. III. DIST. CHAR. Mode, 47 



the bones of various animals ; shells, corals,$c., and 

 the ligneous parts of plants and trees. 



The substances produced by the conversion of or- 

 ganic matter are chiefly three namely,, carbonate 

 of lime, charcoal or oxide of carbon, and bitumi- 

 nated substances. 



The first, carbonate of lime, or lime combined 

 with carbonic acid, is found in most conservata, in 

 which calcareous earth forms the basis or harden- 

 ing principle as in bones, shells, corals, &c. The 

 other principles, with which the calcareous earth 

 was united in the recent state, having disappeared, 

 and given place to the acid in question.f 



f The composition of recent bones has been already noticed ; 

 that of shells, corals, the coverings of echini, and other marine cal- 

 careous bodies, differs not only in the nature of the hardening prin- 

 ciple, (wliich in some is the same as in bone, phosphate of lime, in 

 others, carbonate of lime, and, in many, a mixture of both, vidt; 

 Hatchett. Phil. Trans. 1799. 1800.), but also in the state of the 

 connecting gfuten, as it presents itself in the form of a cartilaginous, 

 horny, or membranaceous matter, variously combined with the; 

 calcareous particles. It will be often doubtful, therefore, except 

 when the composition of the recent subject has been previously as- 

 certained, whether the calcareous earth, constituting a conserra- 

 tum of one of these bodies, exist in the same state as in the origi- 

 nal, or under a different modification ; and especially if-dcarlonaU, 

 whether the carbonic acid have or have not been derived from 

 the surrounding minerals. To those who may deem the subject 

 worthy of investigation* the following general statement, extracted 

 from Mr. Hatchett's observations on testaceous substances, 



