CHAPTER II. 

 SOURCES OF MATERIALS. 



In the preceding chapter the reader's at- 

 tention was centered on a few type speci- 

 mens of the shell forms found in stone quar- 

 ries. It is now proposed to dwell on the 

 materials of the enclosing rocks in explana- 

 tion of their structure and history. In order 

 to do this more fully, the thought of the 

 stone quarry must enlarge itself into the 

 wider thought of the whole rocky layer of 

 which this stone quarry is but a small frag- 

 ment. In short we are to think of a sea or 

 lake beach hundreds of miles in length strewn 

 with shells' and bones, often with leaves, fruits 

 and branches of trees, all buried in sand or 

 mud and elevated to the crests and slopes of 

 the hills and changed to solid rock. It is 

 with this wider group of facts we are now 

 concerned, and we propose to inquire about 



