Shepherdstown register. [volume] (Shepherdstown, Va. [W. Va.]) 1849-1955, 1886-05-14
Chalk.

come? Most of us know that IL chalk Is
burnt the result is quicklime. Chalk
is, in fact, compound Of carbonic acid
gas and lime: so that, when chalk is
heated in kiln, the carbonic acid flies
away and lime is left. BY this method
we see the lime, but not the carbonic
acid. If some chalk be powdered and
dropped into strong vinegar, there is
great deal of bubbling and fixing going
on, and finally clear liquid, in which
no sign of chalk appears. Here We see
the carbonic acid in the bubbles; the
lime is dissolved in the vinegar, and so
vanishes from sight. There are many
ways of showing that chalk is composed
OF lime and carbonic acid, and chemists
sum up as result of experiments that
chalk is composed almost wholly of car
Donate Of lime. All sorts OF limestones
are compounds of carbonate of lime
more or less pure. TO the unJsSisted
eye chalk has the appearance of "a form
less, loose and open kind OF stone. But
suppose some be taken. rubbed 10 pow
der in water and after careful manipu-
lation n selection be made anG placed
under microscope, we find IL presents
totally different appearance. 1t is
composed of a number of minute graE-
ules, among which are innumerable
bodies, some smaller and some larger,
but on the average not more than the
l-l00 Of an inch in diameter, and having
well defined shape and structure.
These are shells of animals that lived
and died long ages ago, and have left
their shells as testimony that they
once existed. One of the commonest is
something like badly grown raspber-
ry. 1t is called globigerina, and some
specimens OF chalk consists of little else
than globigerin@ and granules. But 1t
might be asked, How is it known that
they once existed? 1t so happens that
chalky skeletons exactly similar to the
globigerina of the chalk-in fact, their
descendants-are being formed at the
present moment by minute creatures
which flourish in multitudes over a
large portion of the earth's crust covered
! by the ocean. The Atlantic ocean has
at different times and for different pur-
poses been sounded. In 1853, Lieu
tenant Brookes sounded between New
! foundland and the Azores, and brought
up some of the deep sea mud by the aid
of special sounding apparatus, and mi
croscOpists found this mud to be COM
posed almost entirely of globigerlne,
and very similar to those occurring in
the chalk. Again, when the enterprise
of laying a cable between Ireland and
! the United States was first undertaken,
! it became matter of immense import
ance to know not only the depth OF the
sea through the whole line along which
the cable was TO be laid, but the exact
nature of the bottom, to guard against
the chances of cutting and fraying the
strands of that costly rope. The ocean
for the whole length along which the
cable was to be laid was sounded, and
specimens brought up from the bottom
and examined. As result of these OPP
erations we know the contours and the
nature of the surface soil covered by the
North Atlantic for distance Of ! ZOO
miles from east to west, rs well as we
know any part of the dry land. 1t isg
prodigious plain, one Of the widest and
most even plains in the world-a very
fortunate thing for the cable. III the
sea were drained off wagon might be
driven all the way from Va!entia on the
west coast Of Ireland TO Trinity bay,
Newfoundland, and, except upon one
| sharp incline about two hundred miles
! from Valentia, It would not even be
necessary to put the skid on, so gentle
are the ascen.s and descents along that
long route. From Valentia the road
would run down the hill for 200 miles.
| Then would come the central plain 900
miles or so wide, the inequalities Of sur
! face of which would hardly be peTcept-
ible although the depth varies from
TO- 900 feet to $1,000 feeT, aud there are
places in which Mont Blanc might be
sunk without showing its peak above
water. Beyond this the ascent Oh the
American side commences, and gradu-
| ally rises TO the Newfoundland shore.
! Almost the whole of the bottom OF the
! central plain, which extends many hun
ireds Of miles north and south, is COW
cred by a fine mud, which, when brought
to the surface, dries In a grayish white
friable powder, very much like soft
grayish chalk, and examined chemically
is composed almost wholly Of carbonate
of lime. Examined under the micro
scope, we find it to consist IN great
measure Of globigeriDe shells. SO that
the deep sea mud Is substantially
"chalk." These globigerine have been
the shells Of very low organism. The
animal is in fact mere particle Of liy-
ing Jelly, without defined parts Of any
kind, without mouth. nerves, muscles
or distinct organs. Yet this formless
particle is capable Of feeding, growing
and multiplying, aud OF separating the
carbonate Of lime, which Is dissolved In
sea water. Therefore, globigeri nae are
exclusively marine animals, and there
is no doubt that the globigerine Of the
chalk lived under the same conditions
as they do now. Thus in all probability
chalk is the ancient mud Of deep sea.
| Here and there this hardened mud re-
veais the remains Of higher animals,
which have lived and died and have
left their hard parts In the mud. just as
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