MYTILUS MUSCLE. 191 



This species now forming the genus Melagrina, 

 is much celebrated for producing pearls : though 

 so beautiful in appearance, they are thought to be 

 occasioned by a disease in the Mollusk, and 

 produced by a partial secretion of the substance 

 of which it forms the inner coating of its shell ; 

 this in the pearl is arranged in concentric layers. 

 Acids have the same effect upon pearls as upon 

 other carbonates of lime, and Cleopatra is said to 

 have dissolved in vinegar one of great value in 

 order to display her magnificence by this costly 

 draught. The pearl fishery is a very dangerous 

 employment ; it is principally carried on in the 

 Persian Gulf and in the neighbourhood of Ceylon ; 

 the season for the fishery lasts about a fortnight. 

 Numerous boats are dispatched to the station of 

 the pearl fishery, each containing twenty men, ten 

 of whom are employed in rowing and assisting 

 the divers. They descend alternately in parties 

 of five, and thus time is afforded for the men to 

 recover themselves after their violent exertion. 

 The diver has a rope attached under his arms, 

 the end of which is given to the men in the boat ; 

 round his neck is slung a net, distended at the 

 opening by a hoop : closing his nostrils, he com- 

 mits himself to the sea, with a perforated stone 

 of ten or twenty pounds weight affixed to his 

 foot, to accelerate his descent. He sinks gene- 

 rally a depth of twenty or thirty yards ; then 

 quickly proceeding to his work, he tears the 

 muscles from their bed, fills his net, makes a 



