4 6 



Tin: STORY OF THE EARTH. 



The limestones named oolites, are probably all 

 formed in moderate depth of water; since there is 



Fig. 6. Lithographic UmCStOne from Solrnhofen, showing circular 

 staining at the interM-ction of rectangular joints ; and corru- 

 gated fracture OO tin- ii^ r ht side. 



some evidence to show that the oolitic grains may 



be derived from plants like the Nullipores, and 



ns, termed Pisolite, show a minute 



tubular structure, attributed to an organism 



named ( iirvanclla. 



Beds of shell limestone are seen in process of 

 formation On many shores. Shell-haven, in the 

 Thames, takes its name fr >in the manner in 



winch shells are dritted together so as to form a 



deposit; and a similar accumulation may be ob- 



