T. F. Jamieson — Oscillation of Land in Glacial Period. 461 



was at an end. If tlie direction of the movement was then reversed, 

 and, during the re-elevation of the continent, the inLind region 

 nearest the mountains shouhl rise more rapidly than that near the 

 coast, the river would acquire a denuding power sufficient to enable 

 it to sweep away gradually nearly all the loam and gravel with 

 which parts of its basin had been filled up." ^ 



Now. the Rhine and the Danube both take their rise in the Alps 

 and high mountains of Central Europe, and we know that daring the 

 formation of the Loess these mountains were deeply covered with 

 ice, which spread over Switzerland and the neighbouring regions. 

 We have, therefore, only to suppose that this ice depressed the 

 mountain tract on which it rested, and thus lessened the slope of the 

 npper vallej'^s of the Rhine and Danube, just as it did in the case of 

 the Mississippi. The consequence would be that these rivers would 

 no longer be able to hurry along gravel and pebbles as they did 

 before, but would have to slacken speed and expand into pools and 

 marshes, wherein the Loess would be deposited. Then, after the 

 ice melted, the mountain area would rise again, and set the rivers 

 aflowing down the valleys, and make them cut into the old beds of 

 silt just as Lyell describes. 



Judging from the accounts of Lyell, Belt, Daubree, and others, it 

 would seem that the valley of the Rhine had been excavated to more 

 than its present depth in times previous to the deposition of the 

 Loess, for it lies upon the top of strata of gravel which occupy the 

 bed of the river, and contain the remains of an older fauna. 



Mr. Archibald Geikie made a good suggestion in reference to the 

 Rhenish Loess. He supposed that the advance of the Scandinavian 

 glacier might have blocked up the mouth of the river and thus 

 dammed the water into a lake in which the Loess would then be 

 deposited. But this would not account for the Danubian Loess ; 

 moreover, the Loess does not seem to be exactly a lacustrine deposit, 

 for its surface does not form a horizontal line but slopes somewhat 

 down the valley, and the shells found in it do not, according to 

 Lyell, imply the permanent sojourn of a body of freshwater on the 

 spot, the most aquatic of them, the Succinea elongata, being an in- 

 habitant of marshes and wet grassy meadows. 



It seems likely that there might be not only a slight sinking of 

 the ice-covered tract, but likewise a tendency to bulge up in the 

 region which lay immediately beyond this area of depression ; just 

 as we sometimes see in the advance of a railway embankment, 

 which not only depresses the soil beneath it, but also causes the 

 ground to swell up ftirther off. The ice, therefore, by depressing 

 the upper pai't of the valleys and raising their mouths, would check 

 the flow of the rivers and lead to stagnation in the i-egion between, 

 where fine mud or loess would therefore accumulate. The material 

 of the loess may have been derived from the fine mud suspended in 

 the water flowing from the glaciers, or partly also, as suggested by 

 Baron Richthofen, from dust carried by the wind. 



1 Students' Elements of Geology, 2nd ed. p. 133. See also Lyell's Antiquity of 

 Man, chap. xvi. for fuller details regarding the Loess. 



