§142. Private Slaves.--Private slaves either were employed in the personal service of their master and his family or were kept for gain. The former, known as the _familia urbana_, will be described later. The latter may be classified according as they were kept for hire or employed in the business enterprises of their master. Of these last the most important as well as the oldest (§129) class was that of the farm laborers (_familia rustica_). Of the others, engaged in all sorts of industries, it may be remarked that it was considered more honorable for a master to employ his slaves in enterprises of his own than to hire them out to others. At the same time slaves could always be hired for any desired purpose in Rome or any other city.
§143. Industrial Employment.--It must be remembered that there were practically no freeborn laborers left in the last century of the Republic (§129), and that much work was then done by hand that is now done by machinery. In work of this sort were employed armies of slaves fit only for unskilled labor: porters for the transportation of materials and merchandise, stevedores for the lading and discharging of vessels, men who handled the spade, pickax, and crowbar, men of great physical strength but of little else to make them worth their keep. Above these came artisans, mechanics, and skilled workmen of every kind: smiths, carpenters, bricklayers, masons, seamen, etc. The merchants and shopkeepers required assistants, and so did the millers and bakers, the dealers in wool and leather, the keepers of lodging houses and restaurants, all who helped to supply the countless wants of a great city. Even the professions, as we should call them, were largely in the hands of slaves. Books were multiplied by slaves. The artists who carved wood and stone, designed furniture, laid mosaics, painted pictures, and decorated the walls and ceilings of public and private buildings were slaves. So were the musicians and the acrobats, actors and gladiators who amused the people at the public games. So too, as we have seen (§121), were many of the teachers in the schools, and physicians were usually slaves.
§144. And slaves did not merely perform these various functions under the direction of their master or of the employer to whom he had hired them for the time. Many of them were themselves captains of industry. When a slave showed executive ability as well as technical knowledge, it was common enough for his master to furnish him with the necessary capital to carry on independently the business or profession which he understood. In this way slaves were often the managers of estates, of banks, of commercial enterprises, though these might take them far beyond the reach of their masters' observation, even into foreign countries. Sometimes such a slave was expected to pay the master annually a fixed sum out of the proceeds of the business; sometimes he was allowed to keep for himself a certain share of the profits; sometimes he was merely required to repay the sum advanced with interest from the time he had received it. In all cases, however, his industry and intelligence were stimulated by the hope of acquiring sufficient means from the venture to purchase his freedom and eventually make the business his own.