er animals, showing strong beginnings of
representative art. Also, in these caves were found bones and stone
implements of a more highly finished product than those of the earlier
primitive types of Europe.

_Shell Mounds_ (2).--Shell mounds of Europe and America furnish
definite records of man's life. The shell mounds of greatest historic
importance are found along the shores of the Baltic in Denmark. Here
are remains of a primitive people whose diet seems to be principally
shell-fish obtained from the shores of the sea. Around their kitchens
the shells of mussels, scallops, and oysters were piled in heaps, and
in these shell mounds, or Kitchenmiddens, as they are called
(Kjokkenmoddings), are found implements, the bones of birds and
mammals, as well as the remains of plants. Also, by digging to the
bottom of these mounds specimens of pottery are found, showing that the
civilization belonged largely to the Neolithic period of man.

There are evidences also of the succession of the varieties of trees
corresponding to the evidences found in the peat bogs, the oak
following the fir, which in turn gave way to the beech. These refuse
heaps are usually in ridgelike mounds, sometimes hundreds of yards in
length. The weight of the millions of shells and other refuse
undoubtedly pressed the shells down into the soft earth and still the
mound enlarged, the habitation being changed or raised higher, rather
than to take the trouble to clear away the shells from the habitation.
The variety of implements and the degrees of culture which they exhibit
give evidence that men lived a long time in this particular locality.
Undoubtedly it was the food quest that caused people to assemble here.
The evidences of the coarse, dark pottery, the stone axes, clubs, and
arrow-heads, and the bones of dogs show a state of civilization in
which differentiation of life existed. Shell mounds are also found
along the {74} Pacific coast, showing the life of Indians from the time
when they first began to use shell-fish for food. In these mounds
implements showing the relative stages of development have been found.

_River and Glacial Drift_ (3).--The action of glaciers and glacial
rivers and lakes has through erosion changed the surface of the soil,
tearing out some parts of the earth's surface and depositing the soil
elsewhere. These river floods carried out bones of man and the
implements in use, and deposited them, together with the bones