144 On Certain Cavities in Quartz, Se. 
careous spar for its disintegration by reducing it to quicklime, 
between which and water a. new chemical combination oceurs, 
which effects its final dissipation, and leaves the specimen as we 
find it, free from any traces of carbonate of lime, except the mere 
correspondence of the iden of the latter Sith the cavities of 
the former. 
The crystallized hexagonal ied of two of the specimens 
can be explained by either the agency of heat or water, as erys- 
tallization from solution can be artificially effected by evaporation, 
and afterwards can be again liquefied by heat, and re-crystallized 
by gradual cooling. — Yet the specimen rages leader 
would indicate an igneous origin. 
_ Whether the formation of these specimens can be attributed to 
cither of the above causes, or to both, or to neither of them, and 
at what particular geological period. they may have occurred my 
knowledge i is too limited positively to determine. Their conside- 
ration, too, may be more curious than useful, yet as they have not 
received any attention from the authors in my possession, I have 
taken it for granted that the specimens are rare, and that their 
history might be a slight contribution to science. "These motives 
have induced me to forward you an account of them, with my 
hasty views of their production, believing, too, that if they pos- 
real interest. my communication would not be pnwelcong 
and that if they do not, no harm could result. 
- P. 8. There is a communication on Spontaneous | ‘Combustion 
in Vol. xxxmrof your Journal, by Dr, James Mease,-and amang 
other instances is one taken from Hazard’s Register of Pennsyl- 
vania, of a piece of wood taking fire in the store of Mr. Adam 
Reigart of our city.. This statement differs from that made-to me 
by Mr. Reigart and his clerk, Mr. G: H. Whitaker, The wood 
was chestnut, quite solid, about eight inches long, and three or four 
wide, and cut smooth with a penknife. Two days before the 
burned wood was observed, they had washed the shelf and han- 
dled the wood with wet hands. When first noticed i¢was mot 
then on fire, but the most of it had been reduced to ashes. The : 
unconsumed portion was ragged and perforated,* and what is 
remarkable, not in the least charred, while the paint on the shelf | 
‘on which it lay was destroyed as by fire.. Mr. Whitaker still ba 
a portion of | of the wood and ashes, which he poninkeee a 
* __” Probably the combustion only took place at the points which had previously = 
been wet. 
* 
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