ITS PROBABLE MARINE ORIGIN 41 



summits melted and added their glacial silt to these 

 mud-laden waters. 1 



On the uplift of the land portions of this sediment 

 would be swept away by the effluent waters, and de- 

 posited again on lower levels. Much would never- 

 theless be left at high levels, where the currents 

 were comparatively slow, while, as the waters fell 

 and became restricted to narrower channels, the 

 velocity of the currents, and consequently their 

 erosive power would increase. The denudation, 

 therefore, in the valleys would be considerable whilst 

 on the plateau lands it might be comparatively 

 slight. 



Large portions of the high-level Loess are un- 

 fossiliferous ; when organic remains are present they 

 are always those of a land surface. Land shells, and 

 the remains of the ordinary Quaternary Mammalia, 

 such as we have noted in the Head, and ossiferous 

 fissures are of occasional occurrence. In some few 

 instances human remains have been found. 2 



1 Argillaceous silt of this description falls with extreme slow- 

 ness in fresh water, whereas in salt water it is precipitated with 

 great rapidity. It has been found (Robertson, Trans. GeoL Soc. 

 Glasgow, vol. iv., p. 257) that in four hours a precipitate takes 

 place in salt water, which it takes days to effect in fresh water. 

 We can conceive, therefore, that after the submergence, the 

 turbid flood waters would quickly settle and throw down a 

 mantle of loam over the submerged land, especially in the 

 vicinity of the glacier centres. 



2 Until the division between the high-level and the fluviatile 

 Loess has been better defined, some uncertainty must exist as to 

 which of the two forms of Loess, some of the organic remains 

 hitherto found, are to be referred. 



