708 PHILOSOPHICAL TRANSACTIONS. [ANNO 1800. 



figure of tlie madrepore. The clear solution being poured into another vessel 

 only afforded a large quantity of carbonate of lime. 



Madrepora fascicularis. — When this was put into very dilute nitric acid, a con- 

 siderable effervescence arose; and after some hours a tender membrane was left 

 which retained the original shape. Pure ammonia did not disturb the transparency 

 of this solution; but a copious precipitate of carbonate of lime was obtained, by 

 the addition of carbonate of ammonia. These experiments, on only a few of the 

 madrepores, sufficiently prove how similar they are, in composition, to shell; for 

 both consist of the same materials, subject to the like modifications. 



Millepora ccerulea. — This produced much effervescence, when immersed in very 

 dilute nitric acid. The blue colour disappeared, as the calcareous part was dis- 

 solved, and was not afterwards restored by ammonia. Some loose detached portions 

 of a gelatinous substance floated in the solution, which were separated by a filter. 

 The transparency of the solution was not disturbed by pure ammonia; but a copious 

 precipitate of carbonate of lime was produced by carbonate of pot-ash. 



Millepora alcicornis. — This millepore, when treated with very dilute nitric acid, 

 produced a great effervescence; and after a few hours a tender gelatinous substance 

 remained, which did not retain the figure of the millepore. Pure ammonia had 

 not any effect; but carbonate of ammonia precipitated a large quantity of car- 

 bonate of lime. 



Millepora polymorpha. — This produced an effervescence when put into dilute 

 nitric acid; and after some hours a substance remained, which completely retained 

 the original figure of the millepore. The substance which thus remained, was 

 composed of a strong white opaque membrane, which formed the external part; 

 the interior of this was filled with a transparent gelatinous substance. Ammonia 

 produced a very slight precipitate, which, being dissolved in acetous acid, was 

 proved to be phosphate of lime, by solution of acetite of lead. Carbonate of 

 soda afterwards precipitated a large quantity of carbonate of lime. 



Millepora cellulosa. — This millepore effervesced much with dilute nitric acid; 

 and when this had ceased, a finely perforated membrane remained, in structure and 

 appearance like the original substance. Ammonia did not produce any effect; but 

 a large quantity of carbonate of lime was obtained by carbonate of soda. 



Millepora fascia lis. — Th is resembled the former in every particular; and left a 

 membrane perfectly like the millepore. 



Millepora truncata. — When treated with dilute nitric acid, it effervesced much, 

 like the former; and after a few hours a semi-transparent membranaceous substance 

 remained, which exhibited completely the shape and structure of the original mille- 

 pore. Ammonia did not disturb the transparency of the solution ; but the whole 

 of the dissolved portion was precipitated, in the state of carbonate of lime, by 

 carbonate of ammonia. 



The remark lately made on the madrepores may here also be repeated, as the 

 composition of the millepores appears to be the same, with the single exception of 



