~9. Neat's-foot Oil~ is largely used in the arts, being one of the best of lubricants. The best oil, viz.: that used for clocks etc., is extracted by placing the thoroughly cleaned feet of cattle in a covered vessel near the fire or in the sun. The oil thus obtained is clarified by standing before bottling. (67.)
It was the practice of many olden time watchmakers to allow a large bottle of neat's-foot oil to stand in a position exposed to the direct rays of the sun in summer and to the extreme cold of the winter. Then after two or three years, on a very cold winter day, to pour off such oil as still remained fluid which was preserved for use.
~10. Olive Oil~ has been used as a lubricant since the early days of horology, the older writers giving many methods of treating it. It is obtained from the fruit of the _Olea Europea_, one of the jasmines, which grows throughout Southern Europe and Northern Africa and other tropical countries.
[Illustration: _Fig. 2.--A $25,000 Catch of Blackfish._]
For the preparation of the finest oils, known as "Virgin oil," only the pulp of olives picked by hand is used. The pulp is packed in strong linen and the oil is expressed by twisting the linen together. The pulp sometimes contains as high as 70 per cent of oil.
Its last traces of adhering acid are removed by rigorous and repeated shaking with one hundredth part of their weight of caustic soda lye. After the mixture has stood for several days a large quantity of water is added and the oil floating on the top is poured off.
Though the oil is now free from acid, it still contains coloring matter and other substances which would prove injurious. It is then mixed with very strong alcohol, ten parts of the former to two of the latter, and thoroughly mixed by shaking. The bottle containing the mixture is then placed in the sun and the mixture shaken several times a day. In the course of two or three weeks the oil will have become white as water, when it is withdrawn from the alcohol, on the surface of which it floats. The purified oil is placed in small bottles, tightly corked, and kept in a dark, cool place. (68.)
[Illustration: _Fig. 3.--Relative Size of a Blackfish and Man._]
[Illustration: _Fig. 4.--D. C. Stull's Watch Oil Factory, Provincetown, Mass._]