372 
THE OCEAN WORLD. 
from various molluscs. He suggested bringing together a number ol 
mussels, piercing holes in their shells with an auger in order to pr°' 
duce a wound, and afterwards pack them for five or six years to 
give the pearl time to form. The Swedish Government consented to 
try the experiment, and long did so in secret ; pearls were produced, 
but they were of no value, and the enterprise was abandoned as un- 
successful. 
Scottish pearls were much celebrated in the middle ages, and 
between the years 1761 and 1784 pearls to the value of £10,000 
were sent to London from the rivers Tay and Isla ; “ and the trade 
carried on in the corresponding years in the present century,” say 3 
Mr. Bertram, “ is far more than double that amount.” The pearl, 
according to Mr. Bertram, is found in a variety of the mussel, which 13 
characterised by the valves being united by a broad hinge, and having 
a strong fibrous byssus, with which it attaches itself to other shells, fo 
rocks, and other solid substances. “ The pearl fisheries of Scotland, 
he adds, “ may become a source of wealth to the people living on the 
large rivers, if prudently conducted.” Mr. Unger, a dealer in ger° 9 
in Edinburgh, having discerned the capabilities of the Scotch pe*^ 
as a gem of value, has established a scale of prices which he gives fo 1 
them, according to their size and quality ; and it is now' a fact tha* 
the beautiful pink-hued pearls of our Scottish streams are admir eC * 
beyond the orient pearl. Empresses and queens, and royal and nobk 
ladies, have made large purchases of those gems; and Mr. Ung eI 
estimates the sum paid to pearl-finders in the summer of 1864 ^ 
£10,0u0. The localities successfully fished have been the classi c 
Boon, the Forth, the Tay, the Don, the Spey, the Isla, and most of 
the Highland rivers of noto. 
Among molluscs, the genus Tridacnm furnish the largest shell 3 
known among Acephalous Molluscs. The historian of the wars 
Alexander the Great speaks of oysters inhabiting the Indian O ceaU 
which were more than a foot long ; these were probably Trida B,uh ’ 
the shells of which were most likely to be seen by the Macedonia 11 
conquerors. The valves of Tridacna gigas are sometimes found a 
yard and a half in length, and weighing five hundred pounds. 
nificent examples may be seen in the church of Saint Sulpice, 
where they hold the holy water. These beautiful shells were the g J 
of the Venetian Republic to Francis I. Under Louis XIV-, ^ 
