CHAP. 54.—PEARLS; HOW THEY ARE PRODUCED, AND WHERE. The first rank then, and the very highest position among all valuables, belongs to the pearl. It is the Indian Ocean that principally sends them to us: and thus have they, amid those monsters so frightful and so huge which we have already described,[2609] to cross so many seas, and to traverse such lengthened tracts of land, scorched by the ardent rays of a burning sun: and then, too, by the Indians themselves they have to be sought in certain islands, and those but very few in number. The most productive of pearls is the island of Taprobane, and that of Stoïdis, as already mentioned[2610] in the description of the world; Perimula,[2611] also, a promontory of India. But those are most highly valued which are found in the vicinity of Arabia,[2612] in the Persian Gulf, which forms a part of the Red Sea. The origin[2613] and production of the shell-fish is not very different from that of the shell of the oyster. When the genial season of the year[2614] exercises its influence on the animal, it is said that, yawning, as it were, it opens its shell, and so receives a kind of dew, by means of which it becomes impregnated; and that at length it gives birth, after many struggles, to the burden of its shell, in the shape of pearls, which vary according to the quality of the dew. If this has been in a perfectly pure state when it flowed into the shell, then the pearl produced is white and brilliant, but if it was turbid, then the pearl is of a clouded colour also; if the sky should happen to have been lowering when it was generated, the pearl will be of a pallid colour; from all which it is quite evident that the quality of the pearl depends much more upon a calm state of the heavens than of the sea, and hence it is that it contracts a cloudy hue, or a limpid appearance, according to the degree of serenity of the sky in the morning.