562 



'■ \os. to \l. i6i. per ounce. We are told that a peatl 

 " had been taken there, that weighed 33 grains. But 

 " this fifhery is at prefent exhaufted, from the avarice of 

 " the undertakers : it once extended as far as Loch-TayJ' 



Thefe Miifcles were doubtlefs the My a Margaritifsra, 

 and it is probable many other rivers in Great Britain 

 might afford at this time a fufficient quantity to repay 

 the experiment. In many of the rivers of Wales, d^s. well 

 as in Devovjjiirc, we have obferved thefe fhells in abun- 

 dance ; but whether they equally produce pearls we can- 

 not determine ; thofe, however, found in the former 

 rivers are ufually more rugged than what are obferved 

 in the latter; a circumllance more favourable to the 

 produftion o{ pearls \ and it is a known faft, that the old, 

 rusrsred, decorticated fliells, are cnlv worth examininsc; 

 the fmooth ones rarely produce any, or fo inferior in 

 fize, as to be of no value. 



In Doftor Pulteney's view of the writings of Lin- 

 N^us, page 42, it is faid, that the Swedijh naturalifh 

 made a remarkable difcovery relating to the generation 

 of pearls, in the x'w^x pearl mufcle. My a Margaritifera. 

 It appears, that five or fix years are requifite, after the 

 operation, to compel them to produce j^^ar/j the fize of 

 a vetch. 



This extraordinary operation the Doflor regrets we 

 are unacquainted with, and which was confidered of fo 



-much 



