It is impossible to over-estimate the effect of color in determining the supposed influence of gems upon the fortunes or health of the wearers. When we gaze upon the beautiful play of light emitted by a fine ruby or sapphire, we are all conscious of the æsthetic effect produced; but in earlier times, when scientific ideas were not yet prevalent, many other considerations combined to give a peculiar significance to these brilliant gems. Rare and costly as they were, they were supposed to possess mystic and occult powers and were thought to be the abode of spirits, sometimes benevolent and sometimes malevolent, but always endowed with the power to influence human destinies for weal or woe. Coupled with this was the instinctive appreciation of the essential qualities of certain rays of light, and modern science, far from doing away with these ideas, has rather seemed to find a good reason for them. We all know the therapeutic value of the ultra-violet rays, and when the uninstructed mind saw therein the embodiment of purity and chastity, it perhaps realized this health-giving and beneficent function. In the same way the idea of passion was associated with the red and radiant ruby, another concept the relative truth of which has been demonstrated by spectrum analysis, since the red rays are heat-giving and vivifying. But this was not the only source of these primitive ideas in regard to color; the therapeutic effect was often sought and found in some fancied analogy between the color of the gem and the character of the malady or infirmity to be cured. Thus, yellow stones were supposed to be especially efficacious in cases of jaundice, an instance of instinctive homœopathy, based on the dictum _similia similibus curantur_. Following out this train of thought, the red stones were endowed with the power of checking the flow of blood; especially the so-called bloodstone was prescribed for this use, and it was supposed that by its mere touch it could stop the most violent hemorrhages. Green was regarded as the color most beneficial for the sight, and to the emerald and other green stones was ascribed great curative power in this respect. Here, however, the simple influence of the color was later combined with its symbolical significance. In heathen mythology this showed itself in the ascription of the emerald to Venus, as the exponent of the reproductive energies of nature, while in the Christian conception these stones became typical of the resurrection, of the birth into a new and purer life. Nowhere can we find a better illustration of the transforming effect of distinct and diametrically opposite concepts upon the impressions made by natural objects. The pure and colorless and yet brilliant stones, such as the diamond and all other white stones, were naturally brought into connection with the moon, although the diamond, because of its superior qualities and exceptional brilliance and value, was frequently looked upon as the gem of the sun.