60 THE BERMUDA ISLANDS. 



tion of lime is concerned, there is either existing stability in 

 the sea, or that the different shell-bearing animals remove less 

 of the formative material for their own purposes than the sea 

 receives from continental erosion. In the calculation before 

 made we have used as a basis merely the quantity of lime-car- 

 bonate carried out in solution by rivers; to this must neces- 

 sarily be added that which is derived directly by the sea 

 through its own breakages the wear of the coast-line and 

 the other salts of lime of which no account has been taken. If 

 we double the quantity that has been assumed we will proba- 

 bly more than cover the available supply ; a rate of accumula- 

 tion, therefore, of one foot in 50,000 years would be the result. 

 It is needless to say that such a slow accumulation is hardly 

 compatible with any notion of growth from great depths, and 

 that it is entirely opposed to the view which holds to the 

 formation of giant banks leading up to the zone of coral life.* 

 But in what, it might be asked, lies the direct evidence that 

 giant banks are being built up through organic accumulations? 

 Is it merely the finding of foraminiferal and pteropod ooze on 

 projecting knobs of the ocean bottom ? This is not a new con- 

 dition, and it is practically repeated in the Globigerina ooze 

 which covers much of the oceanic floor. It would, indeed, be 

 remarkable if such deposits did not exist, but their presence 

 gives no answer to the possibility of building up giant banks 

 under the conditions which would be considered necessary for 

 the making of coral islands. No one has more carefully studied, 

 or is better acquainted with, the Florida reefs than Alexander 

 Agassiz, and perhaps no class of reefs has been more frequently 

 appealed to in the recent discussion of coral structures than 

 those examined by this authority. We are informed by Mr. 

 Agassiz that these reefs are merely organic growths and ac- 



*In evidence of the possible rapid accumulation of a foraminiferal and 

 pteropod deposit, and the building up of submarine banks, Prof. Hickson (Address be- 

 fore British Assoc., Bath, 1888) instances the case of the basal limestone of the 

 elevated reefs of the Solomon Islands, to which attention has been called by Guppy. 

 But manifestly this limestone was formed in shallow water, where the conditions for 

 rapid organic accumulation are almost infinitely more favorable than they are in deep 

 water. 



