~69. Mineral Oil~ (11) has been used as a lubricant for time keeping mechanism; but as there are so many varieties on the market, each differing from the others and possessing properties peculiar to itself, and as many have made experiments which have not demonstrated that such oils possess all the essential qualities of a perfect lubricant in horology, the author believes that the abundance of kinds and qualities of mineral oils has in the past been more or less confusing to the majority of those who have experimented; and believes further, that if the proper kind and quality of such oils had been used, all that could be desired in a lubricant would have been shown to have been contained therein. Past experience has shown that many lubricants remained for years unused for special purposes to which, when tried, they were found specially adapted. Though E. Rigg was probably in error in the matter previously discussed (44) his otherwise excellent lecture contains the following:--[14] "But there is another subject that has a still closer bearing on friction as met with in time keeping instruments, and I cannot bring my lecture to a close without reference to that most fruitful source of trouble to the watchmaker--oil. Breguet, a very famous horologist, and D'Arcet, an equally celebrated chemist, worked together at this problem and what was the result? They produced an oil that was, according to their theory, perfect; but when applied to watches it proved to be worse than the ordinary oils of commerce. Since their day the chemistry of oil has not made much progress, and the methods recommended for testing oil are still very ineffectual. The only test of any use is actual trial for a long period, and under varying conditions as to temperature, nature of atmosphere, etc.; and there are several oils on the market more or less satisfying the required conditions. So far as my knowledge goes, however, all are liable to dry; and this prompts me to draw your attention to a lubricator that has come into use for heavy machinery in recent years, in the hope that it may afford a suggestion for the improvement of watch oils. I allude to the mixture of certain kinds of mineral oil with an oil that has a tendency to dry. Even a small percentage is asserted to entirely check this tendency and the resulting mixture is said to have the property of not in any way acting on or damaging the metal to which it is applied. The thickness, or 'body,' is made to vary according to the pressure to which the oil is subjected. * * * * Would it be oversanguine to hope that some such mixture, prepared from perfectly pure materials, might help even the chronometer maker to secure more uniform rates? Absolute freedom from acidity means a reduction of such electrical action as may occur at the pivots, and, therefore, a greater permanency of the oil from this point of view."