264 SUMMIT OF PARNASSUS. 
CHAP, to a considerable depth. Among these, we 
. found a specimen of homogeneous limestone^ 
which had separated from its parent mass by 
spontaneous decomposition; and thus, being 
exposed to accidental fracture, exhibited the 
primary form of a regularly crystallized car- 
bonate ; being a rhomboid, whose obtuse angle 
precisely equals that of Iceland spar. An inci- 
pient transition may also be noticed, in the 
same specimen, towards a secondary form, in 
the neat truncation of one of the solid angles of 
the rhomb'. This first suggested to the author 
a fact since confirmed by subsequent obser- 
vations, that, in all homogeneous minerals, such 
is the tendency towards crystallization, that 
the inclination of surfaces disclosed by fracture 
will frequently point out the degree of inclina- 
tion of the lateral planes belonging to the 
primary crystal; and thereby determine the 
nature of the stone, and of its chemical con- 
stituents. Mineralogists, greatly his superiors 
in the science, had before proved that this is 
true with regard to the fragments of substances 
that have resulted from a regular process of 
(1) Seethe F/jgne^e to this Chapter. 
