712 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



the interior of which was filled with a transparent gelatinous substance. From 

 the solution I only obtained a large quantity of carbonate of lime. The next ex- 

 periment was made in a manner exactly similar to the former; but a piece of the 

 polished or uncoated red coral was now taken. The effects produced by the di- 

 luted acid were the same as before; but in the solution some loose portions of a 

 transparent yellow gelatinous substance were now only to be seen. The nitrated 

 solution was treated as in the former experiment, and afforded a considerable 

 quantity of carbonate of lime. As it was possible that the action of the nitric 

 acid, though much diluted, might be too powerful, I was induced to try the effects 

 of acetous acid, in which I immersed a piece of the red coral fn its natural state. 

 It was gradually dissolved, with a slow effervescence, and left an external tubulated 

 membrane, retaining the original form, and filled with a transparent gelatinous 

 substance, as in the first experiment. The solution, when filtrated, afforded car- 

 bonate of lime. 



A piece of the polished or uncoated red coral was treated with acetous acid, in a 

 similar manner. It was slowly dissolved, and left a transparent gelatinous substance 

 like that which has already been mentioned, excepting that it was not in detached 

 portions. This solution, like the former, only yielded carbonate of lime. It may 

 here be observed, that in each of the above related experiments, the red colour of 

 the coral was gradually destroyed, as the solution of the calcareous substance ad- 

 vanced, and could not afterwards by any means be restored; nor could any colour- 

 ing principle whatever be detected by the re-agents usually employed. 



A piece of red coral, in its natural or uncoated state, was exposed to a low red 

 heat, in a crucible, during about 10 minutes, at which time a faint smell of burnt 

 horn was to be perceived. When the coral was taken out of the crucible, it had 

 completely lost the red colour, and was become pale gray. It dissolved in dilute 

 nitric acid, with effervescence, and some animal coal was separated. To the filtra- 

 ted solution pure ammonia was added, and produced a very slight precipitate, which 

 was collected, and was afterwards dissolved in acetous acid. From this solution, 

 by the addition of acetite of lead, some phosphate of lead was obtained. The 

 carbonate of lime was afterwards precipitated in the usual manner. As the very 

 small portion of phosphate of lime discovered in the preceding experiment, and 

 which had escaped the action of the acids then employed, might be only contained 

 in the coating or epidermis, a piece of the polished or uncoated coral was treated 

 in a similar manner; but on examining the solution it afforded a small portion of 

 phosphate, with a large quantity of carbonate of lime; so that the result of this 

 experiment did not differ from that of the former. 



From the preceding experiments it appears, that the gorgonia nobilis or red coral, 

 consists of 2 parts; one of which is the stem, formed of a gelatinous substance, 

 hardened by carbonate of lime, and coloured by some unknown modification of 

 animal matter; the other is a membranaceous tube, which, like a cuticle or cortex, 

 coats the stem above-mentioned, and, when deprived of its hardening substance, 



