and enormous changes of level. Such a great movement
unquestionably closed the Eozoic period of geology. Another of less
magnitude occurred in what is termed the Permian age at the end of the
Palaeozoic. A third terminated the Mesozoic age, and introduced the
Tertiary or Kainozoic. Perhaps we should reckon the glacial age,
though characterized by far less physical change than the others, as a
fourth. The possible physical causes which have been suggested for
such greater disturbances are the collapses of the crust in equatorial
regions, which may be supposed to have resulted at long intervals of
time, from the gradual retardation of the earth's rotation caused by
the tides, or the similar collapses and other changes due to the
shrinkages of the earth's interior caused by its gradual cooling, and
to the unequal deposition of material by water on different parts of
its surface.[67] The more full discussion of these points belongs,
however, to a future chapter.

These greater movements of the crust, would, as already stated,
coincide to some extent with the later creative days in the manner
indicated below:

==================================================================
Collapse of crust at close of | Close of Fourth AEon,
Eozoic Time, | and beginning of Fifth.
------------------------------------------------------------------
Collapse in Permian Period and | Middle of Fifth AEon.
end of Palaeozoic Time, |
------------------------------------------------------------------
Great subsidence and collapse | Close of Fifth AEon, and beginning
at close of Mesozoic Age, | of Sixth.
------------------------------------------------------------------
Great subsidence of the | End of Sixth AEon.
Pleistocene or Glacial Age, |
==================================================================

The question recurs--Why are God's days so long? He is not like us, a
being of yesterday. He is "from Olam to Olam," and even in human
history one day is with him as a thousand years; and we who live in
these later days of the world know full well how slow the march of his
plan has been even in human history. We shall know in the endless ages
of a future eternity that even to us these long creative days may at
last become but as watches in the night.

CHAPTER VII.

THE ATMOSPHERE.

"And God said, Let there be an expanse between the waters;