In any county where it is clearly more advantageous to the county to work the county convicts or some of them on the public roads of the county, or on other works of the county exclusively public in their character, the board of supervisors shall have the authority so to order, and in such cases the board shall establish all proper regulations for the working, guarding, safekeeping, clothing, housing and subsistence of convicts while so working, and shall provide all the necessary equipment for such purpose. The board shall establish regulations for the discipline of convicts on said works, and on county farms, when a convict is persistently idle or refractory, and may enforce such regulations by penalties.