278 SCIENCE PROGRESS. 



ranging in age from the Carboniferous to the Cretaceous 

 inclusive ; and that, as a consequence, we must refer the 

 production of the striking and very characteristic features of 

 those Highland districts to the last great epoch of the 

 earth's history — the Tertiary — and very largely, indeed, 

 to the latest portion of that epoch, namely the Pliocene "(2). 

 Of the three other areas, Wales, which is essentially 

 composed of Lower Palaeozoic rocks, possesses a drainage 

 radiating from the Plinlimmon district situated in a synclinal 

 fold of these rocks and accordingly can hardly owe its 

 present drainage directly to the Devonian uplifts, though 

 as Carboniferous rocks nearly surround it on three sides, it 

 might at first sight appear likely that the drainage system 

 was a Permian one ; in Devonshire the drainage is from 

 a watershed coinciding in the main with a synclinal axis 

 produced during the Permian uplift, and this would indicate 

 initiation of the present drainage after Permian times ; the 

 Pennine uplift is also largely Permian, but here the water- 

 shed coincides in the main with the dominant anticlinal 

 axis, and we might very well suppose, in the absence of 

 other evidence, that the Pennine rivers were initiated during 

 the Permian period of uplift. 



There is, however, other evidence, which suggests a 

 late date for the drainage of the Scotch, Welsh, Pennine 

 and Devon areas alike, and we may briefly glance at this. 

 Examination of a geological map of Europe will show 

 that the Mesozoic and Tertiary rocks of England occupy 

 the western end of a complex syncline, with an axis directed 

 in a general east and west direction, and the age of the 

 rocks included in this folded system indicates that their 

 uplift took place during the Micocene period of elevation. 

 But the mean trend of the Mesozoic rocks of Britain is 

 nearly north-east and south-west, for the strike approxi- 

 mates to a north and south direction in Linconshire and 

 South Yorkshire (the dip being east), whilst the strike is 

 practically east and west in the south of England. This 

 modification in the direction of strike is undoubtedly due 

 to the uplifts of the Mendip and Pennine systems, which 

 have the same general direction as the strike of the newer 



