CHAP. xvr. MUD PRODUCED BY GLACIERS. 325 



loess, a step the move necessary, as a French geologist, for 

 whose knowledge and judgment I have great respect, tells 

 me he has come to the conclusion that " the loess" is " a myth," 

 having no real existence in a geological sense, or as holding 

 a definite place in the chronological series. 



No doubt it is true that in every country, and at all 

 geological periods, rivers have been depositing fine loam on 

 their inundated plains in the manner explained above at 

 p. 34, where the Nile mud was spoken of. This mud of the 

 plains of Egypt, according to Professor Bischofl"s chemical 

 analysis, agrees closelj^ in composition with the loess of the 

 Rhine.* I have also shown (p. 201), when speaking of the 

 fossil man of Natchez, how identical in mineral character, and 

 in the genera of its terrestrial and amphibious shells, is the 

 ancient fluviatile loam of the MississipjM with the loess of the 

 Rhine. But granting that loam presenting the same aspect 

 has originated at different times and in distinct hydrogra- 

 phical basins, it is nevertheless true that, during the glacial 

 period, the Alps were a great centre of dispersion, not only of 

 erratics, as we have seen in the last chaj^ter, and of gi-avel, 

 which was carried flirther than the erratics, but also of very 

 fine mud, which was transported to still greater distances and 

 in greater volume down the principal river-courses between 

 the mountains and the sea. 



Mud ^produced by Glaciers. 

 They who have visited Switzerland are aware that every 

 torrent which issues from an icy cavern at the extremity of a 

 glacier is densely charged with an impalpable powder, pro- 

 duced by the grinding action to which the subjacent floor of 

 rock and the stones and sand frozen into the ice are exjiosed 

 in the manner before described. We may thei-efore readily 



* Chemical and Physical Geology, vol. i. p. 132. 



