But we also know that this period came to an end, and that once
more the ice descended. This is shown by the fact that directly
overlying the lignite beds are alternating layers of sand and
gravel, and, resting on these, glacier-born bowlders. The same
conclusion follows from the discoveries made at many
other places.

In Scotland it is well known that the bowlder clay contains
every now and then scattered patches of peat and beds of soil
either deposited in lakes or rivers. The only explanation that
can be given for their presence is that they represent old land
surfaces; that is, when the land was freed from ice, and
vegetation had again clothed it in a mantle of green. In this
cut is shown one of these beds. Both above and below are the
beds of bowlder clay. The peat in the centre varies from an inch
to a foot and a half in thickness, and contains many fragments
of wood, sticks, roots, etc.; and of animals, numerous beetles
were found, one kind of which frequents only places where deer
and ruminant animals abound.


Diagram of Interglacial Bed------------

From a large number of such discoveries it is conclusively shown
that, after all, Scotland was smothered under one enormous
glacier, a change of climate occurred, and the ice melted away.
Then Scotland enjoyed a climate capable of nourishing sufficient
vegetation to induce mammoths, Irish deer, horses, and great
oxen to occupy the land. But the upper bowlder clay no less
conclusively shows that once more the climate became cold, and