1888.] on Structure, Origin, and Distribution of Coral Beefs, dc. 255 



one-sixteenth of these organisms to die and fall to the bottom each 

 day, then they would take between 400 and 500 years to form a 

 deposit one inch in thickness. I give this calculation more to 

 indicate a method than to give even the roughest approximation to 

 a rate of accumulation of deposits. The experiments were too few 

 to warrant any definite deductions. 



The great oceanic currents moving westward at the rate of several 

 miles an hour, bear these shoals of pelagic organisms on to the face 

 of the reef, where millions of greedy mouths are ready and eager to 

 receive them. The corals and other organisms situated on the outer 

 and windward side of the reef receive the first and best supply ; 

 they are thus endowed with a greater amount of energy, and grow 

 faster and more luxuriantly there than on other portions of the reef; 

 the depth at which there is the most constant supply of this food is 

 several fathoms beneath the surface, and there too the corals are 

 found in most vigorous growth. It is only a relatively small quantity 

 of this pelagic food that enters the lagoon, the corals that there 

 struggle on in patches being largely supplied with the means of 

 existence from the larvae of reef-building animals. 



So many observations were made during the Challenger Expedi- 

 tion on the pelagic fauna inside and outside reefs that there is little, 

 if any, doubt in my mind that the food supply is a most important 

 factor in relation to the growth of corals in the different portions of 

 a reef. Actual observations were made 'on the feeding of corals at a 

 good many places, as well as numerous observations on the stomach 

 contents. These observations have been confirmed by Alexander 



It is not possible to state in what form the carbonate of lime that 

 is secreted in such enormous quantities by marine organisms exists 

 in oceanic waters. 



The following table shows the average composition of sea-water 

 salts, the acids and bases being combined in the way usually adopted 

 by chemists. 



Average Composition of Sea Salt. 



Chloride of sodium 77 ' 758 



Chloride of magnesium 10 • 878 



Sulphate of magnesium 4 • 737 



Sulphate of lime 3*600 



Sulphate of potash 2*465 



Bromide of magnesium • 217 



Carbonate of lime • 345 



100*000 



In the actual ocean water there are probably traces of every known 

 element, and it is impossible to say what is the precise amount of the 

 respective chlorides, sulphates, and carbonates'^present. Theoretically, 

 every base may be combined with every acid, and the whole solution 



