326 Cursory Remarks on 
this assumed contraction in the substance of 
Rotten-stone, it is evident, we may readily 
account for the greater proportion of alumine 
it exhibits, on comparing a given quantity of 
it, with an equal one of limestone.—But it 
will probably be advanced, that the hypothe- 
sis eventually supports more than we wish to 
prove; as, admitting the contraction of the 
matter forming Rotten-stone, any limestone 
holding a small quantity of alumine may be 
each other may easily be supposed, as a natural conse- 
quence of the removal of the calcareous matter ; but, that 
the structure of the original stone should remain, after this 
loss of matter, will not, perhaps, be as easily supposed or 
admitted.—However, as the ingredients of black lime- 
stones, &c. exist (it is probable) merely in the state of 
mixture, the extraction of any one of these constituent 
parts will certainly be less liable to destroy the general 
structure of the stone, than if the process had to act on 
principles chemically united. 
We have here considered the structure, or fracture of 
hard Rotten-stone to be immediately derived, generally 
speaking, from that of the original limestone ; but in some 
instances, particularly where the slaty structure is present, - 
it is rather, perhaps, the consequence of the contraction 
contended for, than the remains of any particular disposition 
of particles, which existed in the primary fossil.—We have, 
not unfrequently, observed the slaty structure in hard 
Rotten-stone, where no vestige of it appeared in the 
enclosed nuclei of limestone; though it must be observed, 
that these nuclei, in every other respect, were perfectly 
similar to those, in which such structure was very evident. 
