CHAPTER III. 
FOSSILS. 
WHAT ARE FOSSILS'? — WHAT DO THEY TEACH ? — PRESER- 
VATION OF FOSSILS — EVIDENCES OF LIFE IN AGES THAT 
ARE GONE — EVIDENCES OF THE MARINE OR FRESH- 
WATER ORIGIN OF ROCKS. 
A fossil may be described as the remains, or the 
traces of the remains, of any animal or plant which 
has been entombed in rocks. Each successive formation 
in the long history of the earth is characterized by 
fossils peculiar to itself. Dr. Page says shells, fishes, 
and other animals, are buried in the mud or silt of 
lakes and estuaries ; rivers also carry down the carcases 
of land animals, the trunks of trees and other vege- 
table drift ; and earthquakes submerge plains and 
islands, with all their vegetable and animal inhabitants. 
These remains become enveloped in the layers of mud 
and sand and gravel formed by the waters, and in 
process of time are petrified, that is, are converted into 
stony matter, like the shells and bones found in the 
oldest strata. Now, as at present, so in all former time, 
must the remains of plants and animals have been 
similarly preserved, and, as one tribe of plant is 
