16 
AMERICA THE OLD WORLD. 
lesser periods are the separate reigns contained 
therein. Of such epochs there are ten, well 
known to geologists ; of the lesser periods about 
sixty are already distinguished, while many more 
loom up from the dim regions of the past, just 
discerned by the eye of science, though their his-' 
tory is not yet unravelled. 
Before proceeding further, I will enumerate 
the geological epochs in their succession, confin- 
ing myself, however, to such as are perfectly well 
established, without alluding to those of which 
the limits are less definitely determined, and 
which are still subject to doubts and discussions 
among geologists. As I do not propose to make 
here any treatise of Geology, but simply to place 
before my readers some pictures of the old world, 
with the animals and plants that have inhabited 
it at various times, I shall avoid, as far as pos- 
sible, all debatable ground, and confine myself to 
those parts of my subject which are best known, 
and can therefore be more clearly presented. 
First, we have the Azoic period, devoid of life , 
as its name signifies, — namely, the earliest strati- 
fied deposits upon the heated film forming the 
first solid surface of the earth, in which no trace 
of living thing has ever been found. Next comes 
the Silurian period, when the crust of the earth 
had thickened and cooled sufficiently to render 
the existence of animals and plants upon it pos- 
