MOTHER-OF-PEARL AND BLISTER PEARLS 



129 



small cutters. In that year the total production of pearl shell {Trochus shells not 

 included) was 803 tons, worth about $2500 per ton. 



In the Queensland fisheries all shells are inspected by a government official 

 before exportation and no shell measuring less than 5 inches across the nacreous 

 surface is permitted to be exported. The pearl fishery is conducted solely for the 

 raising of mother-of-pearl shell, not for the beautiful gems the shells sometimes 



{Courtesy Co»imonzfcalth Fisi.H'ics l'^':i'c) 



Fig. 8-1. Type of pearling vessel at Thursday Island. 



contain. It is remarkable that, in spite of the large quantity of shells recovered, 

 fewer pearls occur in the Queensland shells than in those from other fisheries. 



In the early days of the Austrahan fishery shell was picked from the bottom of 

 shallow waters by naked divers, but as the industry expanded, competition forced 

 the exploitation of new off-shore beds, thus necessitating the introduction of the 

 diving dress, mechanical air pump, larger vessels, and more costly apparatus. 

 Although Europeans successfully undertook the work of deep-diving, they were 

 gradually displaced by Asiatic divers. 



Since the end of World War I diving equipment has been materially improved 

 with a consequent lessening of risks. The introduction of the British Admiralty's 

 methods of "staging"— allowing the diver to remain for periods at certain depths 

 on his final ascent of the day so that his body may become adjusted to pressure 

 di£Ferences— has proved a satisfactory preventive for the dreaded diver's paralysis, 

 or "bends," which has claimed hundreds of victims during the brief history of 

 the fishery. Another innovation for lessening the fatigue of divers has been the 

 practice of towing the diver just oflE sea bottom until a patch of shell is located. 

 The diving suit and the methods used in diving are much the same as those used 

 in fishing for sponges. 



Society Island Fisheries. A considerable quantity of mother-of-pearl shell is 

 exported from Tahiti, Society Islands to the United States. The beds give no in- 

 dication of approaching exhaustion, and the fishing is carefully safeguarded by 

 the colonial government. As a rule the native divers and shellfishermen have to 



