The age of stone in Denmark coincided with the period of the first
vegetation, or that of the Scotch fir, and in part at least with
the second vegetation, or that of the oak. But a considerable
portion of the oak epoch coincided with "the age of bronze," for
swords and shields of that metal, now in the Museum of Copenhagen,
have been taken out of peat in which oaks abound. The age of iron
corresponded more nearly with that of the beech tree.* (* Morlot
"Bulletin de la Societe Vaudoise des Sci. Nat." tome 6 page 292.)
[Note 4.]

M. Morlot, to whom we are indebted for a masterly sketch of the
recent progress of this new line of research, followed up with so
much success in Scandinavia and Switzerland, observes that the
introduction of the first tools made of bronze among a people
previously ignorant of the use of metals, implies a great advance
in the arts, for bronze is an alloy of about nine parts of copper
and one of tin; and although the former metal, copper, is by no
means rare, and is occasionally found pure or in a native state,
tin is not only scarce but never occurs native. To detect the
existence of this metal in its ore, then to disengage it from the
matrix, and finally, after blending it in due proportion with
copper, to cast the fused mixture in a mould, allowing time for it
to acquire hardness by slow cooling, all this bespeaks no small
sagacity and skilful manipulation. Accordingly, the pottery found
associated with weapons of bronze is of a more ornamental and
tasteful style than any which belongs to the age of stone. Some of
the moulds in which the bronze instruments were cast, and "tags,"
as they are called, of bronze, which are formed in the hole through
which the fused metal was poured, have been found. The number and
variety of objects belonging to the age of bronze indicates its