NORTH-CAROLINA GEOLOGICAL SURVEY. 



Magnesia, 13.600 



Potash, 1.431 



Soda, 2.12S 



Organic matter, 1.600 



Water, 1.800 



100.614 



The sand is frequently in quite large angular grains. That 

 part of the bed which is green, or properly green sand, is not 

 so distinct as in New Jersey, and it would be impossible to 

 separate the grains mechanically, while in New Jersey they 

 may be separated from the other materials. These grains 

 have been analyzed by Prof. Cook, who has found them com- 

 posed of 



Silica, 45.510 



Protoxide of iron, 21.134 



Alumina, 7.960 



Magnesia, 2.400 



Potash, 6.748 



Lime, 3.842 



Phosphoric acid, 0.990 



Sulphuric acid, 1.129 



Carbonic acid, 0.563 



Sand, 0.850 



Water, 9.110 



100.209 



It has been found that the green grains in the green sand 

 possess a very uniform composition, and that taking the aver- 

 age analysis of several specimens the grains contain silica, 

 protoxide of iron, alumina, magnesia, potash and water in 

 nearly equal proportions, while the other constituents are 

 variable. The absence of the green grains in the marl of 

 black rock may account for the small percentage of potash 

 which is the principal element relied upon in the New Jer- 

 sey marl. The lime and magnesia of the Blackrock marl is 

 much greater than any of the New Jersey beds, and the sand 

 and silica are not in great excess. It really has as much fertil- 

 izing matte'r as the New Jersey marl, but it is deficient in the 

 most valuable part, potash. This element, however, seems 



