WATERSHED 135 



in raised beaches ; and to ice, as in the drift-covered 

 lowlands. 



The existing Watershed of Britain is profoundly sig- 

 nificant, affording a kind of epitome of the geological 

 revolutions, through which the surface of the country 

 has passed. It lies nearer the west than the east coast. 

 The western slope being thus the steeper, as well as 

 the more rainy, erosion must be greater on that side, 

 and consequently the watershed must be slowly moving 

 eastward. Probably the oldest part of the watershed is 

 to be found in the Highlands, where its trend from 

 north-north-east to south-south-west was determined 

 by the older Palaeozoic upheaval. Its continuity has 

 been interrupted by the dislocation of the Great Glen. 

 After quitting the Highlands it wanders across the 

 Scottish Lowlands and Southern Uplands, with no re- 

 gard to the dominant geological structure of these 

 districts, as if, when its course was originally de- 

 termined, they had been buried under so vast a mass 

 of superincumbent rock that their structure did not 

 affect the surface. Running down the Pennine Chain, 

 the watershed traverses a region of enormous erosion, 

 yet from its general coincidence with the line of 

 the axis of elevation, we may perhaps infer that 

 the anticline of the Pennine Chain has never been 

 lost under an overlying sheet of later undisturbed 

 rocks. The remarkable change in the character of the 

 watershed south of the Pennine Chain carries us back 

 to the time when the great plain of the Secondary rocks 

 of England was upraised with a gentle inclination to 

 east and south-east. The softer strata between the 

 harder escarpment-forming members of the Jurassic 



