CLAVIGE'RO, FRANCESCO SAVERIO, a Mexican historian, was b. in Vera Cruz, South America. about 1720, and entering the order of the Jesuits, was educated as an ecclesi astic. Sent as a missionary among the Indians in various parts of Mexico, he lived among them for 36 years, and made himself fully acquainted with the languages, tra ditions, and antiquities of the aboriginal tribes. On the suppression of the Jesuits in South America by Spain, in 1767, 0. sailed for Italy, and with others of his brethren had the town of Cesena assigned to them by the pope as a place of residence, where he died Oct., 1793. Ile wrote in Italian a History of Mexico, a comprehensive and valuable work, of which an English translation by C. Cullen was published in 1787, in 2 vols. 4to.
CLAY (Ano..-Sax. clay; of the same root as clay, claggy), a term applied, in a vague way, to those kinds of earth or soil which, when moist, have a notable degree of tenacity and plasticity. The clays are not easily distinguishable as mineral species, but they all
appear to owe their origin to the decomposition of other minerals, and to consist chiefly of alumina in combination with silica and with a certain amount of water. See ALUMINA, SHALE, LOAM, PIPE-CLAY. KAOLIN, etc. Common C., when, from the large proportion of alumina which it contains, it is sufficiently plastic, is of great use for making bricks (q.v.), tiles, etc.
C. is used by sculptors and others engaged in the production of works of plastic art, as a means of adjusting the form which is to be given to their work, in the harder or more enduring substance of which it is ultimately to be composed. As modeling C. is apt to crack in drying, it must be kept damp by sprinkling water over it, and covering it with a wet cloth when the artist is not engaged in his work.