narrow strait 

 between it and the northern mainland, is founded on a mis- 

 apprehension of the facts. There was land there in Silurian times, 

 and the basal conglomerate and sandstones of the Devonian testify 

 to its destruction, but there is no overlap of successive stages 

 against a slope of older rocks, and there can be little doubt that 

 the whole mass of the Lower Devonian strata in the basin of 

 Dinant passed over the massifs of Rocroi and Charleville ; in other 

 words, that this land of Silurian and Ordovician time sank beneath 

 the waters of the Devonian Sea. 



The same sea spread eastward over the greater part of Germany, 

 but the great thickness and sandy nature of the Lower Devonian of 

 the Harz Mountains testify to the proximity of land ; and when 

 we reach Poland still clearer indications are found, for there a 

 break and unconformity between Silurian and Devonian presents 

 itself, and we have in the Lowest Devonian deposits an intercalation 

 of marine strata with sandstones of the Old Red facies, as if a large 

 lagoon were being invaded by the sea. The same conditions are 

 present in Eastern Galicia, which must likewise have lain near the 

 margin of the continent, but in the Baltic provinces of Russia we 

 clearly stand on firm Devonian land (see p. 223). 



The line drawn on Fig. 80 to indicate the eastern border of this 

 continent is, of course, merely an approximation to its true course ; 

 at present we only know that the land did not extend into 

 Central Russia, and that it did not include Novaya Zembla. 



In Middle Devonian time there seems to have been a gem>rnl 

 suK-i-lence, enabling the Southern Sea to extend itself over some 

 of the southern and eastern portions of the northern continent. 

 Moreover, it seems that the areas invaded and covered by the 

 Eifelian Sea were of much larger extent in the eastern than in the 



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