APPENDIX. 



717 



afford sufficient precipitate for analysis. The carbonate of lime, by far the most abun- 

 dant constituent, was separately determined on one gramme, as sulphate of lime, and 

 from this the carbonate was calculated. The ratio of phosphates and fluorides of the 

 several bases to the entire mass, was also determined from a distinct portion of coral, two 

 grammes by weight; and from the data thus furnished, we have the means of safely 

 estimating the organic matter by the loss. 



" Organic Matter. This constituent of the corals deserves particular notice. Some 

 remarks have already been made on it, when speaking of the colouring matter of corals. 

 This organic matter is so intimately united, throughout the whole structure of the corals, 

 amounting to 4-8 per cent., that it cannot be separated by any method resorted to, ex- 

 cept by repeated deflagrations with the nitrate of ammonia. When reduced to the finest 

 impalpable powder, it may be digested in repeated doses of boiling water, until no trace of 

 organic matter is longer found in the water, and yet a careful analysis, by falling short 

 of the amount required to complete the 100 parts, will invariably show its presence. 

 The oxalate of lime obtained in their analysis, if ignited (as in the usual manner directed 

 for the estimation of lime), will always have a dark carbonaceous hue, derived from the 

 organic matter of the coral. 



" During the solution of considerable quantities of several corals, whose analyses are 

 given beyond (particularly in No. IV., but more or less in all), a large quantity of 

 fatty (?) matter separated, of a yellow colour and disagreeable penetrating odour, though 

 not fetid. It was easily seen floating on the surface of the solution, in transparent jelly-like 

 masses of a yellowish colour. It was insoluble in alcohol, but readily so in cold ether, 

 and the evaporation of its etherial solution yielded a yellow solid, resembling wax. It 

 fuses below 200 F. A pungent irritating odour arose from the evaporation of the etherial 

 solution near its close, which, acted powerfully on the eyes and nostrils. This volatile 

 principle may be analogous to that known, to proceed from the decomposition of fat 

 (acrolein ?). It deserves more attention than I have been able to give it, particularly as 

 it may perhaps be the source of the disagreeable odour of some limestones of coral 

 origin. 



" Analyses. The following tables exhibit a comprehensive view of the results of the 

 several analyses. The relative proportions of organic matter, carbonate of lime, and the 

 complex precipitate of phosphates and fluorides thrown down by lime-water, are first 

 given; and afterwards the definite composition of this precipitate in the nine species more 

 minutely investigated. 



Carbonate of lime, 

 Phosphates and fluorides, 

 Organic matter, 



Porites. Porites. Madrepora. 



No. 7. No. 8. No. 9 (II.) 



Carbonate of lime, 94-438 95-000 94-07 



Phosphates and fluorides, 2-100 1-650 0-745 



Organic matter, 3-462 3-350 4*448 



Madrepora. Madrepora. 



No. 10(111.) No. 11 (IV.) 



92-315 95-086 



0-600 0-300 



6-585 4-614 



