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CARNEGIE INSTITUTION OF WASHINGTON. 



latitude of the north end of the Bahamas, off the Bahamas, across the Carib- 

 bean Sea from Jamaica to Panama, and off the southwest coast of Central 

 America to off the southern end of Lower California. These samples show a 

 gradual decrease in the percentage of CaC0 3 , and inversely an increase in the 

 percentage of material in a colloidal state from the shores of the Bahamas to 

 the deep sea. In the shallow-water samples in the Bahamas the percentage of 

 CaC0 3 ranges from 93 to 97, where there is no undue concentration of MgC0 3 , 

 and in the Tongue of the Ocean at depths of 800 to 825 fathoms there is 

 between 95 and 96 per cent CaC0 3 . The following are the percentages of 

 CaC0 3 and colloidal material in deep-sea samples from off the Bahamas: 



1 Analyses by L. G. Fairchild. 



2 Determination by U. S. Bureau of Soils. Method used, absorption of water-vapor. 



From the data at present available, the inference seems warranted that a 

 very high percentage of CaC0 3 in a limestone indicates a shallow-water or 

 only a moderately deep-water deposit. Such relations as those stated above 

 illustrate the nature of the results from a comparison of the Bahamian and 

 Floridian bottom deposits with marine deposits formed under other conditions. 



