Romè de L’Isle was the first mineralogical writer who classed the gems systematically; but it has since appeared that the amateur, Chevalier Baillou, preceded him in his crystallogical ideas; for in 1747 this observer described, in the catalogue of his collection, his views in relation to the properties of gems, and how their characters might be readily ascertained by the tests of hardness and specific gravity, and also by the form of their crystallizations. The distinguished and learned Abbé Haüy became interested and even fascinated with the study of the history and physical properties of the gems and the precious stones; and to his genius we are indebted for much of the information we have at the present day on this subject. He was deeply interested in the nature and characteristics of the Oriental precious stones; and being dissatisfied with the harsh term and the vague synonomy of “korund,” as applied to some of them, he proposed the more elegant name, “telesie.” But science, often disdainful of new terms, finally adopted the name proposed by Wallerius; and at the present time all of the fine and transparent varieties of corundum are called sapphire. This remarkable mineral is found in mineralogical specimens in China, Siberia, America, and other parts of the world; but all of the fine gems, with perhaps few exceptions, come from Burmah, Pegu, Siam, lower Bengal, and Ceylon. The island of Ceylon is the most famous of all the localities thus far known, and it is in reality the most wonderful gem deposit in the world. It was known in the period of the Roman Empire, as the land of the luminous carbuncle. This island, which is situated at the southeast extremity of the peninsula of Bengal, and separated from it by a broad but shallow strait, is about as large as England in its area. In the southern centre of the island a group of lofty mountains appears, rising to the height of about 8,000 feet above the level of the sea. On one side this great upheaval descends in successive ranges of hills until the flanks of the mountains subside into the alluvial plains; whilst on the other side the mountain range is characterized by abrupt precipices sometimes of several thousand feet in height. The great gem-producing districts of the island extend along the base of this mountain range for about fifty miles; and the central and richest part is considered to be located around Ratnapoora, which is scarcely two hundred feet above the level of the sea. This want of elevation in the Ceylon gem strata or placers becomes a marked feature when considering the high plateaux in which the diamond occurs in other parts of the world, also coupled with the fact that the two gems are not found together in the same placers. Here are situated the celebrated mines which have yielded vast quantities of the sapphire, especially the blue variety, for an indefinite period of time. They are not small and trivial deposits, but extend over large areas.