POSTGLACIAL, &c, DEPOSITS OP CONTINENT. 477 



In the summer of 1854 dredging operations in the bed of the 

 river Elbe, near Blankenese, brought up great quantities of 

 wood, pieces of amber, and freshwater -shells. The wood was 

 chiefly oak, which was black in colour and approached in 

 character to lignite. 1 



That a large part of Holland lies actually below the sea-level 

 is rendered sufficiently evident by the presence of the great 

 dikes which are maintained at such cost and trouble. Some 

 writers maintain that, this depression has resulted from the 

 gradual compression of the bogs and soils of the country, which 

 has followed the introduction of the general system of canal- 

 drainage. However this may be, the evidence supplied by 

 borings and by the superficial strata exposed to view in some 

 of the canals, renders it certain that Holland has experienced 

 a degree of submergence in postglacial times which cannot be 

 attributed to a mere lowering of surface consequent upon the con- 

 solidation of bogs and their associated deposits. Tetens, writing 

 in 1778, tells us that from Schleswig to the mouth of the Scheldt 

 peat occurs more or less deeply buried underneath recent marine 

 accumulations. 2 These deeply buried peat-beds are known as 

 Dargschichten, in East Friesland, where they occur at a depth of 

 from 10 or 12 feet to as much as 40 feet and more below the 

 present sea-level. They are frequently interbedded with marine 

 clays, as in the following section from the Warfen : — 3 



2 Reisen in die Marschliinder an der Nordsce, Bd. i. p. 172. 



3 For these details, see Arends : Physische Geschichte, Bd. i. pp. 84, 149, 231 ; 

 the same author's Ostfriesland und Jenver, Bd. i. p. 22 ; and Dr. Grisehach's 

 Ueber die Bildung des Torfs in den Emsmooren, p. 83, to which work I am under 

 special obligations for references to these and other sources of information. 



4 This is the term applied in Westphalia and Holland to the sand and gravel 



