“_Searching the wave I won therefrom a pearl Moonlike and glorious, such as kings might buy Emptying their treasury._” ARNOLD. The name “pearl” is derived from the Latin Pilula, diminutive of Pila, a ball, and some of the forms of the word noted are perle, peerle, perl, perll, perill, pearel, peirle, pearle. The pearl is a product of certain salt and fresh water shell-fish of the Aviculidae family. It is formed by the efforts of the mollusc to rid itself of irritating substances by the iridescent fluid secretion with which he lines his shell. The effect of this irritation is shown in a number of irregular tubercules inside the shell, and within these coverings is the securely protected pearl. Frequently pearls of most beautiful lustre and form are found detached from the shell in the fleshy folds of the oyster, and these are said to be the most perfect. It is now quite certain that disease is not the cause, as has so generally been believed. Amongst the ancient writers so much of the purely symbolic was set down in perfectly plain, matter-of-fact language that it is difficult to make assertions as to what was really known of the material truth. Both Pliny and Discorides poetically state that dew or rain from Heaven fell into the open pearl shells and were transformed by the secretions of the oyster into precious pearls. There is an old legend which tells that the tears of joy shed by the angels for the ultimate destiny of man were the tears that fell into the pearl oyster shell to be transformed into beautiful pearls. Moore delightfully refers to this story: “_Precious the tear as that rain from the sky Which turns into pearls as it falls in the sea._” The philosopher Anicius Boethius, of the 5th and 6th centuries, A.D., writes that the fresh water pearl mussels of the Scotch rivers, the sky being clear and the weather temperate, open their mouths just a little above water to catch the heavenly dews, which, when swallowed, cause the breeding of pearls. These mussels, continues the philosopher, are so sensitive that the slightest noise causes them to sink to the bottom of the river. He credits them with “knowing well in what estimation the fruit of their womb is to all people.” Vishnu, according to Indian mythology, created pearls MOTI by his word, and consequently these gems are foremost in the adornment of Indian deities. The Ramayana, perhaps the greatest poem of ancient India, narrates the story of the death of Maha Bali, telling that pearls sprung from the teeth of the slain god. In the winter of 1673 the naturalist Sandius sent—on the authority of “Henricus Arnoldi, an ingenious Dane”—a letter from which the following is extracted to the newly formed Royal Society of London: