36 Phosphate Rocks of South Carolina, 
Adamite epochs, and indirectly the geographical 
conditions under which they flourished and became 
extinct. 
‘“A distinction is sometimes made between /ossz/s 
and swb-fossils, as they are called. The latter are 
usually of more recent origin, and are only partially 
altered in texture; the former as a rule, date back to 
earlier epochs and the conversion into stone is com- 
plete. In the one case, the more volatile substances 
have been driven off from the plant, and the softer 
and more perishable tissues have disappeared from 
the animal, while mineral ingredients have been 
absorbed, to a greater or less extent in place of the 
organic matter lost. In the other case the vegetable, 
if not converted into coal, has been thoroughly 
changed by a slow process into stone, merely retain- 
ing its original organic form; and animal remains 
have undergone a similar metamorphosis, and are 
recognizable only through their forms and textures, 
which are unaltered. 
“What is the nature of this marvellous transforma- 
tion from the organic to the inorganic state? It is 
not the result of a combination, or chemical union of 
earthy matter with organic matter, but rather a grad- 
ual replacement of the latter by the former. Particle 
by particle the organic matter disappears, and parti- 
cle by particle the mineral matter takes its place ; 
and so delicately is the substitution effected that 
scarely a cell or a fibre is ever broken or displaced ! 
The nature of the petrifaction will depend, not so 
much upon the composition of the plant or animal, 
