150 
AMERICAN AGRICULTURIST 
[Apbox, 
Pearls— Wliat They Are and Slow 
Procured. 
The valuable jewels—we can hardly call them gems— 
known as pearls, are simply a rather common substance, 
pearl , in a peculiar form. Therefore, before we talk 
about pearls, it will be well to say something about pearl 
in general. The shells of various Mollusks, commonly 
called “ Shell-fish,” whether found in salt or in fresh wa¬ 
ter, show upon the inside what is known as a “ pearly 
lustre; ” the surface shows a great variety of colors as 
the position of the shell is changed, and we see, in very 
delicate tints, all the colors of the rainbow. Sometimes 
the shell of the common oyster is slightly pearly, but only 
indistinctly so, while the shells of the Unios and other 
Fig. 3.— FRESH-WATER MUSSEL — UniO. 
Mollusks, so common in fresh water streams and ponds, 
and commonly known as “ Fresh Water Clams,” or 
“ Mussels,” are often lined with the most beautiful pearl, 
and show brilliant colors. All shells are much alike— 
that is, they are limestone, and have much the same 
composition as common limestone and marble. The 
animal within the shell—the oyster, the snail, the fresh 
water clam, indeed all the Mollusks that have shells, 
ALL BUILD THEIR OWN SHELLS. 
Their shells are not something that comes to them 
from without, but they are built up by the animal itself 
from within. Many shells show by lines, on the outside, 
the rate of their yeurly growth. You will at once wonder 
if all shells are essentially the same, why all shells are 
not pearly. This cannot be well described without going 
into matters that would hardly interest yon, and I can 
only say in brief, that it is owing to the manner in which 
the material is put together. Rock candy, clear barley 
sugar, a lump of loaf-sugar, the grained appearance of 
peppermint drops, and the dead white of stick candy, 
are all very unlike in appear¬ 
ance, yet each is only pure 
sugar in a different form , in 
which the particles of sugar 
have a different effect upon 
light. Some of these Mollusks 
in forming their coverings, so 
deposit the carbonate of lime, 
to build up their shell, that this 
in those with the pearly lining 
DECOMPOSES OR BREAKS UT 
THE LIGHT, 
and shows the various colors of 
which white lieht is compos¬ 
ed. Yon know that a crack in 
a lump of ice will show all the 
colors of the rainbow, and that 
a soap-bubble, when blown thin, 
will show the most beautiful 
colors ; these common illustra¬ 
tions will allow you to under¬ 
stand how the minute particles 
of shell material, if put to¬ 
gether in a certain way, may 
have a similar effect upon light. 
The difference then, between 
pearl and common shell, is, 
that it is so put together that the pearl breaks up 
white or common light into colored light. The ani¬ 
mal in making its shell, whether pearly or not, takes 
great care that its interior, the case, or house in which 
its soft body is to live, shall be perfectly smooth and 
polished. We will suppose that by some accident, when 
the animal has its shell open and is taking in food, a 
grain of sand falls in, and gets between the soft body of 
the creature and its shell. The animal has no claws or 
other helps by which to get rid of this unwelcome guest 
to its house, and as it can not push it out, it covers over 
the grain of sand with its sbeii material, so that, its 
sharp corners being covered, it can get along with it as a 
round, smooth body, and as year after year it gives a new 
coat to the shell, it gives one to its troublesome visitor, 
and thus the grain of sand grows and becomes a pearl. 
ALL PEARLS ORIGINATE 
in this manner—an attempt of the Mollusk to cover up a 
grain of sand or other intruding substance that it cannot 
get rid of, and as it covers it with the same material us 
that ol which it builds its shell, it will be seen that only 
those Mollusks that have handsome pearly shells, will 
make handsome pearls. Pearls are very often found in 
the common oyster, but as the shell of that is nearly dead 
white, and very rarely pearly, so the pearls are dead white 
and of no beauty. It is in the Pearl-oyster, a large oyster¬ 
like Mollusk, the roundish shells of which are sometimes 
a foot across, that we find the most beautiful pearly lin¬ 
ing, and consequently the most beautiful pearls, when 
accident causes them to be formed. This Pearl-oyster, as 
it is called, is not very closely related to our edible oyster; 
naturalists call it Avicula margaritifera; it is found in 
the East Indian seas, and in the Pacific Ocean, opposite 
Mexico and Central America. The shells, known as 
“Mother of Pearl,” shown in fig. 1, are much used for 
making buttons and for a great variety of small ornamen¬ 
tal work. The Pearl-shells and Pearls are obtained by 
THE PEARL DIVERS. 
In the countries where they abound, there are regular 
pearl fisheries. The “oysters” are found at a depth of 
from 50 to 100 feet, and the boats go out with 10 divers 
and men to manage the boat and haul up the divers. Each 
diver has a rope, at lho end ol which is a stone weighing 
about 30 pounds, it has a loop for him to put his foot in, 
and also a sort of basket to hold his oysters. The en¬ 
graving, fig. 2, shows a pearl-fishing scene in the Persian 
Gulf. The men, when at the bottom, work as rapidly as 
possible in picking up the oysters, and placing them in 
the basket; the most experienced can stay below only 80 
seconds, and the majority are down but 60 seconds, be¬ 
fore they jerk the rope as a signal to be pulled up with 
their load. When the oysters are brought on shore, they 
are stacked up to die and decay, and as a consequence, 
a pearl-fishery is not a pleasant place. The best pearls 
are about the size of peas, but much larger ones are 
found. The largest pearl known, is two inches through. 
PEARLS IN FRESH WATER. 
As already stated, the shells of onr Unios or “Fresh 
Water Clams,” or “ Mussels,” as they are often called, 
have a beautifully pearly surface on the inside, and those 
sometimes produce pearls of great beauty. Fig. 3 shows 
the Unio in which pearls are most frequently found, of 
about half of the real size. Several years ago. the Unios 
in the New Jersey streams were remarkably productive 
of pearls, and there was a great excitement over them. 
Taking advantage of the fact that pearls are produced 
by gravel, or other matter within the shells of the 
Mollusk, various attempts have been made to produce 
pearls artificially. The Chinese are especially clever in 
MAKING PEARLS AT WILL. 
They keep the Unios, or fresh water clams, in tanks, 
where they can find them again, and dexterously slip in 
between the poorcreature and its shell, either some little 
bits of pearl-shell, or small leaden shot; they sometimes 
pul in tiny leaden images of Buddha, one of their many 
gods. These articles are in time covered with pearl, as 
shown in fig. 4, and the superstitious think it wonderful 
that the image of Buddha should appear upon the shell. 
Other attempts have been made to produce artificial pearls 
by boring through the shell and putting in sand, etc. 
Fig. 2 .— EAST INDIAN DIVERS GATHERING PEARLS. 
Fig. 4.— ARTIFICIAL PEARLS PRODUCED BY THE CHINESE. 
