Earths

(ürthz.) (Chem.) A name given to those solid bodies composing the mineral strata, which are inconibustible, colorle , not convertible into metals by any ordinary methods of reduction, and, when reduced by scientific experiments, po e ing generally but an evanescent metallic existence. They were regarded as elementary bodies until the brilliant researches of Sir H. Davy proved them to be compounds of oxygen with peculiar bases. They are tastele , inodorous, uninflammable substances, usually occurring in intimate union with each other, with various acids, and with oxides of the common metals. Under these circumstances, they constitute by far the greatest part of the strata, gravel, and soil, forming the mountains, plains, and valleys of our globe. Their number is ten. Five of them po e decided alkaline properties-baryta, strontia, lime (cal cia), magnesia, and lithia. Five of them are termedE. proper-alumina, glucina, yttria, zirconia, and tho rin a; these do not change the infusion of cabbage or tincture of litmus, do not readily neutralize acidity, and are insoluble in water. [s. 312]