tm Shell and lione, 23 



The \'^rioiis folutions were filtrated, and were examined 

 by pure ammoniac and acetite of lead ; but I never obtained 

 any trace of phofphate of lime, nor of any other combinatioa 

 of phofphoric acid. 



The carbonate of lime was afterwards precipitated by car- 

 bonate of ammoniac; and from many experiments it ap- 

 peared, that porcellaneous fliells confill of carbonate of lime, 

 cemented by a very fmall portion of animal gluten. 



Previous to the experiments on lliells compofed of nacre, 

 or mother-of-pearl, I examined fome patellae from Madeira, 



When thefe were expofed to a red heat in a crucible, there 

 was a perceptible fmell, like that of horn, hair, or feathers. 



The proportion of carbonic matter depofited by the fubfe- 

 quent folution was more confiderable than that of the (hells 

 above mentioned, and the proportion of carbonate of lime 

 relative to their weight was lefs. 



When the recent (hells were immcrfeJ in very dilute nitric 

 acid, the epidermis was feparated, the whole of the carbo- 

 nate of lime was dilTolved, and a gtlalinous fubliance, nearly 

 litjuid, remained, but without retaining the figure of the 

 fhell, and without any fibrous appearance. 



Thefe (hells evidently, therefore, -contain a larger portion 

 of a more vilcid gelatinous fubftance than thofe before men- 

 tioned; but the folution feparated from the gelatinous fub- 

 liance afforded nothing but carbonate of lime. 



Experiments on Shells cbrnfofed nf Nacre, or Mother-of-P^arl. 



When the fliell of the common oyller was expofed to a 

 red heat, the effects \yere the lame as thofe obferved in the 

 patclke ; and the folution of the unburncd (hell was fimilar, 

 only the gelatinous part was of a greater confillency. 



A fpecies of the river mufclc was next fubje6ted to expe- 

 riment. This, when burned in a crucible, emitted much 

 fnioke, with a flrong fmell of burned cartilage, or horn ; the 

 fliell throughout became of a darkgrey, and exfoliated. By 

 Solution in the acids a large quantity of carbonic matter was 

 feparated ; and much lefs of carbonate of lime was obtained 

 from a given weight of the (hell than from thofe already 

 njcntioncd. 



Upon 



