SALINITY OF OCEAN- WATER AT FOWEY ROCKS, FLORIDA. 



By Richard B. Dole and Alfred A. Chambers, 



Chemists, U. S. Geological Survey. 



Plate 99; text-figures 6, 7. 



The following study of the salinity of ocean water off the coast of Florida 

 was made at the request of Dr. T. W. Vaughan, of the U. S. Geological 

 Survey, in connection with his investigations of the deposition of limestone 

 along the Atlantic Coastal Plain, and the analytical results serve to amplify 

 the information gained by the world-wide study of the concentration of ocean 

 water that has been fostered by the Conseil permanent international de la 

 Mer. 



Fowey Rocks, on the eastern edge of the coral reefs bordering Biscayne 

 Bay (see plate 99), is the site of a lighthouse known as Fowey Rocks 

 Light. The light is 15 miles S. 25° E. of Miami, 6| miles S. 35° E. of Cape 

 Florida on Key Biscayne, about 4 miles east of the main series of reefs and 

 keys bordering Biscayne Bay, and about 12 miles east of the mainland. A 

 mile or two east of the light the floor of the ocean is 600 to 1,200 feet below 

 sea-level under the western margin of the Gulf Stream. According to obser- 

 vations of the U. S. Coast and Geodetic Survey the average current 8 miles 

 east of Fowey Rocks is 2.6 knots and 11.5 miles east is 3.6 knots an hour.^ 

 Consequently the salinity of the water in the vicinity of Fowey Rocks might 

 be expected to represent with fair accuracy that of the Gulf Stream shortly 

 after its emergence from the Gulf of Mexico. 



In accordance with instructions issued by Hon. George R. Putnam, Com- 

 missioner, U. S. Bureau of Lighthouses, daily samples, with some omissions, 

 were collected from Atlantic Ocean off Fowey Rocks, Florida, by the light- 

 keeper from March 24, 1914, to October 17, 191 5, under the direction of 

 Dr. H. F. Moore of the U. S. Bureau of Fisheries. The samples were col- 

 lected in 350 c.c. citrate of magnesia bottles about 18 inches below the 

 surface and were shipped for examination as opportunity afforded to the 

 laboratory at Washington, D. C. The chloride content of each sample was 

 determined by titration, and the salinity and specific gravity were calculated 

 from the result of this determination. These data, with the condition of the 

 tide, the direction and velocity of the wind, and the condition of the weather 

 as reported by the light-tender and the precipitation recorded at the station 

 of theU. S. Weather Bureau at Miami, Florida, are given in the accompanying 

 table. The determinations of chloride from March 12 to June 18, inclusive, 

 1914, were made by E. C. Bain; from June 19 to December 24, inclusive, 

 1914, by C. D. Parker; and from December 25, 1914, to October 17, 1915, 

 inclusive, by A. A. Chambers. The results were computed and tabulated by 

 Mr. Chambers. 



'U. S. Coast and Goedetic Survey Coast chart No. l66, Florida Reefs, from Key Biscayne to Carysfort Reef. 



299 



