certain part of the sea becomes more salty than it has been before (or
less, for that matter) myriads of little fishes swim hastily to another
part of the wide ocean. As for the birds, a great many of them move from
one place to another regularly once a year. When the cold weather sets
in, the geese depart, and when the first swallow returns, we know that
summer is about to smile upon us.

Man is no exception to this rule. He likes the warm stove much better
than the cold wind. Whenever he has the choice between a good dinner and
a crust of bread, he prefers the dinner. He will live in the desert or
in the snow of the arctic zone if it is absolutely necessary. But offer
him a more agreeable place of residence and he will accept without a
moment's hesitation. This desire to improve his condition, which really
means a desire to make life more comfortable and less wearisome, has
been a very good thing for the progress of the world.

It has driven the white people of Europe to the ends of the earth.

It has populated the mountains and the plains of our own country.

It has made many millions of men travel ceaselessly from east to west
and from south to north until they have found the climate and the living
conditions which suit them best.

In the western part of Asia this instinct which compels living beings to
seek the greatest amount of comfort possible with the smallest
expenditure of labor forced both the inhabitants of the cold and
inhospitable mountains and the people of the parched desert to look for
a new dwelling place in the happy valley of Mesopotamia.