8. The diameter of the shoulder S, Fig. 13, is reduced to as small a size as will properly sustain the "end thrust," thus reducing the friction, both solid and fluid, to a minimum, at the same time reducing the distance from the center of the arbor (43, 6) at which the friction acts. 9. The above proportions vary with the nature of the material; where jewels are employed a shorter bearing surface may be used, if it be desired to reduce friction, but the pressure on the oil is the same with jewel as with brass bearings, so that it must not be made so short that the oil will be expelled. ~47. The Shape of Pivots, Shoulders and Bearings~, where the bearings are not capped jewels, should be such as to produce as little friction as possible. They should be hard, symmetrical, and smooth (30). _The construction should be such that a considerable amount of oil may be applied without having a tendency to spread._ The advantages of the construction shown at Fig. 13 are: 1. The oil sink _O_ is deep and narrow, rather than wide and flat--thus causing the oil to be drawn towards the apex of the angle, i. e. towards the pivot, with greater force (22, 5) than if the oil sink were wide and shallow, in which case the oil would have a tendency to spread, as too often occurs. 2. The total length of the pivot is to the length of its bearing surface as 5 is to 3, thus further reducing the angle, which produces a greater tendency (22, 5) in the oil to stay in the oil-sink. 3. A circular groove G is cut around the oil sink, which produces a still greater tendency on the part of the oil to stay in the sink, by removing metal which would otherwise exert an attraction (19) on the oil. 4. The beveled portion P is comparatively large--while the shoulder S is relatively small--thus forming the angle O´ of about 20° with the flat surface of the bearing. This will cause the oil to have a tendency to flow towards the pivot, for the reason given in considering the oil-sink. 5. The boss B is made to diminish the liability of the oil to spread, by a reduction (18-19) of the amount of metal which would otherwise cause it. 6. The back taper T is made for the same reason. Some watchmakers (?) seem to think this is added only for ornament, but it is a very important factor in producing longevity of the oil. 7. The slight chamfer C, in the bearing, serves two purposes; it becomes a reservoir for oil and removes any burr that might otherwise exist in a metal bearing, without in any way altering its effectiveness. 8. It will thus be seen that the oil reservoirs O, O´ and C are made to contain, and retain, the maximum amount of oil, and the supply of the lubricant is thus increased to a maximum length of time. The application of these principles to each part to which they relate will be considered.