VOL. XC.] PHILOSOPHICAL TBANSACTIONS. JOQ 



millepora polymorpha, which afforded some slight traces of phosphate of lime. 

 But time and future experiments will show whether this was an accidental circum- 

 stance, or whether the millepore polymorpha is thus distinctly characterised. It is 

 likewise necessary to add, that when these various madrepores and millepores were 

 exposed to red heat, in a crucible, they emitted smoke, with the smell of burnt 

 horn or feathers, became tinged with a paler or deeper gray colour, and when dis- 

 solved in acids deposited more or less animal coal, in proportion to the quantity of 

 the gelatinous or membranaceous substance detected by the experiments lately 

 described*. 



Tubipora musica. — Of the tubiporae, I had only an opportunity to examine this 

 species. Like the former substances, it was immersed in an acid, and on this oc- 

 casion I employed the acetous acid. A great effervescence was produced, and the 

 red colour was destroyed, in proportion as the calcareous part was dissolved. When 

 the solution was completely effected, some loose particles of a tender membrane 

 floated in the liquor, and were separated by a filter. Pure ammonia added to the 

 solution, produced a precipitate; which proved to be argill, accidentally lodged in 

 the interstices of the tubipore. To the filtrated liquor, carbonate of potash was 

 added, and precipitated a large quantity of carbonate of lime. 



Flustra foliacea. — When this was immersed in very dilute nitric acid, an effer- 

 vescence of short duration took place; and, when this had ceased, the flustra ap- 

 peared like a finely reticulated membrane, which retained the original shape. Pure 

 ammonia being added to the filtrated solution, produced a slight precipitate; which, 

 being dissolved in acetous acid, was proved, by acetite of lead, to be phosphate of 

 lime. Solution of carbonate of ammonia was then added to the liquor from which 

 the phosphate of lime had been separated, and produced a copious precipitate of 

 carbonate of lime. When the flustra foliacea was exposed to a low red heat, in a 

 crucible, it emitted a smell like burnt horn, but retained its shape, by reason of 

 the carbonate of lime with which it was coated. The flustra thus burnt, when 

 dissolved in dilute nitric acid, deposited some animal coal ; but in other respects 

 the present solution resembled the former nitric solution of this substance when in 

 a recent state. The flustra foliacea, when long digested with boiling distilled 

 water, communicated to it a pale brownish tinge. Infusion of oak bark being 

 then poured into the liquor, did not produce any visible effect, even after 24 

 hours had elapsed; but nitro-muriate of tin formed a white cloud, in the space of 

 a few minutes. 



Corallina Opuntia. — This being put into very dilute nitric acid, produced, like 

 the flustra foliacea, an effervescence of short duration. The coralline then re- 

 mained in a membranaceous state, and retained the original figure. To the filtra- 

 ted solution some pure ammonia was added, but it scarcely produced any visible 



* The order in which these experiments are placed, is not that according to which they were made; 

 but it has been adopted, because it shows more evidently the gradations of the membranaceous sub- 

 stances. — Orig. 



