52 EDIBLE BRITISH MOLLUSKS. 



15th, 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 pin's 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 w r ith 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 l 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. Conchology, vol. ii. p. 109. 



