ESTUARINE. 255 



earlier Celts hundreds of shallow lakes and morasses have 

 been converted into dry land ; and the process still goes 

 forward, accelerated in all civilised countries by the inces- 

 sant operations of man. 



Still associated with river-action, but necessarily separated 

 from strictly fluviatile deposits, are those Estuarine forma- 

 tions which occupy extensive areas in almost every region 

 of the globe. Wherever a river discharges itself into the 

 sea by a broad mouth, or by many mouths, and in particular 

 where the tidal influence pounds back the river- water and 

 runs for some distance inland, sandbanks and mud-shoals 

 have a tendency to accumulate. In process of time the 

 banks and shoals become islands, and by further accretion 

 and union the islands are converted into deltas. In this 

 way most of our larger rivers present deltic flats or estua- 

 rine formations, and these must have been slowly accumu- 

 lating since sea and land received their present relative 

 configurations. These accumulations, consisting mainly of 

 debris borne down by the river, but partly also of tidal 

 sediments, will imbed marine as well as terrestrial and 



other European countries, and point to a time when the early inhabitants 

 "betook themselves to this style of habitation for purposes of defence and 

 protection. In some instances, as in the Swiss lakes, the piled area is 

 of considerable extent (forming an aquatic village, as it were), and con- 

 nected with the shore by a piled way or causeway. In the older pfahl- 

 bauten the implements are chiefly of stone, and associated with the cast- 

 away bones of the deer, boar, and wild-ox ; in those of intermediate age, 

 bronze implements prevail, associated with the bones of the domestic ox, 

 pig, and goat ; while in the more recent, iron swords and spears have 

 been found, accompanied by carbonised grains of wheat and barley, and 

 with fragments of rude textures woven of flax, bast, and straw. The 

 more recent seem to have been immediately anterior to the great Roman 

 invasion of northern Europe ; the more ancient may be several thousand 

 years older than that event. Those curious in these matters may consult 

 Dr Keller's ' Lake-Dwellings of Switzerland,' as translated and arranged 

 by Mr Lee, 1866. 



