By this means, only an insufficient quantity of oil can be caused to flow into the reservoir, as the pressure of the air inside will prevent the oil flowing in; as, in the case of a glass tube with the upper end sealed up, it has been shown (22, 2) that the water refused to be drawn up the tube, even with the added pressure caused by the lower end of the tube being below the water line. Again, the point of pegwood is liable to have minute fibres of wood adhering to it, which will be incorporated with the oil; and its liability to break off, and remain in the jewel hole, is another reason why pegwood should never be used. The author advances a method, which is not open to these objections, as follows: When about to place the cap jewel in position--after the hole jewel is in place if it be in a setting--a small quantity of oil is placed ON THE CAP JEWEL, as shown at O, Fig. 14, _being very careful to allow no oil to spread upon the cap jewel setting_. This setting is then carefully placed in position; when the oil, if the operation has been skillfully performed, is seen to be collected in the reservoir _R_ and _in_ the jewel hole. The appearance which it will assume is shown in Fig. 14. The advantages which this method possesses are: the reservoir can by this means be made to contain the maximum quantity of oil; and the oil cup or sink _S_ is left with its surface dry, thereby exposing less oil to the influences of the air; and, at the same time the tendency of the oil to flow towards the shoulder of the pivot is decreased. Skill is necessary in order to judge of and place the requisite amount of oil on the cap jewel before putting it in position; as, if too much is used it is worse than if too little is employed, because the oil would then flow on to the setting, and from there _between_ the settings at _b_, when it will rapidly be all drawn _from the bearing_, leaving it dry, while the _settings_ are copiously supplied. The approximate relative position which the oil should occupy is shown at _d_, Fig. 14, in section; and this can be seen by looking through the jewels with a double eye-glass, when a true circle, concentric with the jewel hole, will be seen to have formed. This circle represents the limit of the distance which the oil has flowed from the jewel hole. When too much oil has been applied, this limit is not a circle, but represents a U. In the example given, the upper surface of the cap jewel is made flat, while the lower surface is made convex with a flat space in the center; as a better view of the end of the pivot and the condition of the oil can be thereby obtained.