the planet. This was the beginning of what we call life,
those little temporary gatherings of the earth's substance which take
shape in the form of animals and plants. As yet we do not know, we are
not likely indeed ever to know, just when or how this change from the
earlier stage in which the earth knew no living creatures to that in
which they were to abound in seas and on land. All that has been found
out concerning the matter leads us to believe that the first steps led
to the creation of very simple species--jellylike forms having but few
of the qualities which we commonly associate with living beings. But the
first steps taken in the immemorable ages, the others followed in quick
succession, so that the earliest fossil remains which we find in rocks
formed on the sea-bottom, a hundred million or more years ago, show that
the earth was richly peopled with a lowly life.

Probably at some time after the lands had risen above the sea, and had
begun to yield their waste in the form of mud, sand, and pebbles, to
provide strata on the sea-bottoms, volcanoes began to break forth on the
sea-bottom and along the margins of the continents. These strange
outbursts, mainly of steam, but often accompanied by molten rock, appear
to owe their formation to the accumulation of beds on the bottom of the
ocean, which as they are formed are to a great extent filled with water.
Accumulated to a thickness of many miles, the water in the lower part of
these strata gradually becomes exceedingly heated. In the end it breaks
forth in steam, having a temperature quite as hot as molten iron, so
that it may melt ordinary rocks.

The beginning of volcanic action on the earth was in a way important,
though the event is less noteworthy than any of those which have been
previously remarked, for tremendous as a volcanic eruption may be (that
of Kratakoa in 1883 shook a large part of the earth's surface, perturbed
all its atmosphere, and sent its dust to every part of the world), they,
after all, are not leading features in the earth's history, but rather
incidents. It is otherwise with the last great physical event in the
history of the earth, which we shall now have to consider.

As the earth became divided, so that there were a number of continents
and oceans, its climate became diversified. This was in part
accomplished by the changes in the course of the ocean currents, such as
our Gulf Stream; in part it may have been by slight variation in