(63) 
to which, to affix either appropriate names, or to 
describe, would be difficult. ‘ 
‘There are instances, where the internal part of an 
hexagonal prism is a triangular pyramid; and there 
are specimens, the faces of which are covered with 
crystals, which exhibit different stages of augmenta- 
tion, from the first projection of part of the hexa- 
gonal prism, near the base of a three-sided pyramid, 
until the pyramid is entirely envelopped, and becomes 
a perfect six-sided prism. Some are occasionally co- 
loured, and tinged with a coating of iron: some are 
opaque, and, at the same time, are covered with 
smaller crystals, that are transparent, and of another 
form. Why does this substance assume such a variety 
of forms? and, why, in the same place, will the 
crystals differ in their shape? These are questions 
of difficult. solution; and cannot, perhaps, like many 
other curious phcenomena, be fully explained, by 
any of the principles which have yet been offered 
to elucidate the abstruse science of crystalization. 
-In conclusion, it must not be omitted in this 
place, that the transparency of many of the ‘crystals 
o 
