NORTH-CAKOLINA GEOLOGICAL SURVEY. 107 



Another specimen of consolidated marl from Benjamin 

 Biddle's plantation (Egypt) gave me : 



Sand, 9.60 



Peroxide of iron snd alumina, containing phosphoric 



acid, 4.40 



Carbonate of lime, 85.00 



Magnesia, trace, 



99.00 



A few grains of coarse sand were visible in the rock. This 

 mass is evidently sufficiently pure for burning into lime. It 

 would be adapted for the various purposes for which lime is 

 required, as mortar, whitewashing, or for agriculture. 



CHAPTER IX. 



FERTILIZERS CONTINUED. 



Shell marl. Heterogeneous in its composition, and arrangement of its 

 materials. Chemical constitution. Application of marl. Poisonous 

 marl. How corrected. Theories respecting the operation of marl. 



78. The third bed of marl in the ascending order has 

 been appropriately called shell marl, from the great abun^ 

 dance of undecomposed marine shells, of which it is mainly 

 composed. The mass, taken as a whole, is formed of per- 

 fect shells, and those which have become fragments, and 

 sand. There is no order in their arrangement in the bed. 

 They lie as if they had been washed up on a beach ; hence, 

 they are mixed confusedly together. The relative position of 

 the shell marl is exhibited in the sections already given. It 

 is not present, however, even where all the other members 

 of the sections in a bluff or outcrop exists. Whether its 



