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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 CaCOs, 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 

 CaCOs ranges from 93 to 97, where there is no undue concentration of MgCOs, 

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

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

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



* Analyses by L. G. Fairchild. 



* 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 CaCO.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. 



