Some Chemical Characteristics of Sea-water at Tortugas. 75 



kilogram, is less than some of the differences, the variations are about what 

 might be expected in a series of examinations of a flowing water. 



The quantity of acid required to neutralize the cold sea-water in presence 

 of phenolphthalein proves conclusively that "free" carbon dioxide, in the 

 ordinary acceptance of that term in America, is not present. Consequently, 

 the inflowing waters at Tortugas would have no soluble action on deposits 

 of calcium carbonate by virtue of the carbon dioxide they contain. One- 

 half the carbon dioxide in equilibrium as the bicarbonate radicle (HCO3) 

 is commonly termed the "half-bound" carbon dioxide and that quantity is 

 probably the carbon dioxide referred to as "free" by some writers on the 

 composition of sea-water. So far as can be ascertained from the literature 

 the carbonate radicle (CO3), but not the free acid, is always present in sea- 

 water; or, as Dittmar expressed it in his computation of hypothetical com- 

 binations, the carbon dioxide is more than sufficient to complete the forma- 

 tion of the carbonate but considerably less than is required to form the 

 bicarbonate.^ Dittmar reports^ the average alkalinity of 130 samples of 

 ocean water as 54.70 milligrams per liter of CO2, meaning thereby the com- 

 bined carbon dioxide (total minus the half-bound acid) ; the corresponding 

 figure computed from the results at Tortugas is 52.5 milligrams per liter. 



Briefly, it may be stated that the condition and the quantity of carbon 

 dioxide in the water entering Tortugas Harbor do not appear to be essen- 

 tially different from those of the escaping water or normal sea-water. The 

 inflowing water has no apparent action on deposits of calcium carbonate by 

 virtue of its content of carbon dioxide. 



SEA-WATER AROUND BISCAYNE BAY. 

 HYDROGRAPHY. 



Biscayne Bay ranges from 3 to 8 miles in width and extends north and 

 south of the mouth of Miami River, though lying mostly south of it. It is 

 bounded on the east by low keys and reefs, through which there are numer- 

 ous narrow channels. It is very shallow, being for the greater part only 8 

 to 12 feet deep. Featherbed Bank, a shoal, cuts off the northern part of 

 the bay, and coral banks covered with sand extend from Ragged Keys to 

 Key Biscayne. Miami River is a small stream, discharging only about 400 

 second-feet at the time of sampling. 



COMPOSITION OF THE WATER OF MIAMI RIVER. 



No analyses of water from Miami River above tidal influence are avail- 

 able, but as it receives drainage from the Everglades its water is doubtless 

 similar in concentration and composition to that of Lake Okeechobee and 

 Fort Lauderdale Canal, analyses of which are quoted in Table i. These 

 are analyses of calcium-carbonate waters of low mineral content carrying 

 considerable organic matter. Normally Miami River may be expected to 

 contain a small amount of free carbon dioxide and no carbonate (CO3). 



» Quoted by Fox, C. J. J. Conseil permanent international de la mer, pub. de circonstance 44. Feb- 



« Dittmar, William. The alkalinity of ocean water. Report of the voyage of H. M. S. Challenger 

 1873-76, vol. I, p. 124. 



