[Note A: The readings of the Centigrade and Fahrenheit scales given here are not exactly equivalent; but they are near enough for all practical purposes.]
~85. Mixed Oils~ have been tried by many who have been desirous of obtaining a better lubricant. A mixture of different kinds of animal or vegetable oils--or a combination of both--has usually proved worse than any single one of the components; as, when it is known that "alterations[26] of composition occur in the animal and vegetable oils with exposure to air and light and with advancing age" (74-2), it is obvious that this chemical action is accelerated by a mixture.
The mineral oils are not subject to such alterations to any serious extent; and, when they are compounded with animal or vegetable oils, the resulting mixture partakes of the good qualities of both, according to experiments which the author has made. It would make this paper[27] too lengthy to insert the results; however, a future opportunity may not be wanting.
~86. Various Manufacturers~ of watches, chronometers and clocks, have favored the writer with more or less valuable information in answer to queries on the subject, which has been tabulated and which is shown in table XII.
It is necessary to know just what kind of oil has been used by the manufacturer of a time piece for three reasons:--
(1.) If some of the bearings need a small quantity of oil, being otherwise in such good condition--because of never having been used, in fact "new"--that it is unnecessary to take all the mechanism apart and clean it, it is very important that the operator know what kind, or variety, of lubricant has been previously used, in order not to "mix oils;" or, if a mixture is thus made, to make it intelligently. (85.)
(2.) When the oil which has been applied in the factory has not performed its functions properly in any part of a time piece, it is necessary to know what particular variety of lubricant has been used in order to substitute an oil which possesses the properties lacked by the oil previously used. (61.)
(3.) In a watch which has been so adjusted as to keep a maximum even rate, the oil is one of the factors of the variation which has been overcome. It is necessary, then, on putting the watch in order, to employ a lubricant which possesses the same variation of viscosity as the oil which was used during adjustment. (84.)