Page:The Music of the Spheres.djvu/307

 The elevated sea-bottom is a fertile field for the fossil hunter, affording evidence that enables the geologist to reconstruct the evolutionary development of life on our planet in its divinely ordained stages. There is often but little resemblance in the fossils found in the lower strata to the plants and animals now in existence, but traced from stratum to stratum, the connection is obvious. The "fire-formed" rocks of the Archæan Age, which support all the other strata, contain no evidence of life; neither do the first sedimentary rocks which were deposited above them. The first fossils are found in the strata overlying the first sedimentary rock.

Geologists have divided the history of the earth into seven ages:

1. The Archæan Age, represented by the Archæan system of rocks.

2. The Age of Invertebrates, represented by the Cambrian, the Lower Silurian and the Upper Silurian rocks.

3. The Age of Fishes, represented by the Devonian rocks.

4. The Age of Amphibians, represented by the Carboniferous rocks.

5. The Age of Reptiles, represented by the Mesozoic rocks.

6. The Age of Mammals, represented by the Cenozoic rocks.

7. The Age of Man, represented by recent rocks.

All of these Ages, which represent the life history of the world, left their impression on the rocks of their times, and each Age is connected with the preceding and the succeeding Age like links in a long, long chain.

In regard to the distinctness and importance of the last great era, the Age of Man, Le Conte, in "Elements of Geology," says that there are two views which will ever divide geologists, depending on the two views regarding the relation of man to Nature:

"From a purely structural and animal point of view, man is very closely united with the animal kingdom. He has no department of his own, but belongs to the vertebrate department, along with the quadrupeds, birds, reptiles and fishes. He