268 PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



3.2 to 3.0 parts per 10,000, or an increase of temperature 2° C. would result ulti- 

 mately in the precipitation of about 2 grams CaCOa from every cubic meter of a 

 solution saturated with it. Consequently, since there is reason to believe that the 

 surface layers of the sea (except in the Polar regions and within cold currents) are 

 substantially saturated with calcite, precipitation is to be expected wherever the 

 water is being warmed, or is losing CO2, or both, and this independently of any 

 other agencies. Indeed, these inorganic factors may not safely be left out of 

 account, no matter what be the agency inducing the precipitation; for there appears 

 to be a correlation in that calcareous organisms are more abundant the more nearly 

 satuated with CaCOs the water is. The view, here emphasized, of the importance 

 of the inorganic factors, does not exclude the other views which have been proposed 

 to account for the deposition of limestones, and is not in conflict with any facts 

 which have been definitely ascertained. Its precise importance could be established 

 only by accurate determination of temperature, salinity and, particularly, of con- 

 centration of CO2 — free and total — of the water, carried out systematically over 

 the ocean; such an investigation would have an important bearing on many biologi- 

 cal as well as geological questions, and would enable us ultimately to correlate the 

 position and rate of growth of some limestone deposits with cosmogonic factors 

 in a much more satisfactory way than has yet been done." 



A very important contribution to the study of the solubility of calcite 

 in sea-water, by Dr. R. C. Wells, appears on pages 316-318 of this volume. 



It seems to me that all lines of evidence converge and give the same 

 result, which is that in the shoal waters of the tropics ocean water does not 

 dissolve calcium carbonate, but that the contrary process — precipitation by 

 both inorganic and organic (bacterial) agencies — -is taking place. Conditions 

 in the deep sea, and perhaps in the cold waters of high latitudes, are different. 

 For the reasons stated, it is my conclusion that the disappearance of fine 

 material from behind the reefs at Murray Island, Australia, and Cocoanut 

 Point, Andros Island, Bahamas, is due to washing away of the fine material by 

 currents, which are probably caused, in large part at least, by winds and tides. 



Such phenomena as those exhibited at Murray Island and at Cocoanut 

 Point are localized. Coral reefs and their associated phenomena do not occur 

 everywhere, but under certain definite ecologic conditions. Bottom deposits 

 formed under other conditions will now be discussed. 



FINELY DIVIDED MUD FROM STAGNANT AREAS IN SOUTH BIGHT. 



(Sample No. 79, see plate 95.) 



The results of a mechanical analysis of a specimen, No. 79, are given in the 

 first table on page 269; the percentage of MgCOs (hypothetical combination) 

 is stated in the table on page 270. For position of stations indicated by the 

 field numbers see plate 95. 



Comparison of the mechanical analysis of sample 79 with the Murray 

 Island and Cocoanut Point samples shows that in the former the percentage of 

 particles of silt and clay size is 57.6, and only from 1.725 to 1.75 (averages) in 

 the latter; while the chemical analyses indicate 2.56 per cent MgCOa for the 

 former, and from 5. 24 to 5. 745 (averages) for the latter. Thedepositsobviously 

 belong to different classes. At station 79, besides the accumulation of fine 



