ever been in historical times, a native of the Danish Islands, and
when introduced there has not thriven; yet it was evidently
indigenous in the human period, for Steenstrup has taken out with
his own hands a flint instrument from below a buried trunk of one
of these pines. It appears clear that the same Scotch fir was
afterwards supplanted by the sessile variety of the common oak, of
which many prostrate trunks occur in the peat at higher levels than
the pines; and still higher the pedunculated variety of the same
oak (Quercus robur, L.) occurs with the alder, birch (Betula
verrucosa, Ehrh.), and hazel. The oak has now in its turn been
almost superseded in Denmark by the common beech. Other trees, such
as the white birch (Betula alba), characterise the lower part of
the bogs, and disappear from the higher; while others again, like
the aspen (Populus tremula), occur at all levels, and still
flourish in Denmark. All the land and freshwater shells, and all
the mammalia as well as the plants, whose remains occur buried in
the Danish peat, are of Recent species. [Note 3.]

It has been stated, that a stone implement was found under a buried
Scotch fir at a great depth in the peat. By collecting and studying
a vast variety of such implements, and other articles of human
workmanship preserved in peat and in sand-dunes on the coast, as
also in certain shell-mounds of the aborigines presently to be
described, the Danish and Swedish antiquaries and naturalists, MM.
Nilsson, Steenstrup, Forchhammer, Thomsen, Worsaae, and others,
have succeeded in establishing a chronological succession of
periods, which they have called the ages of stone, of bronze, and
of iron, named from the materials which have each in their turn
served for the fabrication of implements.