The quantity of diamonds afforded by Borneo is not exactly known, but a recent writer in the Journal of the Geographical Society of London gives it as about two thousand karats annually. It is also stated by various authorities that the mines of the island have never yet yielded a diamond of thirty-six karats in weight. If these reports are correct, how can we explain the accounts of the great diamond belonging to the Sultan of Mattan, which may be found in the History of Java, by Sir Stamford Raffles, and also in the Memoirs of the Batavian Society? The famous mines of Brazil, which gave rise to a new era in the commerce and history of diamonds, were discovered by accident. And we are not aware of an instance of the discovery of a single diamond district or region of country, with the exception of the Urals, which can be ascribed to the results of scientific research. Even the wonderfully rich mines of the Province of Bahia in Brazil were first made known by a slave who noticed the similarity of the soil to that of the diamond mines of Minas Geraes, where he had formerly worked. In 1727 a Portuguese by the name of Lobo, while visiting the gold mines of the Sierra do Frio, a desolate country about four hundred miles north of Rio Janeiro, noticed some bright crystals of stone which the ignorant miners picked up from time to time and treasured as trifles. Gathering a number of them, he submitted them to some Dutch traders, who informed him as to their valuable character. The Dutch at once contracted with the Brazilian Government for all of the rough diamonds that might be found, and for a long time controlled the trade. The mines where the gems were first discovered were situated in the midst of a desolate country destitute of vegetation and of considerable elevation above the level of the sea. Since this period other mining districts have been discovered, and it is now ascertained that the whole of the vast territory situated between the twelfth and twentieth parallels of latitude and extending even to Matto Grosso, a thousand miles distant, belongs to the gem-bearing formation.