GENERAL PROPERTIES OF METALS.

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increased, either in length or breadth, without being liable tofracture. This capacity is not precisely the same in those metalswhich do possess it, for some, which admit of extension whenstruck with a hammer, cannot be drawn into wire, which pro-perty is termed ductility : this property depends in some mea-sure on another peculiar quality of metals, namely tenacity ; bywhich is meant the power which a metallic wire of a given dia-meter has of resisting the action of a weight suspended from itsextremity. All metals are fusible, though the degree of tem-perature at which this can be effected differs very much. Mer-cury is always fluid at the ordinary temperature of our atmos-phere, while platina can scarcely be melted by the most intenseheat of our furnaces. Metals are perfectly opaque when in a stateof fusion ; and are crystallizable when suffered to cool slowlyand undisturbed. The tetrahedron and the cube are theirprimitive figures, though they very often take the octahedralform. They can likewise be volatilized at very high temperatures.They are the best conductors of caloric and electricity. Theirsusceptibility of combination is very great: they unite withcarbon, sulphur, and phosphorus. They do not combine withearths by fusion ; but their oxids readily unite to acids, alcaliesand earths. They decompose water and several acids. Someeffect this at common temperatures : some require a red-heat,and others the interposition of another body. Water does notdissolve any of the metals, though it is a solvent of some of theiroxids. They are insoluble in ardent spirit, ether, or oils. Theyare all capable of combining with oxigen, though many of them,require very high temperatures to effect this union, and otherscannot be united to it but in an indirect manner. Most of themetals can be combined with each other; they then form alloys,many of which are of the greatest utility in the arts.