14 
PROCEEDINGS OF THE PERTHSHIRE SOCIETY OF NATURAL SCIENCE. 
animal rose to the surface to catch the drops, which it 
turned into pearls.” In the Philosophical Transactions 
for 1674 there is an article, by a naturalist named 
Cristophorus Sardius, describing the pearls as the eggs of 
the mussel, which is a more plausible theory than the last, 
though I fear he would have to wait some time before such 
eggs came to maturity ! A more poetical idea was that 
the mussel took the dew-drops into its shell in the early 
morning, and by some magical process converted them 
into pearls. Thus Camden, an early naturalist, says :— 
“ They (i.e ., the mussels), by a kind of irregular motion, 
take in the dew and produce pearls.” The formation of 
pearls is now known to be purely accidental. When a 
particle of sand or any other foreign body gets under the 
mantle, the mussel, irritated by the friction produced, but 
unable to rid itself of the cause of annoyance, renders it as 
inoffensive as possible by covering it with a smooth coat¬ 
ing of mother-of-pearl, similar to that with which the 
shell is lined. That this is a reasonable explanation has 
frequently been proved by inserting a hard particle 
under the mantle, when, after a time, a pearl is generally 
formed. This circumstance has long been known to the 
Chinese, who introduce lead pellets and mother-of-pearl 
beads within the shells of mussels, and keep the latter 
alive in ponds until the pearls are formed. Linne tried 
a similar experiment by boring a small hole in the 
shell, and thus introducing particles of sand under the 
mantle, and it is said that it was chiefly owing to this 
supposed discovery of the method of procuring artifi¬ 
cial pearls that he was ennobled, although we now 
know that the discovery was originally made long 
before his time. Mr James G. Bertram, in a book 
entitled The Harvest of the Sea, says that pearl- 
fishers always select deformed or wrinkled shells 
as being more likely to contain pearls than those of 
a smooth surface. The explanation of this probably is, 
that the efforts made by the mussel to rid itself of its 
enemy prevent it from constructing its shell as regularly 
as it would have done had there been no cause of disturb¬ 
ance. 
Britain, and in particular Scotland, has long been 
noted for the production of fresh-water pearls. The 
earliest mention we have of them is in a passage of Pliny, 
in which he describes a breast-plate covered with British 
pearls, which was brought to Home by Julius Ctesar, and 
deposited by him in the Temple of Venus Genetrix. 
Some doubt exists as to whether these pearls were derived 
from Unio margaritiferus or from Mytilus edulis, the com¬ 
mon mussel of our sea-shores, but the balance of opinion 
appears to be in favour of the former. It has been 
affirmed that the fame of the British pearls was one of the 
causes of Caesar’s expedition to this country. The follow¬ 
ing interesting historical allusion to a pearl in the Crown 
of Scotland is taken from a book called Edinburgh, Old 
and New: —“ The great pearl in the apex of the Crown is 
alleged to be the same which in 1620 was found in the 
burn of Kellie, in Aberdeenshire, and was so large and 
beautiful that it was esteemed the best that had at any 
time been found in Scotland.” Sir Thomas Menzies, 
Provost of Aberdeen, obtaining this precious jewel, pre¬ 
sented it to James VI., who in requital “ gave him twelve 
or fourteen cauldron of victuals about Dunfermline, and 
the custom of certain merchant goods during his life.” 
This pearl had undoubtedly been obtained from Unio 
margaritferus. 
In recent times, the Tay, from Perth upwards, has 
been the principal seat of the pearl-fishery in Britain, 
but owing to the large number of mussels which have 
been destroyed by the fishers the number of pearls 
obtained has gradually diminished, so that the industry 
has now ceased to be one of any considerable importance. 
Still, you must all be familiar with the scene presented by 
the river during a drought in summer, when scores of 
children may be seen wading about in the shallow 
water searching for the coveted treasures. I have 
already mentioned that the mussels lie in the bed 
of the stream with the valves slightly apart. The 
fishers take advantage of this, when gathering the 
shells, to thrust a thin rod between the open valves, 
when the latter instantly close, and thus the mussel 
becomes the unconscious means of its own capture. Pearl¬ 
fishing cannot now be a very lucrative employment, as it 
is calculated that only about one in a hundred of the shells 
opened contain a pearl, while not more than one in a 
hundred of the pearls found is sufficiently perfect in form 
and pure in colour to be of use for ornamental purposes. 
The value of such pearls is from £1 to £2, though occa¬ 
sionally one is found which is worth as much as £10. The 
value of pearls sent from the Tay to London between the 
years 1761 and 1764 amounted to £10,000, which will serve 
to indicate how greatly the industry has fallen off in value 
since that time. I shall conclude by expressing the hope 
that it may be long indeed ere the ravages made upon the 
pearl mussel succeed in blotting out its name from our 
local fauna, and in rendering it only a thing of the past 
