288 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



(5) Other classes of deposits will be recognized, but at present it appears 

 advisable to concentrate attention on the five or six mentioned in the fore- 

 going paragraphs. 



(6) No appreciable terrigenous material (Si0 2 and A1 2 3 ) reaches the 

 Bahamas. The percentage of Fe 2 3 , although only about 0.1 per cent, is 

 sufficient to produce iron stains and red earth when secondarily concentrated. 

 Some terrigenous material, mostly quartz sand, is washed into Biscayne Bay, 

 Florida, and into the sounds south of it, but otherwise practically none 

 reaches the key and reef region. The Florida area is therefore a perfect 

 example of limestones forming in shoal water near a land area which is not 

 crossed by large streams. The Fe 2 3 content of the Florida samples seems 

 somewhat higher, up to about 0.37 per cent, than that of the Bahama sam- 

 ples. A small amount of CaS0 4 seems persistently present; this fact is to be 

 correlated with the formation of aragonite, which is so abundant in the chem- 

 ically precipitated muds and in the Pleistocene oolites; Ca 3 P 2 8 is present 

 only as traces. 



(7) Shore material, subjected to wetting and drying by the rise and fall 

 of the tides, shows a higher magnesia content than material otherwise similar 

 but not subject to such influences. There has apparently been a secondary 

 concentration of magnesia. 



(8) Reconsideration of the evidence bearing upon the precipitation of 

 CaC0 3 in tropical and subtropical waters and the possibility of its re-solution 

 by ocean-water leads to the conclusion that precipitation is resulting from 

 both organic and inorganic agencies, and that no appreciable re-solution is 

 taking place in such waters; but there is solution in the depths of the ocean 

 where the temperature is low, and perhaps in the surface waters of high 



latitudes. 



(9) Although much progress has been made toward understanding the 

 formation of oolite grains, the oolitic muds, should they be indurated, would 

 not be precisely the same as the oolitic rocks now elevated above sea-level. 

 The former contain a larger percentage of MgC0 3 than the latter, and the 

 zonal structure is not so highly developed. The agencies involved in the 

 formation of the concentric shells of the grains need further study. 



(10) Requisites for adequately understanding the C0 2 and CaC0 3 rela- 

 tions in sea-water are (a) more accurate records of temperature and salinity 

 in the ocean; (b) accurate determinations of the C0 2 content of the air above 

 the water; and (c) further study of the C0 2 content (free and total) of the 

 water. 1 



■It is my desire to give such support as I can command to the suggestions made by Messrs. Johnston, Merwin, 

 and Williamson. The article by Messrs. Dole and Chambers (pp. 299-3 15) is a valuable contribution to the salinity 

 of the ocean-water at Fowey Rocks, Florida, and in it may be found references to variations in salinity in the 

 Floridian and Bahaman regions. Dr. Wells's study of the solubility of calcite in sea-water in contact with the 

 atmosphere, and its variation with temperature, is based on the same water on which Messrs. Dole and Chambers 

 report, and his results follow theirs, pages 316-318. The large amount of information on the temperature of 

 Florida waters is presented immediately after the paper by Dr. Wells. 



