Rocks of the Florida Reefs. 65 



specimens which, when pulverized, will present homogeneous 

 powders of the same constitution. 



II. Source of Lime in the Growth of Corals. 



Marcet,* as early as 1823, observed carbonate of lime in 

 the sea-water near Portsmouth. Jackson t found it in two 

 specimens of sea water furnished by the United States Ex- 

 ploring Expedition ; one from 600 feet, and the other from 

 2700 feet below the surface. J. Davy J found the sea-water 

 of Carlisle Bay, Barbadoes, to contain about T o^o oth part of 

 carbonate of lime. There was found scarcely a trace near 

 the volcanic island of Fayal. White || is of the opinion that 

 it fails only near the surface ; but the elaborate analysis by 

 Bibra,§ of no less than ten specimens taken generally from 

 a depth of twelve feet, but in one instance from a depth of 

 four hundred and twenty feet, in various latitudes on both 

 sides of the equator, shews quite conclusively that it is not 

 a constant ingredient of sea-water. His analyses do not 

 mention a trace of carbonate of lime. The quantity found 

 by Davy is very nearly that which is soluble in water and is 

 obviously due to the calcareous marl which abounds near 

 the Barbadoes. 



The water from within the Keys was carefully analysed 

 in my laboratory ; it contained lime and sulphuric acid among 

 its ingredients, but not a trace of carbonic acid. 



The total want of carbonic acid in a water in which coral 

 life is so luxuriant, suggests naturally that the stone plant, 

 as well as the coral animal, possesses the power of abstract- 

 ing lime from the sulphate ; the change being due to double 

 decomposition with carbonate of ammonia excreted from the 

 plant and animal, yielding carbonate of lime, quite insoluble, 

 and sulphate of ammonia of the highest solubility. The 

 building up of the calcareous skeleton becomes, upon this 

 hypothesis, of exceeding simplicity. The surrounding ele- 



* Annals of Philosophy, April 1823, p. 261. 

 t Am. Jour. Science, [2] vol. v., p. 47. 



% Phil. Magazine, [3] xxxv., p. 232. [| lb., p. 308. 



§ Ann. de Chemie et de Pharmacie, lxxvii., 90. 

 VOL. LIV. NO. CVII. — JANUARY 1853. E 



