The use of green stones to relieve diseases of the eye was evidently suggested by the beneficial influence exerted by this color upon the sight. The verdant emerald represented the beautiful green fields, upon which the tired eye rests so willingly, and which exert such a soothing influence upon the sight when it has been unduly strained or fatigued. One of the earliest, probably the very earliest reference in Greek writings to the therapeutic value of gems, appears in the works of Theophrastus, who wrote in the third century before Christ. Here we are told of the beneficial effect exercised by the emerald upon the eyes. [Illustration: 1. Necklace of carnelian beads. Persian. The decoration is made with carbonate of lime and fixed by firing. Charms against the Evil Eye. 2. Necklace of onyx beads. Early Christian.] The sapphire, the lapis-lazuli, and other blue stones, with a hue resembling the blue of the heavens, were believed to exert a tonic influence, and were supposed to counteract the wiles of the spirits of darkness and procure the aid and favor of the spirits of light and wisdom. These gems were usually looked upon as emblems of chastity, and for this reason the sapphire came to be regarded as especially appropriate for use in ecclesiastical rings. Among purple stones, the amethyst is particularly noteworthy. The well-known belief that this gem counteracted the effects of undue indulgence in intoxicating beverages is indicated by its name, derived from μεθύω—“to be intoxicated,” and the privative α, the name thus signifying the “sobering” gem. It is not unlikely that a fancied resemblance between the prevailing hue of these stones and that of certain kinds of wine first gave rise to the name and to the idea of the peculiar virtues of the amethyst. We have mentioned only a few of the more obvious analogies suggested by the color of gems, and we might be tempted to cite many others were it not that symbolism is always treacherous ground, since there is practically no limit to the correspondences that may be found between sensuous impressions and ideas.