The details of Linnæus’s “secret” have never been published authoritatively. In his “History of Inventions,” Beckmann states that before the naturalist thought of the profits that might accrue from his discovery, he intimated the process in the sixth edition of his “Systema naturæ,” wherein he states: “Margarita testæ excrescentia latere interiore, dum exterius latus perforatur.”[328] “I once told him,” says Beckmann, “that I had discovered his secret in his own writings; he seemed to be displeased, made no inquiry as to the passage, and changed the discourse.”[329] In the second volume of his edition of “Linnæus’s Correspondence,”[330] Sir J. E. Smith remarks: “Specimens of pearls so produced by art in the _Mya margaritifera_ are in the Linnean cabinet. The shell appears to have been pierced by flexible wires, the ends of which perhaps remain therein.” Referring to this remark, J. P. Bagge comments: “This is the nearest I have seen any one come to truth, but still it will be remarked by reading the ‘secret’ that more information is required to enable persons to practice the art.” After a thorough examination of the manuscripts and other material, Professor Herdman concludes that the essential points of Linnæus’s process are to make a very small hole in the shell and insert a round pellet of limestone fixed at the end of a fine silver wire, the hole being near the end of the shell so as to interfere only slightly with the mollusk, and the nucleus being kept free from the interior of the shell so that the resulting pearl may not become adherent to it by a deposit of nacre.[331] Shortly after Linnæus communicated with the Swedish government and before his death, it was learned in Europe that the art of producing “culture pearls” by a somewhat similar process had been practised by the Chinese for centuries.[332] They used several forms of matrices or nuclei, but principally spheres of nacre and bits of flat metal or molded lead, which were not infrequently in conventional outline of Buddha. In the spring or early summer, these were introduced under the mantle of the living mollusk after the shell had been carefully opened a fraction of an inch, and the animal was then returned to the pond, or lake. The mollusk did its work in a leisurely way, like some people who have little to do, and many months elapsed before it was ready for opening and the removal of the pearly objects. The most satisfactory description we have seen of this process appears to be that communicated nearly a century later to the London Society of Arts by Dr. D. T. Macgowan,[333] through H. B. M. plenipotentiary in China, from which this account is abridged and modified.