334 THE rOSITION op the loess. chap. XVI. 



equivll}" available to account for the nature and geological 

 distribution of the loess. But we must suppose that the 

 amount of depression and re-elevation in the central region 

 was considerably in excess of that experienced in the lower 

 countries, or those nearer the sea, and that the rate of sub- 

 sidence in the latter was never so considerable as to cause 

 submergence, or the admission of the sea into the interior of 

 the continent by the valleys of the principal rivers. 



We have already assumed that the Alps were loftier than 

 now, when they were the source of those gigantic glaciers 

 which reached the flanks of the Jura. At that time gravel was 

 borne to the greatest distances from the central mountains 

 through the main valleys, Avliich had a somewhat steeper slope 

 than now, and the quantity of river-ice must at that time 

 have aided in the transportation of pebbles and boulders. 

 To this state of things gradually succeeded another of an 

 opposite character, when the fall of the rivers from the 

 mountains to the sea became less and less, while the Alps 

 were slowly sinking, and the first retreat of the great glaciers 

 was taking place. Suppose the depression to have been at 

 the rate of five feet in a century in the mountains, and only 

 as many inches in the same time nearer the coast, still, in 

 such areas as the eye could survey at once, comprising a 

 small part only of Switzerland or of the basin of the Ehine, 

 the movement might appear to be uniform, and the pi'e- 

 existing valleys and heights might seem to remain relatively 

 to each other as before. 



Such inequality in the rate of rising or sinking, M'hen we 

 contemplate large continental spaces, is quite consistent with 

 what we know of the course of nature in our own times, as 

 well as at remote geological epochs. Thus, in Sweden, as 

 before stated, the rise of land now in progress is nearly uni- 

 form, as we proceed from north to south, for moderate distances; 

 but it greatly diunnishes southwards if we compare areas 



