FORE:In planing and turning, the tools require no exact form; they can be roughly made, except the edge, and even this, in most cases, is shaped by the eye. Such tools are maintained at a trifling expense, and the destruction of an edge is a matter of no consequence. The form, temper, and strength can be continually adapted to the varying conditions of the work and the hardness of material. The line of division between planing and milling is fixed by two circumstancesthe hardness and uniformity of the material to be cut, and the importance of duplication. Brass, clean iron, soft steel, or any homogeneous metal not hard enough to cause risk to the tools, can be milled at less expense than planed, provided there is enough work of a uniform character to justify the expense of milling tools. Cutting the teeth of wheels is an example where milling is profitable, but not to the extent generally supposed. In the manufacture of small arms, sewing machines, clocks, and especially watches, where there is a constant and exact duplication of parts, milling is indispensable. Such manufactures are in some cases founded on milling operations, as will be pointed out in another chapter.As a last illustration of the extent to which authority and subordination were pushed in Roman society, it may be mentioned that the better class of slaves were permitted to keep slaves for their own service. But whether the institution of slavery as a whole should be reckoned among the conditions favourable to authoritative beliefs is doubtful, as it was an element common to every period of antiquity. Perhaps, however paradoxical such an assertion may seem, the very frequency of emancipation gave increased strength to the feeling of dependence on an overruling personal power. A freedman could not forget that the most important event in his life was due, not to any natural law, but to the will or the caprice of a master; and this reflection must have confirmed his faith in the divine beings of whom he and his master were fellow-slaves.
