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The anti-frictional properties of these oils under the condition of these experiments are expressed in the following order :

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It is no disparagement to the qualities of an oil that it is low in the foregoing list, except so far as it relates to the resistance of friction under these conditions. For circumstances of great pressure and slow motion, I am of the opinion that the order of the list would be varied; and if the question of endurance were only to be considered, still another change in the order would be necessary.

A portion of a lot of unbleached sperm oil (sample 17) was bleached expressly for these tests (sample 18) but the results of the two are so nearly uniform as to be practically identical. The result of bleaching does not affect the anti-frictional properties of the oil, although it undoubtedly reduces its gumming qualities.

The friction of sperm oil is subject to sudden variations which occur at certain temperatures for the same sample of oil. The explanation of this lies in the fact that sperm oil consists of a large number of varieties of spermaceti, each of which is liquefied at certain temperatures, at which the oil is relieved of waxy or at least gelatinous particles and becomes a more perfect lubricant.

This is very apparent in the irregularities existing in the graphical representations of the tests of samples marked B and C.

The friction of lard oil for high temperatures exceeds that of any other lubricant in the list; and this adhesive quality enables it to remain on tools used for cutting iron.

In conclusion, it may be stated that the data necessary to determine the safety and efficiency of a lubricant comprise :

1. The flashing point of its vapor, which is ascertained by slowly heating a sample over an oil bath, quickly passing a small flame over the oil and noting the temperature at which the vapor first flashes. The danger from an oil does not arise from the point at which the oil actually ignites, but at the lower temperature when the inflammable vapor bursts into flames which communicate fire to a distance limited only by the extent of the vapor.

2. The quantity of such volatile matter is important both as respects safety and value. The heat of friction liberates that portion of the oil which is volatile at the temperature of the bearings; filling the mill with a dangerous, noxious vapor, and also dissipates in the air a portion of the oil which is paid for by the gallon, but does not serve to give any return of value in lubrication.

The quantity of matter volatile under 140° Fah. is measured by heating a known weight of oil in a watch glass and maintaining a constant temperature of 140° Fah. for twelve hours. This simulates the conditions of the temperature of the bearings mentioned previously, and the maximum time that it would be consecutively heated:

In the case of mineral oils the loss from evaporation varied from less than one up to thirty per cent. With animal and vegetable oils there is a slight gain in weight due to oxidation.

3. The tendency to spontaneous combustion is estimated by a uniform amount of cotton waste smeared with a certain quantity of oil.

A thermometer whose bulb extends to the centre of the mass indicates any rise of temperature due to oxidation. Any gain of weight during the preceding evaporation test shows a liability to spontaneous ignition.

4. Freedom from acid is an important factor in oil, because acid is a cause of corrosion of metals, and will tend to remove the oil from the frictional surfaces where adhesion is indispensable. The presence of acids is shown by corrosion of copper.

5. The anti-frictional properties of an oil can be measured only by direct trial under the desired conditions of pressure, velocity and temperature.

The results of these experiments show that a lubricant must have a certain adhesion to the frictional surfaces to maintain free lubrication; but beyond that point the adhesiveness of the oil resists the motion of the surfaces, increasing the friction. A thick oil

gives greater frictional resistance than a thin one; and, where ease in running is the object, the most limpid oil should be used, consistent with the conditions of the specific circumstances of the bearing.

In general terms: the specific gravity of an oil gives no indication of its value as a lubricant, in qualities of viscosity, body, or endurance.

This work is the result of a part of the ordinary service of certain mutual insurance companies. As there appears no relation between underwriting and an investigation involving questions of chemistry and mechanics, I beg to add a few words by way of explanation of the system of the factory mutual insurance companies. The better class of factories are associated together in mutually sustaining each other's losses by fire, forming the most powerful scheme of coöperation in the world. The amount of property so indemnified being some two hundred and six million dollars, or an amount exceeding three-fifths of the aggregate National Bank circulation of the United States.

The surplus of the year's work is distributed among the assured, giving the clients protection at the cost of the annual losses by fire and the expense of administering the company; the latter item amounting to a sum but little in excess of the interest accruing from the premiums deposited for indemnifying the claimants for losses.

Their policy has been to anticipate all preventable causes of fire, prescribing the ounce of prevention. Instead of charging a premium commensurate with the estimated hazard of a structure and thus betting against a chance; they demand that the mills shall be brought up to the standard of their associates in all matters of approved construction, equipment of fire apparatus and orderly supervision. Instead of making the rate conform to the risk, the risk is brought up to the rate. Mohammed does not go to the mountain, but the mountain comes to Mohammed. To achieve this end, all that theoretical knowledge can suggest, or practical experience accomplish, is utilized.

The result of this system has served to reduce the cost of indemnifying cotton mills against loss by fire, by a sum equal to saving

their capital every thirty-five years, if the saving be compounded at 6 per cent., reducing in cost every piece of New England cotton fabric.

In demanding a better class of mills as the art of their construction has been developed, in all that pertains to light, warmth, sanitation, ample stairways, protected elevators, and the abolition of garrets; in everything relating to physical comfort and safety they have incidentally accomplished more for the amelioration of the employed, than all the class legislation ever enacted in this

state.

Furthermore, the capital employed in textile manufacturing has reaped an indirect benefit from mutual insurance. Besides the reduction in rates, the decreasing number of destructive fires in such mills has also diminished the losses arising from interrupted business; a risk which is not covered by mutual insurance.

This system of mutual mill insurance was founded by the Hon. Zachariah Allen, of Providence, one of the founders of the American Association for the Advancement of Science, who is present with us to-day, his zeal for science unabated, notwithstanding the burden of over eighty-five years.

This investigation of the subject of lubrication forms a part of a study of oils, undertaken on behalf of the Mill Mutual Insurance Companies, in order to determine the conditions of safety from fire and economy in use; the chief causes of danger in textile factories being from friction or spontaneous combustion. The whole subject has been under the charge of Prof. J. M. Ordway, Professor of Industrial Chemistry in the Massachusetts Institute of Technology.

In the conduction of the lubrication tests, I desire to express my gratitude to Professor Ordway for his kindly assistance and many suggestions, rendered especially valuable by his scientific attainments and practical experience.

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