MUSEUM OF COMPAKATIVE ZOOLOGY. 237 



A rough analysis yielded results as below. This indicates that the 

 rock is more nearly related to the andesites than trachytes, though 

 abnormally rich in potash. The rock vjas found to contain a notable 

 amount of free sodium chloride, derived presumably from ocean spray, 

 which may in part account for the high pei'centage of soda. 



99.44 

 Washington, D. C, October, 1892. 



