THE GLACIAL PERIOD. 



237 



no space for the accumulation of silt. The muddy waters carried 

 down vast quantities of gravel and shingle, but the finer materials 

 were swept right out to sea. It will of course be understood 

 that in all the river- valleys of Central Europe enormous sheets 

 of gravel and shingle were swept along the bottoms of the 

 valleys, the loss only accumulating in places where the inundat- 

 ing waters were comparatively tranquil. 



The occasional occurrence in the loss of sporadic stones and 

 boulders, which are sometimes striated, points to transportation 

 by river-ice ; and the presence of lines of gravel and sand, which 

 here and there have been observed, indicate unquestionably the 

 action of water ; and the same may be said of such alternations 

 as those described by Dr. Nehring which occur at Thiede and 

 Westeregeln, and of the bedded loss of Heiligenstadt, near 

 Vienna, referred to by Dr. Jentzsch. Again, at Nussdorf and 

 Hungelbrunn, in the same region, the loss, according to Th. 

 Fuchs, contains freshwater-shells in a distinct bed ; at Nuss- 

 dorf the bed was a bluish-green silt with Hypnv.m, while at 

 Hungelbrunn it was a white marly deposit. Such instances of 

 stratification, however, are not common in the loss, which, like 

 the flood-deposits (mud and silt) of rivers such as the Mississippi 

 and the Ganges, generally shows little or no trace of bedding. 

 The calcareous concretions of the loss also find their counterparts 

 in the recent alluvia of the same rivers. The origin of the 

 vertical capillary structure is less easily accounted for. Some 

 writers believe that the minute tubes represent grasses and other 

 plants which were gradually buried as the loss accumulated 

 about them. But I am not aware that any trace of vegetable 

 matter has ever been found in the tubes, and the capillary 

 structure, like the concretions, may be of inorganic origin. 

 Chemical analyses, at all events, have shown that loss contains 

 little or no organic matter, which we might have expected to 

 meet with in much greater abundance had plants given origin 

 to the innumerable vertical pores which are so commonly pre- 

 sent in the typical deposit of the Rhine and the Danube. 



The character of the shells and other organic remains found 



