SALINITY OF OCEAN-WATER AT FOWEV ROCKS, FLORIDA. 



3" 



DILUTING EFFECT OF PRECIPITATION. 



The most apparent phenomenon that decreases the saUnity of the 

 water is precipitation, which dilutes the ocean-water to an uncertain depth. 

 The comparison of the precipitation recorded at the chmatological station 

 in Miami with the content of chloride of the water at Fowey Rocks, graphi- 

 cally represented in figure 5, shows that precipitation at Miami is almost 

 invariably followed within 24 hours by reduction of content of chloride at 

 Fowey Rocks. Some selected examples bring this out more clearly. The 

 average content of chloride for the period September 12, 1914, to October 

 17, 191 5, inclusive, is 19.87 grams per kilogram. Practically no precipita- 

 tion was recorded from October 27 to November 4, 1914, inclusive, and the 

 content of chloride ranged from 19.57 to 20.09 grams per kilogram. The 

 total precipitation from November 5 to 14, was 6.84 inches, the precipitation 



Clloride 



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*y\ 



(VV~^' 



IL^.|jlaLlJLl 



r^\ 



I I III I I I t 



r 



r 



^■'^ 



ill. .jJllLlJ 



t^. 



Jilliu 



Fig. S- — Graph showing daily content of chloride of sea-water at Fowey Rocks and daily precipitation at 

 Miami, Florida, September 12, 1914, to October 17, 1915. 



on November 8 having been 4.71 inches; the content of chloride fell from 

 20.00 grams on November 9 to 19.35 grams on November 10, where it 

 remained till November 16 during a period of practically no precipitation. 

 On the other hand, the total precipitation from November 14 to December 13, 

 inclusive, was only 0.36 inch and from November 16 to December 1 5, inclusive, 

 the chloride content ranged between 19.80 and 20.11, and averaged 20.00. 

 The quantitative effect of precipitation on the content of chloride is 

 not entirely regular, for it is complicated by the effects of tide, wind, 

 and current. For example, the total precipitation of 2.87 inches during 

 December 14 to 18, inclusive, 1914, was accompanied by a reduction of 

 chloride from 20.02 grams on December 15 to 19.01 grams during December 

 r8 to 22, inclusive. A precipitation of 1.96 inches on February 16, 1915, 

 however, was followed by a reduction of chloride from 20.03 oi^ February 

 15 to 19.93 on February 18. The precipitation from July 20 to 31, inclusive, 

 was 6.25 inches, and this was followed by a reduction of the content of 



