PEARLS AND IMITATION PEARLS 105 



Each raft supports sixty cages containing a total 

 of about seven thousand pearl oysters. The oysters 

 are carefully guarded, and the water in which they 

 are grown is examined often. Sudden changes in 

 temperature are very destructive to the young melea- 

 grina ; and if for any reason the temperature of the 

 section of the bay where the cages are anchored 

 changes suddenly, the rafts are shifted to a more 

 favorable location. The water must also be examined 

 often to determine whether or not it contains suffi- 

 cient of the marine fauna on which the oysters feed. 

 If the water is found deficient in nourishment, the 

 rafts are towed to a more desirable place. 



Evaluation of Pearls 



Pearls are graded much more closely and critically 

 to-day than they formerly were. The business is now 

 well organized, and much of the sentiment and super- 

 stition of the trade has disappeared. For these 

 reasons it is difficult to compare prices of pearls 

 in ancient times with those of to-day. For while per- 

 fectly spherical pearls of high quality command 

 higher prices than ever before, imperfect ones are 

 difficult to sell at any price. Large irregularly shaped 

 pearls which were valued highly when Roman glory 

 was at its height would attract little notice now. 



The value of a pearl depends upon its shape, size, 

 color, luster, and perfection; consequently, since 

 it is exceedingly difficult to find two pearls exactly 

 alike, it is very hard to formulate rules for the 

 evaluation of pearls. Large spherical pearls are 

 worth much more than small ones, the value increas- 



