It is a late echo of the scriptural saying, "Cast not your pearls before swine." No modern poet shows more knowledge of the nature, or a more just appreciation of the delicate beauty of the gem than Emerson. In his "May Day," speaking of the tardiness of the spring, he writes: "Slow grows the palm, too slow the pearl." Evidently he knew of the slow process by which the successive coats of filmy nacre increase the size of the growing gem. Likewise a couplet in "Nature" betrays the poet's observation of the iridescent nature of the colors in mother-of-pearl, and in the gem occasionally when those fleeting tints are added to the beauty of its luster; the lines are a dainty illustration: Illusions like the tints of pearl, Or changing colors of the sky. Some of the great poets, notably Tennyson, apparently confuse the gem with its mother-of-pearl, or refer to the latter only when they speak of pearl. In his "Recollections of the Arabian Nights," however, Tennyson in describing one of his beauties evidently refers to the gem: And a brow of pearl Tressed with redolent ebony. Writing of the mermaid, the lines are more suggestive of the shell nacre: Combing her hair Under the sea, In a golden curl With a comb of pearl. Again in a sonnet, he evidently refers to mother-of-pearl when he says: All night through archways of the bridgèd pearl, And portals of pure silver, walks the moon. This indiscriminate use of the gem's name to appropriate its pearly characteristics is a common poetic license. In Ben Jonson's "Hymn to Diana," he bids her, Lay thy bow of pearl apart. Sometimes metaphor is worse mixed, as when Milton in "Paradise Lost" describes the waters above the firmament about the gate of Heaven thus: And underneath a bright sea flowed Of jasper, or of liquid pearl. In this poem of gorgeous description, the author makes several allusions to the gem and some of them, especially those in his word paintings of scenes in Eden, are poetically beautiful and true. One delightful to the eye of the mind, How from that sapphire fount the crispèd brooks Rolling on orient pearls and sands of gold, and another in the description of morning in Eden, equally beautiful though it takes more license: Now Morn, her rosy steps in th' eastern clime Advancing, sow'd the earth with orient pearl. In his "Epitaph on the Marchioness of Winchester," a couplet shows that he was familiar with the superstition of sorrow connected with them: And those pearls of dew she wears, Proove to be presaging tears. Herrick also associated pearls and tears though more happily as in "Corinna's Maying." Besides, the childhood of the day has kept, Against you come, some orient pearls unwept. The same poet makes charming reference to pearls in his poem entitled: "To Daffodils." Or as the pearls of morning dew Ne'er to be found again.