An Account of the Pearl Fifbery at Ceylon. 349 
mon. Between one and two hundred pearls have been found 
within-one oyfter. Such extravafations may be caufed by 
heterogeneous bodies, fuch as fand, coming in with the food, 
which the animal, to prevent difagreeable friction, covers 
with its glutinous matter, and which, as it is fucceffively 
fecreted, forms many regular Jamellz in the manner of the 
coats of an onion, or like different ftrata of bezoars, only 
much thinner; this is probable, for if we cut through the 
centre of a pearl, we often find a foreign particle, which. 
ought to be confidered as the nucleus, or primary caufe of 
its formation. The loofe pearls may originally have been 
produced within the body, and, on their increafe, may have 
feparated and fallen into the cavity of the fhell. Thofe- 
compact ones, fixed to the fhells, feem to be produced by 
- fimilar extravafation occafioned by the friction of fome 
roughnefs on the infide of the fhell. Thefe and the pearl- 
like nodes have a different afpect from the pearls, and are of 
a darker and bluer colour. In one of the former I found a 
pretty large, true, oval pearl, of a very clear water; while the 
node itfelf was of a dark blueith colour. The yellow or gold- 
coloured pearl, is the moft efteemed hy the natives; fome have 
a bright red Juftre; others are grey, or blackifh, without any 
fhining appearance, and of no value. Sometimes, when the 
grey lamella of a pearl is taken off, under it is found a beau- 
tiful genuine one; but it oftener happens that, after having 
feparated the firft coat, you find a worthlefs impure pearl. 
I tried feveral of them, taking one lamella off after another, 
and found clear and impure by turns; and in an impure 
pearl I met with one of a clear water, though in the centre 
of all I found a foreign particle. The largeft and moft per- 
feét pearl which I faw during my ftay at Condatchey was 
about the fize of a fmall piftol bullet, though I have been 
told fince my departure many others of the fame fize have 
been found. The {potted and irregular ones are fold cheap, 
and are chiefly ufed by the native phyficians as an ingredient 
in their medicines. 
We may judge with greater or leffer probability, by the 
appearance of the pearl fhell,* whether they contain pearls or 
hot, Thofe that have a thick ‘calcareous craft upon them, 
, to 
