BIVALVE MOLLUSCANS. 261 



formed, and he has made it very probable that 

 this is often or generally the case, but still the 

 process just mentioned may take place when 

 accidental substances are introduced, and pro- 

 duce the warty excrescences, arid sometimes 

 loose misshapen pearls. 



The diving tackle consists of a large stone 

 suspended by a rope with a strong loop above 

 the stone to receive one foot of the diver, and 

 having also a slip-knot, and a basket formed of 

 a hoop and network which receives the other 

 foot. When he has fixed himself in this tackle 

 and is duly prepared, he holds his nostrils with 

 one hand, and pulling the running-knot with 

 the other, instantly descends when he reaches 

 the bottom he disengages his foot from the 

 stone, which is immediately drawn up to be 

 ready for the next diver. He at the bottom 

 throws himself on his face and collects every 

 thing he can lay hold of into the basket when 

 ready to ascend he jerks the rope and is speedily 

 hauled up, and working himself up the rope he 

 arrives at the surface sooner than the laden 

 basket. A minute and half or two minutes are 

 the utmost any diver remains under water. The 

 shark- charmers form a necessary part of the 

 company, by their incantations they are supposed 

 to possess the power of preventing these voracious 

 fishes from attacking the divers, and they will 

 not descend without their attendance ; where the 



