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classic investigations M. This is not the place to enter into the 

 many questions, among others the history of the origin of the 

 sheeted lava rocks, which are dealt with there. We will simply 

 recall that all these areas are generally considered, if not at 

 one time united, at least to have been much more extensive 

 than now, and that consequently the question of the origin of 

 the northern part of the Atlantic Ocean is most closely bound 

 up with the study of these basalts. As to the time of the for- 

 mation of the rock-mass itself, we know it was spread over a 

 long period; on Iceland the volcanic activity and formation of 

 basaltic rocks continues to this very day. But generally 

 speaking, the supposition is accepted that the bulk came into 

 existence during the Miocene period, the same epoch as that 

 from which, as we have seen, it has been assumed that the 

 bulk of the Arctic Tertiary plants derives. Our discovery at 

 C. Dalton of marine Tertiary formations of the Eocene age 

 (probably corresponding to the London clay and Bagshot Beds), 

 younger than a part of the true basalt formation, is thus not 

 less important for the question of the age of the basalts than 

 for that of the plant fossils. In this area at least the basaltic 

 eruption was in full swing already in Eocene times, an inter- 

 esting result, the application of which will be of the highest im- 

 portance for many geological questions touching the latest geo- 

 logical periods. However, 1 will not dwell on these points here, 

 but pass on to a short pétrographie description of the rocks 

 and the different localities. 



As we already know, the basalt occurs in two large areas 

 in E. Greenland, divided by Davy Sund and Scoresby Sund 

 and the gneiss mass of Liverpool Land lying between the two. 

 Both areas, as far as we know, are confined exclusively to the 

 coast, which they follow, put together, for a distance of at least 

 ten degrees of latitude. The southern area takes in a widely 



') J. Geikle: The Ancient Volcanoes of Great Britain. 



