196 Flint Drift and Human Remains, 



conclusions which point to violent and sudden changes ; and, in' 

 the next place, it must be remembered that changes which in point 

 of geological time might well be accounted rapid, might never- 

 theless well occupy thousands of our years. There is proof in 

 these gravel beds of the Somme of a double motion, one of sub- 

 mergence to the depth of certainly more that 100 feet, another 

 of subsequent elevation, during which the immense mass of ma- 

 terial which had been brought down and deposited by water, has 

 been worn through and broken into escarpments, either by the 

 existing stream or by more powerful currents. We have no data 

 from which to measure in years the time which the accomplish- 

 ment of such a series of changes may imply. But I think the 

 general impression left upon the mind must be in favour of a very 

 high antiquity. Farther light may be cast upon this subject if the 

 drift-gravels of France, the south of England, and other countries 

 can be co-ordinated with any one of the stages of operation to 

 which we owe the superficial deposits of Scotland and the north of 

 Europe generally. It is well known that in these last there is one 

 prominent charactercstic which is absent farther south. I mean 

 the abundant proofs of glacial conditions, or an arctic climate. 

 On this subject there is a paper of great interest in the last 

 *' Quarterly Journal of the Geological Society," by Mr. Jamieson, 

 founded on observations made mainly in the county of Aberdeen. 

 The cycle of changes which this geologist thinks can be clearly 

 traced, as necessary to account for the superficial deposits of our 

 own country, amount to no less than five great epochs, including 

 two of submergence and two of elevation, and involving changes 

 of level to the extent of more than 2000 feet. Scotland hss long 

 ago furnished evidence as clear as that founded on the French 

 flint implements, that at least previous to the last of these eleva- 

 tions man had reached her shores, and navigated her rivers and 

 estuaries in those rude canoes, hollowed out of trunks of oak by 

 stone hatchets, which have been frequently found in elevated beds 

 of silt and gravel in the valley of the Clyde. And here we strike 

 upon evidence which has some bearing upon the question of time. 

 Closely connected with the period preceding the last elevation of 

 the land, we have proof that an arctic climate prevailed over a 

 large part of the northern hemisphere, whose climate is now com- 

 paratively temperate. But this period seems clearly to have been 

 one of long duration — that is to say, of such duration, and lasting 



