LUBRICATION. An object which slides or rolls upon an other generates friction. Unless a solid or a liquid lubricant is placed between the surfaces to hold them apart and allow them to slide on each other with minimum effort, friction ultimately causes abrasion and the destruction of the objects. In nature, the framework of animals comprises many joints which are so perfect mechanically and so well lubricated with a liquid lubricant that they operate for an entire lifetime with an effectiveness that has never been approached in man-made mechanisms. This is due to the suitability of the lubricant provided, which is kept pure and is not allowed to become contaminated. Nature furnishes the greasy lubricant needed to prevent the hair on all animals from cracking and breaking on account of wear, which would thus destroy its usefulness for protection and adornment. Nature does not use the same lubricant for the eyelids as for other parts of the body; she wisely selects and then properly applies what is suitable for each condition of use.
In machines made of parts that move upon each other, lubrica tion is a necessity; otherwise, the operation could not be con tinued without destruction of the parts. The degree of lubrication required is entirely dependent upon the degree of development of the machine.
In ancient times, the machinery that was needed for the lifting of water or of weights, or for the conveying of loads, consisted of simple pulleys, windlasses and the sleds which afterward were developed and became carts and wagons equipped with wheels and axles. These appliances were made of wood. The bearings were rough and, if lubricated at all, in all probability they were packed with fat taken from the bodies of animals. That lubrica tion was understood to the degree that certain mechanical con ditions require heavy lubricants, while others need lighter-bodied oils, is shown by the following incidents.
The chariot found in the tomb of Yuaa and Thuiu. about 1400 B.C., still had some of the original lubricant on the axle. This was analyzed by Lucas, the official chemist of the Cairo museum, and was described in a report on this tomb by Quibell in Catalogue General des Antiquites egyptiennes du Musee du Cairo. The
sample was small, its total weight being 0.59 of a grain. It con tained road dirt such as quartz sand, compounds of aluminium, iron and lime. The lubricant was sticky and slightly greasy. It had a melting point of 49.5° C (I 2 ° F), which suggests its hav ing been mutton or beef tallow, either of which would have proved suitable for axle lubrication in such a warm country.
According to a list prepared by Pliny (A.D. 23-79), the "ancients" of his time had available and in use for various pur poses the oils from about the same number and kind of seeds and plants as we have at present. They were also well acquainted with several products from petroleum and had available the fats and oils from animals. Primitive forms of machinery always have been lubricated with occasional applications of whatever lubricant was available, and conditions in this respect have not changed materially since the first simple machines were made.
For many centuries after the beginning of the Christian era these conditions prevailed.