From the magnificent specimens which the rescued Sindbad carried away with him when he tied himself with his turban to the roc's leg, on through a long succession of fable and of history, diamonds will never cease to enchant mankind, having always taken the lead in interest, as they have been supreme in value among those treasures of the mineral kingdom which are called gems or precious stones. Ages before men discovered that their beauty could be enhanced by handiwork, their rarity and their price had endowed them with a surpassing charm; and now, when handiwork has been brought almost to perfection, and science has dispelled the mystery with which the diamond was invested, they maintain their immemorial supremacy. In company with Mr Streeter we may trace the beautiful things from their habitat in India, the Brazils, South Africa, the Ural Mountains, and Australia, through their history in the ancient times and in medieval days, when they formed the theme of many fables and the object of much superstition. The diamond dwells in the same lands and in the same strata with many other gems, but it is the most precious as it is the most difficult to find; and though its nature resembles theirs in many respects, in one it is unique--it is the hardest of all known substances, and belongs to those bodies which refract light most strongly. Its magnifying power is greater than that of glass; but it is seldom used for microscopic lenses, owing to the great difficulty of making them perfectly accurate. It was believed to possess double refraction, but that has been disproved; and the deviation which gave rise to the error is traced to the existence of internal air-bubbles, as in amber, by which the course of the light is altered. It is the triumph of cutting to exhibit these qualities to the highest degree, and thus did Babinet, a great authority on diamonds, test them. 'In a sheet of white paper he bored a hole somewhat larger than the diamond to be tested: he let a ray of sunlight pass through the hole, and holding the diamond a little distance from it, yet at such an angle as to allow the ray to alight on a point of the flat facet, he found this facet to be forthwith represented on the paper as a white figure, whilst all around little rainbow circles were delineated. If the observer found the primary colours red, yellow, and blue definitely separated one from the other in these little circles, and if their number were considerable, and they stood at equal distances from each other, then he pronounced the brilliant to be well cut.'