Mother -of -Pear I and its Uses. 395 



them time to grow to maturity, as to be now of little value. 

 This is a mistake in both instances ; the best of the shell 

 lies still in deep water, and in the great coral caverns 

 underneath the exhausted shelves, from whence the savages, 

 by judicious persuasion, can be easily induced to bring 

 them to the surface. There are some lagoons in which 

 any great quantity, and in some cases no shell whatever, 

 is now supposed to exist ; yet there are at those places very 

 considerable deposits, which have been overlooked for the 

 reason that the fishers, not finding any in the shoal water 

 had not thought to look elsewhere. The shallow water at 

 these places is skirted by sandy bays, in the neighbour- 

 hood of which (as before stated) this mollusc cannot live. 

 Again, where the lagoons run into great bights, where there 

 is no perceptible current, the shoal water is too hot for 

 them ; although in the deep hollows they exceedingly 

 abound, but in such manner that they are not easy to be 

 seen, unless a man goes down purposely to look for them. 

 Pearl oysters are like sponges certain conditions are 

 necessary to their development ; whereas, in other localities 

 presenting apparently the same natural aspects, they are 

 not found at all. * 



The fishery for mother-of-pearl shells in Western Aus- 

 tralia is prosecuted on the north-west coast, about 1300 

 miles from Fremantle ; vessels ranging from five ton cutters 

 to large schooners are engaged in it, the work being carried 

 on by native and Malay divers. The natives are very 

 expert at diving, but cannot be depended on to remain 

 steadily at work, and though the Malays have to be paid 

 better wages they are found more profitable and far less 

 trouble. The shells average about one pound each, and 

 are worth 7 to 8 the cwt. ; so that on a good bank 



* H. B. Sterndale in Journal of Applied Science, 



