PLATE 5. 
AN INCRUSTATION. CALCAREOUS EARTH. 
Organized bodies, incrusted with fossil matter, have been 
arranged with petrifactions by various authors, and in a 
part of this work, formerly given to the public, they were 
ranked as sueh. The system we have at present adopted 
will not allow of this. The annexed plate, however, 
exhibiting a very singular specimen of calcareous incrus-' 
tation, it has been thought expedient to retain, as an 
example of the mode nature at present pursues, in sur- 
rounding animal and vegetable substances with a mineral 
matrix — The first step towards petrifaction. 
Calcareous incrustations are frequent in Derbyshire ; they 
are found in all those streams and rivulets which run over 
limestone ; where they are daily formed by the deposition 
of calcareous earth on moss, bones*, &c. The scull, from 
which the present drawing was made, was found in a dif- 
ferent situation. — Some miners employed on a level, near 
Balceivdl, had followed, from the beginning of their work, 
the course of a small natural fissure in the roek, through 
which they were driving. After proceeding a few yards, 
they came to ix fault, or sudden division in the limestone, 
forming a kind of cave, several yards deep ; at the bottom 
* Most of the petrified bones of land animals described by authors, are 
merely incrustations. 
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