SOUTHERN SCOTLAND. 305 



which terminates to the south of Edinburgh, is one of these groups of eruptive 

 rocks. 



The plain of the Forth and Clyde is traversed by a canal whose summit level 

 lies at an elevation of only 157 feet, and at this spot the separation between the 

 Lowlands and the mountain region of !N^orthern Scotland is consequently well 

 marked. But higher up, in Strathclyde, there exists another breach in the 

 mountains, for the Clyde, which now flows to the westward, formerly pursued its 

 course to the east, into the valley of the Tweed, and if measures were not taken to 

 protect against erosion the gravel deposits of the plain of Biggar, to the south of 

 Lanark, the Clyde would resume its ancient course.* The water-parting between 

 the Clyde and the Forth was formerly less elevated, for raised beaches are met 

 with at many places along the estuaries of the two rivers, at an elevation of 

 between 20 and 40 feet above the sea -level, and they contain the shells of 

 animals similar to those still living in the neighbouring seas. In the vicinitv 

 of Glasgow, where repeated opportunities for examining the soil are afforded 

 by the construction of sewers, the bones of whales, seals, and porpoises have 

 frequently been found at 20 or 30 feet above the actual level of the sea. At 

 the time these cetaceans were stranded man already lived in the countr}^ for 

 close to their bones boats of various descriptions have been discovered, some 

 of them mere dug-outs, such as are used by savages, but others skilfully con- 

 structed of planks, with pointed prows and square sterns. Mr. A. Geikie is of 

 opinion that these boats belong to the historical epoch, and that the Roman 

 conquerors of the country may have seen them afloat on the estuary of the 

 Clyde. In the bog of Blair Drummond, near the Firth of Forth, a whale was 

 unearthed, which had been harpooned by means of an instrument made of the 

 antlers of a stag.f In the neighbourhood of Falkirk, near the western extremity 

 of the Firth of Forth, the sea formerly extended up the river Carron, far bej'ond 

 the present head of the tide. The great Roman wall, named after Antoninus, 

 though begun by Agricola, extended from sea to sea, so as not to leave wide 

 passages at either end open to an invader. Yet no remains of this wall have 

 been found to the west of Dunglass, where it finishes at a height of 25 feet above 

 the present level of the sea. In the east it terminates on the top of a clifl", at 

 Carriden, near Falkirk.+ In the interior of the country the remains of this wall 

 may still be seen in a few places, and at the close of last century it was even 

 possible to distinguish ten forts and bridge-heads which defended the principal 

 river passages, and also portions of a ditch, 42 feet wide and 22 feet deep, which 

 extended along its northern face. This region, formerly of such strategical 

 importance, has, owing to its vicinity to two seas, its small elevation, and the 

 riches of its soil and subsoil, become one of the most prosperous of Great Britain, 

 and, indeed, of the whole world. Edinburgh and Glasgow are the two sentinels 

 of this Scotch isthmus. It was the action of the glaciers which destroyed the 



* A. Geikie, "Scenery and Geology of Scotland." 



t Ramsay, "Physical Geology and Geography of Great Britain." 



X Wilson, " Prehistoric Annals of Scotland ; " Eobert Chambers, " Ancient Sea Margins." 



129 



