1 1 6 Physical Geography. 



this area was originally united to that which borders 

 the Firths of Moray and Dornoch, and from thence on 

 to the sandstones of Caithness and the Orkneys, I 

 cannot tell, though it has been usually stated that 

 the eastern side of the Lower Silurian rocks and the 

 Grampian heights were continuously fringed by Old 

 Bed Sandstone. It seems to me, however, to be not 

 unlikely, that as the great Grampian range south of 

 the Dee even now attains to heights of about 2,000 

 feet in Kincardineshire, in older times, having suffered 

 much less from denudation, they were higher than 

 now, stretched further east, and possibly formed an 

 effectual barrier between two lake-areas in which Old 

 Eed Sandstone was deposited. But even if the red 

 sandstones of the whole of Scotland were once united to 

 those of the coast of Norway, in one continuous stretch 

 of inland water, it is not without parallel in the 

 living world, for the brackish Caspian lake occupies 

 a larger area, and it has been said that even in his- 

 torical times the Caspian was larger than now. The 

 great fresh-water lakes also of North America, from 

 Lake Superior to Lake Erie, exclusive of Ontario, oc- 

 cupy an area far larger than the whole of Scotland with 

 all its islands. Three of these lakes, Superior, Michi- 

 gan, and Huron, practically form one sheet of water, 

 united by straits somewhat analogous to those of the 

 Bosphorus and Hellespont ; and the lowest of these, 

 Lake Huron, is only 37 feet below the level of Lake 

 Superior, while Erie is 36 feet lower than Lake Huron, 

 with a distance of more than 70 miles between them, 

 part of which is occupied by Lake St. Clair. 



When we try to realise the kind of scenery of this 

 old period, we are led to something of this kind. The 

 lake or lakes, was or were, more or less encircled by high 



