372 DANISH PEAT AND " KITCnEN-MIDDENS." chap. xix. 



vegetation. The pine, or Scotch fir, buried in the oldest 

 peat, gave place at length to the oak. and the oak, after 

 flourishing for ages, yielded, in its turn, to the beech, the 

 periods when these three forest-trees predominated in suc- 

 cession tallying pretty nearly with the ages of stone, bronze, 

 and iron in Denmark (p. 16). In the same country, also, 

 during the stone period, various fluctuations, as we have 

 seen, occurred in physical geography. Thus, on the ocean 

 side of certain islands, the old refuse-heaps, or "kitchen- 

 middens," were destroyed by the waves, the cliffs having 

 wasted away, while, on the side of the Baltic, where the sea 

 was making no encroachment, or where the land was some- 

 times gaining on the sea, such mounds remained uninjured. 

 It was also shown that the oyster, which supplied food to 

 the primitive people, attained its full size in parts of the 

 Baltic where it cannot now exist, owing to a Avant of saltness 

 in the water, and that certain marine univalves and bivalves, 

 such as the common periwinkle, mussel, and cockle^ of which 

 the cast-away shells are found in the mounds, attained in the 

 olden time their full dimensions, like the oysters, whereas 

 the same species, though they still live on the coast of the 

 inland sea adjoining the mounds, are dwarfed, and never half 

 their natural size, the water being rendered too fresh for them 

 by the influx of so many rivers. 



As for several calculations in which certain archaeologists 

 and geologists of merit have indulged, in the hope of arriving 

 at some positive dates, or exact estimates of the minimum of 

 time required for the changes in jihysical geogTaphy, or in 

 the range and numerical preponderance of certain species of 

 animals, or the advance in human civilization in the Eecent 

 Period or during the ages of stone, bronze, and iron, 

 whether the computation related to the growth of peat, or 

 to the conversion of Avater into land, since some lake-settle- 

 ments were founded, or the various dcj^tths at which, in the 



