Experiments and Obftrvations on Shell and Bone, '501 



The dlflolved portion was examined by the above-mentioned precipltants 5 and in -ex- 

 periments where the quantity of the fubftancc would permit, the phofphoric acid was alfo 

 feparated by nitric or fulphuric acid. The phofphoric acid thus obtained, was proved after 

 concentration by experiments, which being ufually employed for fuch purpofes, are too 

 well known to require defcription. 



It is neceflary moreover to obferve, that as the fubfianees examined were very numerous, 

 and my principal objedl was to difcover the mod prominent chara£lers In them, I did not 

 for the prefent attempt In general, to afcertain minutely the proportions, fo much as the 

 number and quality of their refpeftlve ingredients. 



The greater part, If not all, of marine fhells, appear to be of two defcriptlons In refpe£t 

 to tht fubftance of which they are compofed. Thofe which will be firft noticed have a 

 porcellaneous afpedt, with an enamelled furface, and when broken, are often in a flight 

 degree, of a fibrous texture. 



■ The fliells of the other divlfion have generally, if not always, a ftrong epidermis, under 

 which is the fliell, principally or intirely compofed of the fubftance called nacre, or 

 mother of pearl. 



Of the porcellaneous fhells, various fpecies of voluta, cyprsea, and others of a fimllar 

 nature were examined. 



Of the fliells compofed of nacre, or mother of pearl, I fele£led the oyfler, the river 

 mufcle, the haliotls iris, and the turbo olearius. 



Experiments on -Porcellaneous Shells, 



Shells of this defcription, when expofed to a red heat in a crucible during about a quarter 

 of an hour, crackled and loft the colours of their>namelled furface ; they did not emit any 

 apparent fmoke, nor any fmell like that of burnt horn, or cartilage. Their figure re- 

 mained unchanged, excepting a few flaws; and they became of an opaque -white,- tinged 

 partially with pale gr^y, but retained part of their original glofs. 



The fliells which had not been expofed to fire, (whetlier intlrc or in powder) dlflolved 

 with great efFervefcence in the various acids ; and the folutlon afterwards remained colour- 

 lefs and tranfparent. 



But the fhells which had been burned, upon being dlflolved, depoCted a very fmall quan - 

 tity of animal coal ; and thereby the prefence of fome gluten was denoted, although the 

 .proportion was too fmall to be difcovered in the folutlon of the fhells which had not been 

 burned. 



The various folutions were filtrated, and were examined by pure ammoniac and acetitc 

 of lead -, but I never obtained any trace of phofphate of lime, nor of any other combina- 

 tion of phofphoric acid. 



The carbonate of lime was afterwards precipitated by carbonate of ammoniac ; and from 

 Vol. Ill — ^February 1800. 3T many 



