Rivers of Scotland. 527 



I know myself, but for fuller details the reader must 

 refer to Professor Geikie's work, from which part of 

 what I have to say is drawn. 



By referring to any good geological map of Scotland 

 and the north of England, it will be seen that the 

 country is intersected by two great valleys, running from 

 north-east to south-west, viz., the valley of Loch Ness 

 running from Moray Firth to Loch Linnhe, and also 

 the valleys of the Forth and Clyde. If we go farther 

 south another valley traverses England from Tyne- 

 mouth to the Sol way Firth. The general strike of all 

 the older formations of Scotland is more or less from 

 south-west to north-east, and starting from the watershed 

 of the north-west of Scotland between Loch Linnhe and 

 Cape Wrath, it will be seen that almost all the larger 

 rivers flow to the east and south-east, transverse to the 

 strike of the strata. In fact, like the Thames, they 

 may be said to start from a great scarped watershed 

 facing the Atlantic, and run from thence more or less 

 in accordance with the general dip of the strata, or 

 rather in conjunction with that, down a sloping plain 

 of marine denudation, till they find their way into the 

 sea or into the great valley of Loch Ness. Thus, in 

 some degree, they follow the same general law that 

 guided the east-flowing rivers of England, though 

 traversing much more mountainous ground, they have 

 cut their valleys in hard, greatly disturbed, and meta- 

 morphic Lower Silurian strata. 



South of the Great Valley, the rivers follow a north- 

 east course, in Strath Dearn and Strath Spey, approxi- 

 mately parallel to the trend of the Great Valley, 

 running in valleys probably excavated in lines of strike 

 occupied by strata, less hard than the general mass of 

 the country. The Tay does the same in the upper part 



