252 Mr Silliman on the 



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 to 8 per cent., that 

 it cannot be separated by any method resorted to, except by 

 frequent 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 ana- 

 lysis, by falling short of the amount required to complete the 

 100 parts, will invariably shew 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 below (particularly in 

 No. IV., but more or less in all), a large quantity of fatty (\) 

 matter separated, of a yellow colour and disagreeable pene- 

 trating 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 ethereal solution 

 yielded a yellow solid, resembling wax. It fuses below 

 200° F. A pungent irritating odour arose from the evapo- 

 ration of the ethereal 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 decom- 

 position 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 



