Bocks of the Florida Reefs. 67 



mass of Meandrina, a foot in diameter, were reduced to pow- 

 der, washed with hot water until the chloride of sodium was 

 all removed, and their specific gravity ascertained by Storer. 

 The average of three specimens from the centre, three from 

 the middle, and two from the periphery, gave the following 

 specific gravities : — 



Centre. Middle. Periphery. 



2,695 2,749 2,785 



These results so far support the affirmative of the sugges- 

 tion above, as to make a repetition of the determinations 

 desirable. 



The chief conclusions to which the above research has 

 conducted are : — 



I. That the submerged or oolitic rock has been solidified 

 by the infiltration of finely powdered (not dissolved) carbonate 

 of lime, increasing the points of contact ; and the introduc- 

 tion of a small quantity of animal mucilaginous matter, 

 serving the same purpose as the carbonate of lime, that of 

 increasing the cohesive attraction. 



II. That the surface rock has been solidified by having, in 

 addition to the above agencies, the aid of a series of chemi- 

 cal decompositions and recompositions resulting in the for- 

 mation of a cement. 



And I may add that it lends support to the suggestion, 



III. That the carbonate of lime of corals is derived from 

 the sulphate in sea-water, by double decomposition with the 

 carbonate of ammonia exhaled from the living animal. — (Sil- 

 liman's American Journal, vol. xiv. 2d Series, No. 41, 

 p. 224.) 



E 2 



