The natural bodies whence metals are extracted. Metallic substances, when found pure, are called native; but when combined with other substances, as they generally are, they are denominated ores. As it is of the utmost importance to be acquainted with the materials of which ores are composed, as well as the simplest and easiest processes by which they may be separated from each other, we deem it necessary to give the following brief account of the modes of reduction usually adopted.