and Observations on Shell and Bone. 
33 3 
the age and habit of the animal which has produced them ; but 
I believe that I may, at least, venture to place some confidence 
in the foregoing experiments, as several others, made since the 
above was written, have tended to confirm them.* 
In the course of making the experiments which have been 
related, I examined the fossil bones of Gibraltar, as well as 
some glossopetrae or shark's teeth. The latter afforded phos- 
phate and carbonate of lime; but the carbonate of lime was 
visibly owing principally to the matter of the calcareous strata 
which had inclosed these teeth, and which had insinuated itself 
into the cavities left by the decomposition of the original carti- 
laginous substance. 
The bones of the Gibraltar rock also consist principally of 
phosphate of lime; and the cavities have been partly filled by the 
carbonate of lime which cements them together. 
Fossil bones resemble bones which, by combustion, have 
been deprived of their cartilaginous part ; for, they retain the 
figure of the original bone, without being bone in reality, as 
one of the most essential parts has been taken away. Now, _ 
such fossil or burned bones can no more be regarded as bone. 
* These experiments were repeated on bladder, which I chose in preference to any 
other membrane, as not being liable to ossification, and therefore likely to contain 
very little or no phosphate of lime. 
250 grains of dry hogs’ bladder, after incineration, left a residuum the weight of 
which did not exceed -ith of a grain. This was dissolved in diluted nitric acid ; and, 
upon adding pure ammoniac, some faint traces of phosphate of lime were observed. 
Now, as 250 grains of bladder did not afford more than ^th of a grain of residuum, 
of which only a part consisted of phosphate of lime, there is much reason to regard 
this experiment as an additional proof, that phosphate of lime is not an essential ingre- 
dient of membrane. 
MDCCXCIX. 
Xx 
