Of this indirect labor there are several kinds. (1) Those who provide the materials, and there may be many grades of these; (2) those who furnish the implements and the machinery; (3) those who supply the sustenance and shelter, and raiment for the laborers; (4) the government agencies for protecting the workman; (5) organizers and managers of business enterprises, without whom production would often fall far short of what it now accomplishes; (6) the labor of raising children who are subsequently to become laborers; (7) all those engaged in the work of education, by which men are prepared for the most efficient work—this includes not only teachers, but writers, clergymen, etc.; (8) professional men, who devote themselves to matters essential to the interests of the community and thus not only save the time of the laborers, but often their property and their health, and their lives; (9) inventors and discoverers, who ascertain new conditions of more efficient production. These are the principal, though there are also others. READINGS IN ART. I.—SCULPTURE: ITS VARIETIES AND MATERIALS. All work cut out in a solid material, in imitation of natural objects, is called sculpture. Thus carvings in wood, ivory-stone, marble, metal, and works moulded from wax and clay, come under the head of sculpture. But sculpture, as we are about to consider it, is to be distinguished by the term _statuary_ from all carved work belonging to ornamental art and glyptics. It must be borne in mind, however, that the sculptor does not ordinarily carve his work directly out of the marble; he first makes his statue, or bas relief, in clay or wax. This method enables him to “sketch in clay” and perfect his work in this obedient material. Michael Angelo, and many great masters could dispense with this and carve at once the statue from the block. The modeling in clay is, however, generally the primary work. The “model,” as it is called, is afterward moulded, and by means of this mould a cast of the original clay statue, or bas-relief, is taken by the use of liquid plaster. The clay model is, therefore, like the original drawing of a painter—a master work.