286 
stance, and the filling up of the interstices with the lapidifying 
matter. 
But it still remained to determine if a correspondent organic matter 
existed in animal fossils. To ascertain this point, therefore, the various 
kinds of animal fossils noticed in this volume were subjected to a chemical 
examination, by which the most satisfactory proofs were obtained of the 
existence of this animal matter, and even of its retaining, in several 
instances, very much of its original form. 
This circumstance was beautifully illustrated by the examination of an 
entrochus of the lily encrinite, the particulars of which are mentioned 
page 166, and are illustrated by the engraving Plate XIII, Fig. 47. A 
similar examination of the fossil tubipore, Plate I. Fig. 1, was equally 
successful; the animal membrane belonging to the coral, from which 
the marble derived its origin, being rendered exceedingly evident. 
Indeed, in a subsequent examination of this marble, the success 
was far beyond expectation ; the animal membrane was displayed, 
retaining the general external form with the original colour of the 
coral. The experiment was performed with equal success with several 
other substances ; particularly with a piece of the Derbyshire entrochal 
marble, the animal membrane of which was rendered perfectly distinct. 
Other experiments have already convinced me that the presence of 
organic matter in animal fossils, of almost every kind, is sufficiently 
frequent to authorize, in the fullest manner, the opinion which I have 
already advanced, respecting the principles on which the process of 
petrifaction is accomplished. In the vegetable fossils, it is true, that 
the organic matter appears to have undergone a particular change, 
having been previously brought to the state of bitumen; and I have 
strong reasons, the result of actual observation, for believing that, 
in the animal fossils, a correspondent change has been previously in- 
duced, and that the animal matter has suffered a conversion into 
adipocire. 
