each other* But it is certain home other, agent mult be concern,
ed in this operation, befides. mere attraaion, .otherwife all halts
would cryffalhze in the fame manner. Others have, therefore,
had recourfe to .feme kind .of polarity in the particles of each fait,
which determined them to arrange themfelves in fuch a certain
form; hut unlefs.we give a reafon for this polarity, we only exr
plain cryftallization by itfelf. One thing feen.s to have been,
overlooked by thofe who have endeavoured-to inveftigate this-
fubjeft, namely, that the faline particles do not only attraft one
another,, but they alfo attrafl fome part of. the water which
dillolves them.
Did they only attraft each other, tlie fait,' in fte a d o f cryftal,
ltzing would fall to the bottom as a powder ; whereas, a faline
cryftal. is compofed.of fait and water, as certainly as the body o f
an animal is eompofed of flelh and blood, or a vegetable of folid
matter and fap; if a faline cryftal is deprived o f its aqueous part,
, .a5 certam 7 its cryftalline form as i f it was deprived of
the faline part: It is, therefore, not improbable,- that cryftalliza.
tiomsafpec.es o f vegetation, and is accomplilhed. by the fame
ppwers to which the growth oS’ plants and animals are to be
alcnbed Some kinds of cryftallization refemble vegetation fo-
much, that we. can.fcarce. avoid attributing them to the fame-
caule....
.It has been imagined, that all the great operations in nature
may be reduced , to two principles, thofe o f cryftallization and
organization ; but thatoften they are fo concealed- as to be invifible.
-Encyclopaedia Britannica, p. 232.9.
vifible. Hence cryftallized fubftances have been often miftaken
for organized ones, and vice verfa. They differ, however, effen-
trially in their growth and origin. Organized beings fpring from
a germ, in which all the effential parts are concentrated, and
they grow b y intufception; whereas cryftallized fubftances in-
creafe by the fucceffive appofition o f certain molecules,. o f a determined
figure, which unite in one common mafs. Thus
cryftallized beings do not grow, properly fpeaking ; though their
fubftanee is augmented, they are not preformed, but formed
daily.
We have already fhewn, page 163, how to prepare the various
falts for microfcopical obfervations. The beautiful cryftalliza-
tions reprefented in PI. XXX. and.XXXI. were produced in the
manner there defcribed.
Figi-2,. Plate XXX. lhews- the microfcopical cryftals of nitre.
Thefe ftioot from the edges with very little heat, in flattilh figures,
of various lengths, and exceedingly tranfparent, the fides nearly
parallel, though rather jagged, and tapering to a point; after a.
number of thefe are formed, they often diflblve under, the eye,
and difappear entirely; but in a little time new {hoots will pulh
out, and the procefs go on afrefli. Beautiful ramifications are
formed round the edge, and many regular figures are to be ob-
ferved in different parts of the drop. Fig. 2 is the real fize of the
drop.
Fig. 3, Plate XXX. is a drop o f diftilled verdigreafe, as it appeared
when-viewed by the microfcope. There is a difference in
the-.'