~60. The Pendant~ is frequently a cause of trouble to the watchmaker. It is very important that the winding stem be lubricated with a substance that will not spread at ordinary temperatures. The lubricant should be applied at all places where steel rubs on steel or other metal. The winding stem and case spring, and the sleeve if present should have as much as can be safely applied; as they are so much exposed that rust often forms, which finds its way down through the movement, frequently resulting in serious damage to the delicate parts. The bearings of collet on stem and the pendant screw should also be lubricated. Attention to these details will also prevent "that squeaking sound" which, sometimes occurring shortly after a watch has been repaired, causes the owner to believe that the work was not done properly. The lubricants just mentioned (59) serve admirably for this purpose. ~61. The Cause of the Cutting of Pivots~, in addition to the effect of friction (32, 1) and other causes which have been mentioned (49), may be that minute currents of static electricity are induced between the surfaces of the pivot and bearing, the oil acting as the electrolyte. If this be the case, the cause of pivots turning black would appear to be explained--the molecules of iron becoming electrically disassociated from the molecules of carbon, the latter being by their nature black, and being now on the surface in sufficient quantities to make themselves evident, give the surface the black color. Such is the first stage of "cutting." The molecules of iron, becoming incorporated in the now thick and viscous oil or imbedding themselves in the bearing, act as an abrasive; the black surface is removed, making the pivot again bright, but "ringed." The molecules of iron, uniting with the molecules of oxygen which exist in the oil in its oxidized state, forms ferric oxide. Ferric oxide is known as colcothar, English-Roth, rouge, crocus, etc. The above theory is advanced by the author for what it may be worth, as it seems to explain this curious phenomenon. FOOTNOTES: [11] Saunier. Watchmakers' Handbook. CHAPTER V. THE PROPERTIES AND RELATIVE VALUES OF LUBRICANTS IN HOROLOGY. ~62. Lubrication~ has for its objects, both the reduction of friction and the prevention of excessive injury from wear; and the mechanician resorts to the expedient of interposing between the rubbing surfaces a substance having the lowest possible coefficient of friction with the greatest possible capacity for preventing wear. The valuable qualities of lubricants are determined by their power of reducing friction, and by their endurance as well as that of the surfaces on which they are used. The amount of frictional resistance to the motion of machinery is obviously determined by the character of the lubricating material.[12]