and then subjecting the surface to the action of hydrofluoric acid. This was the invention of Janin, Jacquin, or Jalquin, a rosary-maker in Paris, in 1680. A thousand fish yield less than an ounce of the "pearl essence" which is correspondingly costly. The cheaper so-called Roman pearls have a lustrous coating on the outside, but bear little resemblance to real pearls, or even to the artificial pearls just described.
Considering the vast values in gem pearls obtained from the Eastern fisheries, it is surprising to find that the plain, unromantic mother-of-pearl secured is of even greater worth. Previous to the discovery of the extensive Australian fishing grounds, in 1865, the supply of mother-of-pearl was diminishing, while the demand was increasing. The large-shelled species already mentioned are there found in fine quality. The shells are the size of large soup-plates, weigh a pound each, and are worth about a dollar a pair. An expert diver, in diving dress, will collect three or four hundred pairs in a day. About a hundred gem pearls are found in every ton of these shells.
Beautiful art work in carved and inlaid mother-of-pearl has long been produced in China and Japan. Some idea of the extent of its European use in the arts and manufactures may be had from the fact that eight thousand people are engaged in working mother-of-pearl in Austria, and half that number in France, while the value of the annual import into England is nearly one and a half millions. In the Philippine Islands windows are made of mother-of-pearl; and James Anthony Froude, in his volume of voyaging in Oceana, describes frightful Maori idols with slips of mother-of-pearl glittering in their eye-sockets; while in Cashmere it is the custom to inlay the inscriptions in tombstones with the same exquisite substance. To cap the climax of curious uses of the lustrous nacre, it is said that large quantities of seed pearls are imported into China to be calcined into medicines for the Celestials.
