This discovery establishes the fact beyond a doubt that the gem occurs in quite perfect form in the territories of the United States. Most of the specimens we have seen were collected at El Dorado Bar, which has since been abandoned by the gold-seekers. From this superficial search and incomplete information concerning the locality of the gem, we are unable to determine whether regular gem mines are to be found in this country, or along the slope of the mountains, which extend either north or south to a great distance. We have been assured, however, by officers of the army, that fine sapphires have been brought to them by the Indians in Colorado living on the same range and formation that stretches into Montana. Therefore we shall not be surprised if well-directed search along this formation should reveal gem beds of value; and the mere circumstance that the gold-washers do not discover them is of but little weight; for gem-seeking and gold-mining are two different explorations. It is a little singular that none of the beautiful gems occur in huge specimens, like some of the products of the vegetable kingdom. Nature, however, in the mineral line, or certainly with the gems, creates her perfections in small bodies. We sometimes find a clear crystal of topaz, tourmaline, or emerald of a few ounces or even pounds in weight, but they are very rare; while the generality of all the choice specimens are comparatively of a diminutive size. When occurring above a certain weight they become defective either in color, limpidity, or form. They are precious stones, it is true, so far as composition is concerned, but they are not gems according to the acceptance of the word. By the word gem we not only mean a precious stone, but its transformation into a form possessing limpidity, brilliancy, attractive color, or some other charm. As regards the sapphire, its perfect forms occur in diminutive size. This mineral is also found in Bohemia, near Merowitz, in an argillaceous or marly cement, with garnets, zircons, and even fossil shells. Tavernier relates that he saw in possession of General Wallenstein, when at Prague, some beautiful rubies, which were obtained in Bohemia. Fine stones of even five karats weight have been discovered at these mines. Concerning the mines of Lower Bengal we have but little information, and will not venture to give a description. We think they have the same characteristics as those of the gem beds of Ceylon. The Ilmenes Mountains, in Siberia, furnish sapphires of a strong blue. In Greece and Saxony they are also found in small quantities of undecided colors, and generally opaque. Impure specimens of well-defined colors are found in the volcanic _débris_ of Expailly, in France, or among the snow-white dolomites of St. Gothard; in the granite ledges close to the base of the glacier of Bois, in the Alps of Savoy, we may observe regular prisms of sapphire, quite transparent and sometimes of a decided blue or a tender green.