180 
I have given these examples to show some varieties de- 
pending on what is commonly called petrifaction, and also 
to show that the remains of organized substances have 
passed into the common soil from whence they in part 
originated, and are now become evident to us by the me- 
morials left as proofs of such existence. In Limestone 
many curious subjects are to be found ; but it is only in- 
tended here to give a general idea of them ; and after show- 
ing a few other sports of Nature in different substances, it 
is expected that the remainder will be pretty well understood 
in mineralogical hands. 
