Clarksville weekly chronicle. (Clarksville, Tenn.) 1873-1890, 1879-07-26
The CabInets of .I.e g1s.iversity.
(CONTINUED.)

We should lose much, did W
fail to see the beautiful specimen
of Silicified Wood and of Wood
Opal showing perfectly the int
rior structure of the original vege
table mass, whose organic matte
has been interstitially, nolecule b,
molecule, replaced by the morgan
ic-interesting illustrations of th
process of DetrJactioa fern am
feature being retained, while tn
material has been changed.
a finely crystallizing mineral
| well represented in our collection
is Apatite, consisting essentially 0
Phosphate of Lime here are some
large green hexagonal prisms of it
lying snugly in a matrix of white
limestone, the contrast of colors be
ing very striking and effective. Il
is interesting to note that some min
eralogists consider it probable thai
this mineral has been derived in
many cases from animal fossils, as
bones contain very analogous in
gradients.
| The various forms of Silica, al
ready mentioned, consist of the BIZ
nary compound, known in Chem
istry as Silicon Di-oxide, { ST O2
but this substance does not always
exist in an isolated state; it is very
frequently found united with met
ais, and then forms an important
class of Salts which are denomina-
ted Silicates. 1t would, of course,
be improbable to give the catalogue
of this most numerous class of min
erals, the specimens of all of which
are to be seen on the shelves in the
University cabinet. Let few
names, such as may possess some
popular interest, suffice in this con-
nectiOn.
The Calcium Q4ime) group, whose
Carbonates, Sulphates, Fluorides
and Phosphates have been already
met with, has its representative,
too, among the SiIicates. Wallas-
tonite (named in honor of the dis
tinguished DR.. WalIaston, of Eng
land) often called Tabular Spar, is
Lime Silicate, of white color
rather pearIy luster and pleasing
aspect.
Under the head of Magnetism
Silicates, we find several very in
teresting minerals Tale, one of
the softest substances, of white or
green color, often occurring in foil
ated masses, and having a greasy
feeling when touched by the finger,
which latter is quite a characteristic
Of the magnesia compounds Stea-
tite or SOapstOne, we'll known in
powder as a material for polishing
and lubricating, as also for remOv-
ing grease spots. 1t may be saWn
into slabs for various purposes. Ser
pentine is a massive form, of the
same chemical constitution as the
foregoing minerals of a dark
green color, and takes a most beau
tiful polish. The celebrated Nerd
Antique marble consists Of granu-
lar limestone containing Serpentine
disseminated through its mass.
Meerschaum, so highly esteemed
nowadays for pipe bowls and cigar
holders, is, also, Hydrated Sill
cate of Magnesia, containing some
Iron and Alumina. Dana says of
variety from Anatolia "When
first dug up, it is soft, has a greasy
feel, and fathers like soap and on
this account it is used by the Tar
tars in washing their linen. 1t is
used for making the bowls of Turk
ish pipes, by process like that for
pottery ware. When imported in
to Germany, the bowls Of the pipes
are prepared by softening them first
in tallow, then in wax, and finally
polishing them" The name meer-
schaum signifies "sea-foam )" it is
so called because of its lightness
and its whitish color.
The class of Anhydrous Silicates
of Magnesia is very fully repre-
sented. The most important and
abundant genera of this class are
Pyroxene and Hornblende, each in
Guiding many varieties, among
which is found the mineral sub
stance called As5eSt0S, characterized
by its being in slender, faX-like
fibres, which Is sometimes woven
into cloth. 1t was used by the an
clients for the wicks of the lamps in
their temples. 1t is incombustible
and a poor conductor of heat. Its
Greek derivation indicates the first
property. All that would be nee
essary to cleanse garments made of
Asbestos, would be to throw them
into the fiames-p'gVfed 6y.fre.
We next come to the Alumina
group, which presents some strange
anomalies. For instance, here is a
rough-lOOking substance, approach
ing to a hexagonaI form of crystal
lization-so rude, that you would
not take the trouble to stoop to pick
il up-and By its side is richly
blue Sapphire, only inferior to the
diamond in value. These two very
dissimilar species are chemically
identical, both being pure oxide Of
Aluminium. The rough crystals
are called C0rundum, and when
triturated, afford the "emery pow
der" used by the ladies and Others,
for polishing purposes.
The Sapphire and lis unprepos-
sessing relative, Corundum, are
very hard, being excelled in this
regard by Diamond alone. The
typical color of Sapphire is blue
if. however, frequently assumes
other colors, as red (Oriental Ruby,
m