244 Foreign Notices in Mineralogy, 
by “ granular calcareous spar, blackish sphene, and an amor- 
phous mineral of a reddish colour resembling idocrase or 
garnet.”—It consists of 
a 
* Silic - 52.58, containing 26.45 of ogigen. 
i 44.45 S 12.49 
me, - . 
Magnesia, - oS |: eg 0.26 
Protoxide of Iron, 1.13 0.26 
_ Allumina a Trace 
Volatile matter 0.99 
99.83.” 
At a meeting of the Wernerian Society of Edinburgh, 
‘Mr. J. Deuchar read a paper containing: observations on 
the occasional appearance of water in the cavities of regular- 
ly shaped crystals, and on the porous nature of quartz, and 
other crystalline substances, as the probable cause of this 
circumstance. In this paper he supposes that natural and ar- 
tificial crystals have a similar origin, and that although the 
form: sess a peculiar compactness of cohesion, and tar- 
diness of solution, which do not belong to the latter, yet that 
the artificial ones, through length of time, would acquire a 
similar cohesion and insolubility. Mr. Deuchar holds, 
that the water of crystallization is in great excess, and that 
this excess under certain circumstances gradually decreases. 
He holds that the water escapes by capillary movement 
through the pores of the salt, till what he supposes to be the 
neutral state be acquired, when the salt becomes compact 
and insoluble. When any malformation of the nucleus pro- 
duces a cavity or partial vacuum in the interior of a crystal, 
then the capillary attraction may be exerted to that cavity a* 
well as to the surface; but that this is modified by various 
circumstances. By pouring hot water upon a crack in the 
mouth of a bottle, about three inches in length, it extended 
to five inches, but returned again when he stopped adding 
the hot water ; cracks in pieces of window glass were also 
extended by pressure, and contracted agam upon its remo- 
val; hence Mr. Deuchar concludes “that water may enter 
the void interstices of crystals, when aided by pressure, not 
nly from the porous nature of their particles, but also from 
their temporary$ display of rents during the application of ® 
high temperature.” _ 
b 
