CALCAREOUS 285 CALCIUM CALCAREOUS, a term applied to sub- stances partaking of the nature of lime, or containing quantities of lime. Thus we speak of calcareous waters, calcare- ous rocks, calcareous soils. Calcareous spar, crystallized carbonate of lime. It is found crystallized in more than 700 different forms, all having for their primitive form an obtuse rhomboid. The rarest and most beautiful crystals are found in Derbyshire, England. CALCAREOUS TUFA, a deposition from springs, streams, or underground water, from which it is precipitated partly by the escape of carbonic acid which acts as a solvent, and partly by evaporation of the water. It is usually white, creamy-white, yellowish, or brownish in color, but other hues occur, and variegated and mottled varieties are not uncommon. It is of variable texture and consistency; some kinds being rather soft, brittle, and friable, and porous or cellular. These cellular vari- eties have been deposited from the waters of springs, and often contain vegetable and animal remains, as leaves, twigs, nuts, moss, insects, land and fresh-water shells, etc. The so-called "petrifying springs" of Matlock afford a good example of the formation of cal- careous tufa. In some regions the depo- sition from calcareous waters is on a very extensive scale, as along the river Anio, at Tivoli, near Rome, where cal- careous tufa occurs in masses many feet in thickness. In that district the forma- tion is harder and more compact, and under the name of travertino is used as a building stone at Rome. Calcareous tufa is abundantly deposited from thermal springs, as in the Yellowstone region of the United States. The cal- careous incrustations so commonly seen in caverns in limestone rocks are varie- ties of calcareous tufa. They are known as stalactites and stalagmites. CALCEOLARIA, a well known and beautiful genus of plants — order Scropfi- ulariacess. The resemblance to a shoe is in the bilabiate corolla of the best known species, the elongated lower lip of which is inflated and turned down. The stamens are only two. The species, which are numerous, come from South America, chiefly from the western slope or side of the Andes. The greater num- ber have yellow flowers, others are pur- ple, while in a few the two colors are intermingled. The roots of Calceolaria arachnoida are collected in Chile, where they are called relbun, and are used for dyeing woolen cloth crimson. Various calceolarias are cultivated in the United States. 19— Vol. II— Cyo CALCHAS (kal'kas), a celebrated soothsayer, son of Thestor, lived in the 12th century B. C. He accompanied the Greeks to Troy, in the office of high priest, and prophesied the principal events which were destined to take place regarding that doomed city. He had re- ceived the power of divination from Apollo, and was informed that as soon as he found a man more skilled than himself, he must perish. This happened near Colophon, after the Trojan war. He was unable to tell how many figs were on the branches of a certain tree; and when Mopsus mentioned the exact number, Calchas died through grief. CALCIFEROUS EPOCH, one of the subordinate divisions of the Lower Si- lurian System of North America. The division is characterized by the presence of calcareous sandstones and limestones. In Scotland a subdivision of the Carbon- iferous system is known as the Calcifer- ous Sandstone group. CALCITE, CALCAREOUS SPAR, or CALC-SPAR, the name usually given by minerologists to carbonate of lime, rhom- bohedral in its crystallization. It dif- fers from aragonite only in crystalliza- tion. Calcite is one of the commonest minerals. Marble, for example, is com- posed of small crystalline granules of this mineral. It is abundantly met with in very many rocks as a secondary min- eral ; that is to say, it is a decomposition product — the result of the chemical al- teration of various rock-constituents, such as the feldspars. Thus it frequently occurs in the cracks, fissures, and ves- icles of igneous rocks. The name Ice- land spar has often been given to cal- cite, at least to the finest colorless and transparent variety, because it is found in Iceland, filling up clefts and cavities in the basalt-rocks of that region. Slate spar is a lamellar variety, often with a shining, pearly luster and a greasy feel, and is found in Wicklow in Ireland, Glen Tilt in Scotland, and Kongsberg in Nor- way. CALCIUM, a dyad metallic element. Symbol, Ca; at. wt., 40; sp. gr., 1.57; obtained by Davy by decomposing the chloride by electricity; also by heating the iodide with sodium in a closed vessel. Calcium is a yellowish white, ductile, malleable metal, which oxidizes in damp air; it decomposes water, and dissolves easily in dilute acidb^ Heated in the air, it melts at red heat, and burns with a bright orange-red light. Calcium oc- curs in nature chiefly as a carbonate, silicate, and sulphate. Calcium oxide, CaO, called also lime, is obtained by heating the carbonate of calcium to red*
