52 
EDIBLE BRITISH MOLLUSKS. 
1862, is an interesting account of an experiment 
made on oysters that had become so impregnated with 
copper as to be as green as verdigris. They were taken 
from Falmouth harbour. An attempt was made to 
extract the copper from them ; and, after putting a 
hundred or more into a large crucible, reducing them 
to ashes, and continuing to increase the heat until 
the copper was melted, the produce was a bright bead 
of pure copper, which, according to the description, 
would be about the size of a large piids head. Mr. 
Penwarne, who communicated this article to the ^ Field,^ 
adds, that the oysters may have lain on a lode, or the 
copper might have accumulated from the wash of the 
stamping-mills. This proves, without doubt, that 
shell-fish can be impregnated with copper, or other poi- 
sonous substances, which probably would affect those 
who ate them. Some persons consider that mussels are 
unwholesome if a small species of crab [Pinnotheres 
pisum or Pinnotheres veterum), which is sometimes 
found in their shells, is not carefully taken out ; others, 
that they are only fit for food in the winter months ; 
and by some on account of their feeding on the spawn 
of the star-fish, which is poisonous.* It is said that 
if a silver spoon is boiled with the mussels, and it turns 
black, it proves that they are poisonous, and not fit to 
be eaten. But, whatever may be the cause of the 
wholesale poisoning by these shell-fish, they have been 
the means of saving many poor from starvation in times 
of scarcity. Mr. Patterson, of Belfast, in his ^ Introduc- 
tion to Zoology,^ mentions having been informed by an 
old inhabitant of Holywood, near the above-mentioned 
town, that in 1792 or 1793 there was a great drought 
* Jeffreys, Brit. Concbology, vol. ii. p. 109. 
