PALEOZOIC CORAL REEFS 243 



Na 30.593 



K 1.106 



Rb 



Ca 1 . 197 



Mg 3.725 



Fe, SiOa, PO4 



Fe, NH4, NO3. 



AljOs, FegOs, SiOz 



100.000 



"... allowing for all possible sources of divergence, the essential uni- 

 formity in composition of ocean salts is perfectly clear. The mass of the 

 ocean is so great, and the commingling of its waters by winds and currents is 

 so thorough, that the local changes produced by the influx of rivers are ex- 

 ceedingly small. The salinity may range from less than 1 to over 4 per cent, 

 but the saline composition remains practically the same." 



SPECIFIC GRAVITY OF THE WATER 



The following data have been compiled from the Challenger reports : 



Localities. Range in specific gravity at 15° 56 C. 



Atlantic Ocean: 



Bermuda to Azores 1 .02686 to 1 .02715 



Cape Verde Islands to Saint Paul Rocks 1.02589 to 1 .02706 



Saint Paul Rocks to Fernando Noronha 1.02667 to 1 .02699 



Fernando Noronha to Bahia 1 .02628 to 1 .02748 



Pacific Ocean: 



Tongatabu to Fiji Islands 1.02640 to 1 .02659 



Fiji Islands to Cape York, Australia 1.02609 to 1.02672 



Meangis Islands to Admiralty Islands 1 .02405 to 1 .02576 



Meangis Islands to Japan 1.02564 to 1 .02570 



Admiralty Islands to Japan 1.02571 to 1.02580 



Sandwich Islands to Tahiti 1 . 02587 to 1 . 02696 



Tahiti to Valparaiso 1.02714 to 1 .02519 



The total range is from 1.02405 to 1.02748, or .003. 



To summarize the data on conditions under which modern coral reefs 

 are formed: (a) depth, maximum, 25 fathoms, light strong; (h) tempera- 

 ture, annual minimum, 68 degrees Fahrenheit; annual mean, above 

 70 degrees Fahrenheit; (c) ivater, agitated and circulating; (d) bottom , 

 firm or rocky, without silty deposits; (e) composition of the oceanic 

 salts, as for the oceanic waters as a whole; (f) specific gravity, as for 

 the ocean in general, range 1.02405 to 1.02748. Of these conditions 

 shallow water, strong light, high temperature, circulating water, a com- 

 paratively clean sea-floor, and a chemical composition of the water in- 

 suring a supply of calcium salts for the formation of the skeletons are 

 essential. 



