eme tip of
Scotland, belong to the same age, it is believed that a continent, of
which they are fragments, united America and Europe across the North
Atlantic. Of the rest of what is now Europe there were merely large
islands--one on the border of England and Wales, others in France,
Spain, and Southern Germany. Asia was represented by a large area in
China and Siberia, and an island or islands on the site of India. Very
little of Africa or South America existed.

It will be seen at a glance that the physical story of the earth
from that time is a record of the emergence from the waters of larger
continents and the formation of lofty chains of mountains. Now this
world-old battle of land and sea has been waged with varying fortune
from age to age, and it has been one of the most important factors
in the development of life. We are just beginning to realise what a
wonderful light it throws on the upward advance of animals and plants.
No one in the scientific world to-day questions that, however imperfect
the record may be, there has been a continuous development of life from
the lowest level to the highest. But why there was advance at all, why
the primitive microbe climbs the scale of being, during millions
of years, until it reaches the stature of humanity, seems to many a
profound mystery. The solution of this mystery begins to break upon us
when we contemplate, in the geological record, the prolonged series of
changes in the face of the earth itself, and try to realise how these
changes must have impelled living things to fresh and higher adaptations
to their changing surroundings.

Imagine some early continent with its population of animals and plants.
Each bay, estuary, river, and lake, each forest and marsh and solid
plain, has its distinctive inhabitants. Imagine this continent slowly
sinking into the sea, until the advancing arms of the salt water meet
across it, mingling their diverse populations in a common world, making
the fresh-water lake brackish or salt, turning the dry land into swamp,
and flooding the forest. Or suppose, on the other hand, that the land
rises, the marsh is drained, the genial climate succeeded by an icy
cold, the luscious vegetation destroyed, the whole animal population
compelled to change its habits and its food. But this is no imaginary
picture. It is the actual story of the earth during millions of years,
and it is chiefly in the light of these vast and exacting changes in the
env