CHAP. III. CENTRAL DISTRICT OF SCOTLAND. 51 



one and that of the other. Such an association of these 

 canoes, therefore, cannot be regarded as j)roving synchronous 

 deposition ; nor, on the other hand, can we affirm any differ- 

 ence of age from mere relative position, unless we see one 

 canoe actually buried beneath another."* 



At the time when the ancient vessels, above described, 

 were navigating the waters where the city of Glasgow now 

 stands, the whole of the low lands which bordered the 

 present estuary of the Clyde formed the bed of a shallow 

 sea. The emergence appears to have taken place gradually 

 and by intermittent movements, for Mr. Buchanan describes 

 several nan-ow terraces one above the other on the site of 

 the city itself, with steep intervening slopes composed of 

 the laminated estuary formation. Each terrace and steep 

 slope probably mark pauses in the process of upheaval, 

 during which low cliffs were formed, with beaches at their 

 base. Five of the canoes were found within the precincts 

 of the city at different heights on or near such terraces. 



As to the date of the upheaval, the greater part of it 

 cannot be assigned to the stone period, but must have taken 

 place after tools of metal had come into use. 



Until lately, when attempts were made to estimate the 

 probable antiquity of such changes of level, it was confidently 

 assumed, as a safe starting-point, that no alteration had 

 occurred in the relative level of land and sea, in the central 

 district of Scotland, since the construction of the Roman or 

 Pictish wall (the " Wall of Antonine"), which reached from 

 the Firth of Forth to that of the Clyde. The two extremities, 

 it was said, of this ancient structure, bear such a relation to 

 the present level of the two estuaries, that neither subsidence 

 nor elevation of the land could have occurred for seventeen 

 centu.ries at least. 



But Mr. Geikie has lately shown that a depression of 



* Geikie, Geol. Quart. Journ. vol. xviii. p. 222. 1862. 



