The earth which has been gathered up for washing, if it is not worked immediately, is placed under a long shed, and when the rainy season begins, and water becomes abundant, the slaves are assembled for their duty. In the diamond district of Brazil the sheds are generally about thirty yards long, and half as wide. They consist simply of upright posts, and a thatched roof, erected over the spot where the heaps of gravel are placed. A stream of water is conducted through this shed. There is a range of sloping troughs, each about three feet wide, connecting with the streams at the upper end. Opposite the troughs there are high chairs, where the overseers are stationed. A slave at each trough takes about a bushel or so of the gravel, and lets the water in slowly, in order to wash away the gravel and earthy particles. Then he throws out the largest stones, and examines the rest, with great care, for diamonds. Whenever he finds one, he stands upright, clasps his hands, holding the stone between his thumb and finger, and shows it to the overseer, who receives it. When a slave finds a stone exceeding seventeen and a half carats in weight, he is immediately set at liberty. Free papers are given him, and he cannot again be enslaved. Generally, on such occasions, a holiday or half-holiday is granted to the negroes about the establishment. The lucky finder is carried on the shoulders of his comrades, and when the day ends most of them are in a condition the reverse of sober. [Sidenote: DISCOVERY IN BRAZIL.] In the diamond district of Brazil the diamonds were first discovered by gold miners, about the year 1730. At first they were ignorant of the value of the gems, and threw them away as useless. Some of the stones were sent to the governor of Brazil as curiosities. He supposed that they were crystals, and by accident a few were carried to Lisbon, where they happened to be shown to the Dutch consul. The consul was a diamond sharp, and recognized the true character of the stones. He immediately caused them to be sent to Holland, where they were cut, and found to be of great value. As soon as the character of the stone became generally known, large quantities of them were gathered and sent from Brazil, and at one time it seemed as if the diamond market would be ruined. The Portuguese government took means to secure a monopoly of the trade. The diamond district was surrounded by well-defined boundaries, which were guarded with the greatest care. No one was permitted to cross them without a permit from the superintendent of the mine, and whenever a traveller who had visited the diamond ground was leaving it, he was obliged to submit to a thorough examination of himself and baggage. So great was the vigilance, that, it is said, at one time every traveller leaving the district was detained three days at the boundary, and was compelled to swallow medicines whose effect was to prevent his absconding with any precious stones concealed in his stomach.