MOLLUSCA. 189 



which were abundant in produce the previous 

 season. 



In Europe the white pearls are most valued, 

 whilst the inhabitants of Ceylon prefer those of a 

 rose colour, and the Indians and other Asiatic 

 people those which are yellow. Pearls, indeed, 

 vary much in colour and appearance; some are 

 quite black, others dark blue or purple, with a 

 silvery or golden lustre. 



During the process of fishing, few places are 

 more lively than the western point of Ceylon. The 

 shells and cleansed pearls are bought and sold on 

 the spot, in small bamboo huts erected for the pur- 

 pose ; and, besides this trade, the confluence of 

 crowds of strangers from different countries attracts 

 dealers in all sorts of merchandize. The long line 

 of huts is a continuously animated bazaar ; all is life 

 and activity. But as soon as the fishery closes, 

 scarcely a human being, or even a habitation, can 

 be seen for miles, and the most dreary solitude pre- 

 vails until the ensuing year. 



According to Woodward, the largest pearl known 

 is said to belong to a Mr. Hunt. It measures two 

 inches in length and four inches in circumference, 

 weighing 1800 grains. 



The nacreous lustre of the pearl-shell is an 

 optical phenomenon, termed interference ; it occurs 

 on glass which has lain in the earth for a length of 



