382 The Commercial Products of the Sea. 



and inventive genius are being constantly devoted to its 

 utilization. 



We may now turn to a few details of the commerce in 

 pearl shells. It was only in 1853 that mother-of-pearl 

 shells were deemed of sufficient importance to appear in 

 the Board of Trade returns. The imports from that period 

 to 1870 were as follows. No official returns have, however, 

 been published since : — 



In the time of the Jesuit missionaries the pearl fishery 

 was actively carried on, and produced great wealth to the 

 people of Lower Cahfornia. The value of the shells is 

 sufficient to pay the expense of the fishing, leaving the 

 pearls which may be obtained as clear gain. The best 

 pearl-bearing shells are found at between 14 and 18 

 fathoms, but locality has, apparently, much influence both 

 on the shell and the pearl, not only in quantity but also 

 in quality. At some of the islands, the banks, even in 

 shallow water, are quite choice in their yield, while at 

 others, as in the Isle de Puercos, the shells are tortuous 



