Evening star., 1896-02-29
THE ORIGIN OF PEARLS.
They Always Form Around a Foreign
Body-Cause of Iridescence.

They Always Form Around a Foreign
BOdy-Cause of Iridescence.
From the London Chronicle.
Prof Stewards lecture at the Royal In
stitution was about the shell-forming habits
of the lamellibranchs, or oyster family. The
shell-bearing mollusks he said, are oil en-
dowed by nature with the very valuable
capacity Of deposting beautiful films of
calcte or carbonate Of lime frcm the cells
Of their soft cuticle or outer skin. In this
way they build up their shells.
The detailed structure of the shell Is well
worth studying. The layers Of calcareous
matter nearest the cuticle are beautifully
smooth and polished, forming the. we'll
known mother-of-pearl. known to biologists
as nacre. The deposit takes the form of
exceedingly thin, semi-transparent films,
and 1t Is from this cause that the beautiful
tridescence of nacre arises. Brewster, many
years ago, thought he had proved conclu-
sively that this iridescence was due to ex-
tremely fine lines on the surface, because
a cast taken of the nacre in wax exhibited
the same irideScepce. Prof. Stewart men
toned hat he had repeated Brewster's ex-
pertinent, and found that the iridescence of
the wax as due to fine films of nacre adj
herring to 1t. 1t may now be taken for grant
ed that The nacre films produce what are
known as Interference" effects in dfffract-
ing light and give rainbow tints on the
same prin nciple as Newtons rings and soap
bubbles.
The usual source of pearls found within
the oyster appears to be the intrusion of
some small foreign body, which sets up an
irritation Of the cuticle. The only means
OF defense open to the mollusk is to deposit
a layer Of nacre round the irritating par
ticle, and thus cut it off from the soft,
tender skin. grain of sand, a small crus-
tacean. or diatom may slip in between
the lips. and, setting up irritation, provoke
the cuticle to deposit around it series of
fn
from time to time, like the skins Of an
onion, until ultimately the little nucleus is
completely encysted. and pearl is the re-
suit.
be seen in mother-of-pearl, for the oyster
applies tn. same remedy to all sorts Of for
eign bodies, of whatever character they
may be: Prof. Stewart Fad even seen little
nsh lmbedoed In the nacre. The Chinese,
with their ingenious habit Of turning nat
ural phenomena to account have taken ad-
vantage of this to artific;ally excite the
growth of pearls in oysters. favorite de-
wee IS TO l. sert IN H-shaped piece Of wire
into the mantle border, by means of which
ordinary pear-shaped pearls are produced.
But the pr ocess Is not cor fined to producing
ordinary pearls. Larger objects are insert
e cd and co2ted with nacre. especially metal
ngures OF Buddha. which yield much-priZed
copies in pearl Of that divinity, generally
used as charms kFt
"hen the Moose Sheds His Horns.
From the Minneapolis Journal
Very few people have ever seen a bull
moose shed his horns This Transformation
usually takes place between January l and
January 8. during which time the animal
Is very ugly. The bull moose in the Eller-
ton moose park II. Rcseau commenced
shedding his horns on the date mentioned,
and during the process performed some
queer antics. He would run and jump at
everything in his way, butt trees and
fences, and his mates were driven by the
pig fellow hither and thither. A kicking
Dronco was turned In the park, and for
few minutes the fight was terrific, the
nronco coming out winner with his heels.
FINALLY the moose backed away and made
e run for the horse. This was too much
1Sr the bronco, who fed for dear life. with
nneaa rne moose nse IN full pursuit The race was
the moose could be stopped and the horse
taken away from the enraged animal, which
was accomplished with no little trouble
and danger.