46 EARLY MAN IN BRITAIN. [CHAP. in. 



extent and elevation. The granites of Arran, and, in 

 Ireland, those of the Mourne mountains and the basalts 

 of Antrim, are also referred to the same age. Thus, in 

 the Meiocene age, along a line of 400 miles from north 

 to south in the British area, there rose a chain of lofty 

 and active volcanoes, on a scale comparable to those of 

 the Andes, overwhelming from time to time with their 

 lava and ashes the Meiocene forests in their vicinity. 

 This line of ancient volcanoes is continued northwards 

 into the Faroes, Iceland, and Greenland. 



Denudation since the Meiocene Age. 



The present state of these volcanoes affords us a 

 means of measuring the destruction of rock in the post 

 Meiocene times. In Fig. 7 the dotted line represents 

 the outline of the Meiocene surface, while the actual 

 surface is shown by the continuous line. Not only 

 have their cones disappeared by the action of the ele- 

 ments, but the more solid accumulations forming their 

 bases have been reduced to mere fragments during the 

 untold ages which have passed away since they were 

 active. Since they have lost more than one half of 

 their former height, it is reasonable to suppose that 

 similar amounts of rock have been removed from other 

 areas in Great Britain, the greatest destruction being 

 wrought on the flanks of the mountains, and the least 

 on the slopes near the sea level. Under these circum- 

 stances, we could not expect that any traces of the 

 old Meiocene land surface or river deposits should be 

 preserved to the present day, excepting under very un- 

 usual conditions. They for the most part have been 

 swept away, along with a flora and fauna probably 



