and Observations on the component Parts of Membrane. 361 



of coal afforded by these last, was more abundant than what 

 was obtained from those which were first mentioned. 



To these succeeded the experiments on the Millepores ; from 

 which it appeared, that 



Millepora ccerulea afforded loose detached portions of a gela- 

 tinous substance. 



Millepora alcicornis yielded the same, but in a more coherent 

 state. 



Millepora polymorpha remained unchanged in shape, and con- 

 sisted of a strong, white, opaque membrane, filled with a trans- 

 parent jelly. 



Lastly, Millepora cellulosa, Millepora fascialis, and Millepora 

 truncata, afforded membranaceous bodies, in a complete state of 

 organization ; and all these Millepores, when exposed to a low 

 red heat, yielded various quantities of coal, according to the 

 greater or less abundance of the gelatinous or membranaceous 

 substance. 



The universal and only hardening principle of these Madre- 

 pores and Millepores, was proved to be carbonate of lime, with 

 the single exception of Millepora polymorpha, which also appears 

 to be differently constructed from the other Millepora. With this 

 single exception, carbonate of lime seems to be the only harden- 

 ing substance in these bodies ; and, when every circumstance 

 is considered, an exact similarity is to be found between the 

 substance forming the various shells, and that which forms the 

 Madreporte and Milleporce ; and the nature of these bodies is 

 so completely the same, that the changes or gradations of the 

 one are to be found in the other. For the chemical characters 

 which distinguish the porcellaneous shells, are in a great mea- 

 sure approached by those of Madrepora virginea ; and those 



3 A 2 



