a word applied to denote that property of some bodies, by which they resist the most violent fire without any sensible alteration. Apurous bodies ought to be distinguished from those which are refractory. Refractory substances are those which cannot by violent heat be fused, whatever other alteration they may sustain. But a body, properly speaking, apurous, can neither be fused by heat, nor can undergo any other change. Diamonds were long thought to be possessed of this property. But some late experiments have shown, that diamonds may be entirely dissipated or evaporated by heat, and are therefore not entitled to be ranked among apurous substances. Perhaps there is no body in nature essentially and rigorously apurous. But it is sufficient that there be bodies apurous relatively to the degree of fire which art can produce, to entitle them to that name.