318 Mr. Hatchett’s Experiments 
The proportion of carbonic matter deposited by the subse- 
quent solution, was more considerable than that of the shells 
abovementioned ; and the proportion of carbonate of lime, rela- 
tive to their weight, was less. 
When the recent shells were immersed in very dilute nitric 
acid, the epidermis was separated, the whole of the carbonate 
of lime was dissolved, and a gelatinous substance, nearly liquid, 
remained ; but without retaining the figure of the shell, and 
without any fibrous appearance. 
These shells evidently, therefore, contain a larger portion of 
a more viscid gelatinous substance than those before men- 
tioned; but the solution, separated from the gelatinous sub- 
stance, afforded nothing but carbonate of lime. 
Experiments on Shells composed of Nacre or Mother of Pearl. 
When the shell of the common oyster was exposed to a red 
heat, the effects were the same as those observed in the Patellae, 
and the solution of the unburned shell was similar, only the 
gelatinous part was rather of a greater consistency. 
A species of the river muscle was next subjected to ex- 
periment. This, when burned in a crucible, emitted much 
smoke, with a strong smell of burned cartilage or horn ; the 
shell throughout became of a dark gray, and exfoliated. By 
solution in the acids, a large quantity of carbonic matter was 
separated ; and much less of carbonate of lime was obtained, 
from a given weight of the shell, than from those already 
mentioned. 
Upon immersing an unburned shell in dilute nitric acid, a 
rapid solution and effervescence at first took place, but gradually 
