MISCELLANEA^ 129 



secrete a verj^ important proportion of silica, and that of the salts, 

 the fluates" (should resid Jluorides) "greatly exceed in amount the 

 carbonates." 



The reader is left to understand, that the analyses quoted are in- 

 tended to represent the entire chemical constitution of the four 

 species of corals named, and if so, to infer that carbonate of lime is 

 not recognized by the analyst as an ingredient of corals, and that 

 lime is present only as a minor constituent. The absurdity of such 

 an inference is so plain, that no danger perhaps exists of its being 

 made ; and as the name of no analyst is given, on whose authority 

 so singular a statement is based, there is no probability of its being 

 an injury to the chemical reputation of the writer. It is however 

 for this reason none the less proper that so important an error should 

 be corrected. 



The original memoir on the composition of calcareous corals was 

 published in the ' Report on Zoophytes ' by J. D. Dana*, and has 

 since been re-published in several scientific journals f. Thirty-five 

 species of corals were examined in these researches, and the general 

 result was that they were composed as follows : — 



' ' '^erage Constitution of Thirty-Jive species of Corals. 



Carbonate of lime 91-00 to 96*00 



Phosphates and fluorides of lime and mag-~1 



nesia, with silica, lime, alumina and > 0*50 to 2*50 



oxide of iron J 



Organic matter iw. 1 . . Jtji?-»-(. 2*70 to 8*30 



Two sets of analyses were made; bile to determine the general 

 constitution as above, another to determine, by an entirely indepen- 

 dent examination, the composition of that complex portion deno- 

 minated in the memoir as phosphates and fluorides. It is here that 

 the error in question arises. You have cited four of these ultimate 

 analyses of about 1 per centum of the entire mass of the coral zoo- 

 phyte, in such a manner as to leave it to be understood that they 

 represented the constitution of the entire mass. 



You justly remark that these analyses suggest some interesting 

 investigations on the probable origin of certain minerals from the 

 coral secretions. Allow me to call your attention to a short paper 

 by Mr. Dana in the July number of the ' American Journal,' p. 88 

 (also in the London, Ed. and D. Phil. Mag. for Sept. 1846, p. 245), 

 " On the Occurrence of Fluor Spar, Apatite and Chondrodite in 

 Limestone." This paper contains some of the deductions which 

 naturally proceed from the coral analyses in question. 



Your obedient servant, 



B. SiLLIMAN, JUN. 



* United States' Exploring Expedition in the years 1838 — 1842. Report on 

 Zoophytes, by J. I). Dana. 4to, pp. 740: — p. 712. 



t American Journal of Science, March 1846, p. 189; Jameson's Edinburgh 

 Journal, April 1846, p. 243 ; Archives des Sciences Physiques etNaturelles, Supp. 

 H la Bibliothcque Univcrsclle, April 1846, p. 319. 



VOL. II. — PAKT ir. M 



