trivance expended
on their structures, and even on their external ornament, when there
was no intelligent mind on earth to appreciate their beauties. Even in
the present world we may as well ask why the uninhabited islands of
the ocean are found to be replete with luxuriant vegetable life, why
God causes it to rain in the desert where human foot never treads, or
why he clothes with a marvellous exuberance of beautiful animal and
plant forms the depths of the sea. We can but say that these things
seemed and seem good to the Creator, and may serve uses unknown to us;
and this is precisely what we must be content to say respecting the
plant-creation of the Eozoic period.

Some writers[89] on this subject have suggested that the cosmical use
of this plant-creation was the abstraction from the atmosphere of an
excess of carbonic acid unfavorable to the animal life subsequently to
be introduced. This use it may have served, and when its effects had
been gradually lost through metamorphism and decay, that second great
withdrawal of carbon which took place in the Carboniferous period may
have been rendered necessary. The reasons afforded by natural history
for supposing that plants preceded animals are thus stated by
Professor Dana:

"The proof from science of the existence of plants before animals is
inferential, and still may be deemed satisfactory. Distinct fossils
have not been found, all that ever existed in the azoic[90] rocks
having been obliterated. The arguments in the affirmative are as
follows:

"1. The existence of limestone rocks among the other beds, similar
limestones in later ages having been of organic origin; also the
occurrence of carbon in the shape of graphite, graphite being, in
known cases in rocks, a result of the alteration of the carbon of
plants.

"2. The fact that the cooling earth would have been fitted for
vegetable life for a long age before animals could have existed; the
principle being exemplified everywhere that the earth was occupied at
each period with the highest kinds of life the conditions allowed.

"3. The fact that vegetation subserved an important purpose in the
coal-period in ridding the atmosphere of carbonic acid for the
subsequent introduction of land animals, suggests a valid reason for
believing that the same great purpose, the true purpose of vegetation,
was effected through the ocean before the _waters_ were fitted for
animal life.

"4. Vegetation being directly or med