In order that all parts of the materiel may function easily, it is necessary that all the working and bearing surfaces may be properly cleaned and lubricated with the appropriate lubricant. Where such surfaces are not directly accessible, oil holes are provided; these holes should be kept free from grit and dirt. Except during oiling, they should be kept fully closed by the means provided. For use in service, for the cleaning and preservation of this materiel, the ordnance department issues hydroline oil, lubricating oil, clock oil, vaseline, sperm oil, coal oil, neat’s-foot oil and light slushing oil. Each of these oils are suited for the particular purpose for which it is issued, as stated below, and care should be taken that it is not used for other purposes. =Hydroline oil.=—Used in the recoil cylinders of the carriage _and for no other purpose_. Never used as a lubricant. It is characterized by its low freezing point and its non-corrosive action on metals. =Lubricating oil= (_Engine oil Number 1_).—A light petroleum oil used exclusively in all oil holes of the materiel, and in lubricating such parts as wheels and axles, guns and cradle slides, cradle pintle and socket elevating and traversing mechanisms, exterior of cylinders, brake bearings, hinges, different surfaces of breechblocks, threads, breech recess, et cetera. =Clock oil.=—Used on the spindle and all gearings of the Battery Commander’s telescope, bearings of the panoramic sight, range quadrants and fuze setters. In all cases clock oil should be used only when the instruments mentioned are disassembled for cleaning. It should be applied by dropping from the end of the dropper attached to the end of the cork. In case of emergency, use as a substitute either sperm oil or Engine oil No. 1, in the order mentioned. =Vaseline= (=Petrolatum=).—The heavy petroleum oil free from rosin. Used on the worm gears and the worm racks of the panoramic sight, the hand and bracket fuze setter, B. C. telescope, and on the micrometer screw and bushing of the quadrant. The spare parts of the breech mechanism should also be coated with vaseline and each piece then wrapped in paper to prevent the oil from being rubbed off. =Sperm oil.=—A lighter lubricant than the lubricating oils, and may be used on the gears of sights, fuze setters, ranges, quadrants, parts of revolvers, et cetera; lubricating oil may also be used on such parts. It is also used as a temporary rust preventive. Its low viscosity and light body make it unsuitable for this purpose for more than a few days. =Coal oil.=—Used for cleaning purposes. In the field it may be used for lanterns. Coal oil for general illuminating purposes is furnished by the quartermaster department. =Neat’s-foot Oil.=—An animal oil used for softening and preserving leather. Applied with a moistened cloth to the flesh side of moistened leather.