COAHUILA, ko'a-wela (named from the Mex ican tribe Coahuiltecs). A northern State of :Mexico, separated from Texas on the north and east by the Rio Grande, and covering an area of 63,570 square miles (Map: Mexico, II 4). With the exception of the eastern part, which is some what mountainous, the surface forms an eleyated plateau, with a general incline toward the Rio Grande. The western part is taken up by the Bolson de Mapimi, a semi-desert region, only partially explored, with many lagoons and vast mineral resources. The climate is moderate and healthful. The chief occupation is cattle raising, although the soil is well adapted for the growing of cereals and European vegetables, to which more and more attention is being paid. In the southwest some vines and cotton are cultivated. The State is traversed from north types being connected by all degrees of inter mediate stages. In Carboniferous times certain
regions were covered by rank and luxuriant vege tation which grew upon swampy land slightly raised above the level of the sea. As the plants died, their remains fell into the water of the swamp, and slowly formed an accumulation of vegetable matter of increasing thickness. By slow subsidence this thick layer of vegetable mat ter sank below the water, and became gradually covered by sand, mud, or other mineral sedi ments, washed out from the shore. Successive elevations and depressions, with intervening ac cumulations, may thus have yielded successive beds. Subsequent elevation, folding of the earth's crust, and accompanying metamorphism, followed by erosion of the surface, has exposed to view the edges of the once deeply buried beds of coal.