MATERIALS OF THE EARTH 



13 



the stratified rocks of the land, like the recent sediments of the sea, 

 frequently contain the shells and skeletons of animals, and some- 

 times the impressions of plants. Most of the relics of life found 

 in the stratified rocks belonged to animals or plants which lived 



Fig. 2. Stratified rock. Trenton Limestone, Fort Snelling, Minn. (Calvin.) 



in salt water. Because of their structure, their composition, their 

 distinctive markings, and the remains of life which they contain, 

 it is confidently inferred that most of the stratified rocks which 

 lie beneath the mantle rock of the land were originally laid down 



Fig. 3. Diagrammatic representation of the relations of igneous rock to 

 stratified rock. The igneous rocks, represented in black, have been 

 forced up from beneath. 



in beds beneath the sea, and that the familiar processes of the present 

 time furnish the key to their origin. 



Igneous rocks m&y be loosely defined as hardened lavas. They 

 sustain various relations to the stratified rocks, as illustrated by 



