The ordinary means of reducing friction is to apply oil, or some other unctuous substance, to the parts which move upon each other. Some disadvantages attend this expedient, but till a better is suggested they have to be endured. The cost of the oil expended in maintaining in proper condition the axles of the machinery in a foundery, or of the rolling stock of a railroad, amounts to a large sum annually; while the want of neatness which its use makes, to a certain extent, inevitable, and the labor which must be constantly employed to prevent this want of neatness from becoming much greater than it is, are serious items to be set off against its positive usefulness.
The object of Mr. Girard is to get rid of all these drawbacks by the simple expedient of substituting water for oil. It would not avail to apply water precisely as oil is applied. Though any one's experience may tell him that two smooth pieces of metal will slide more smoothly on each other when they are wet than when they are dry, yet every one knows also that oil facilitates the movement much more perceptibly than water; and also, that in the case of oil there is no difficulty in maintaining the lubricating film, whereas water easily evaporates, and in case of the accident of even a moderate elevation of temperature, it would be expelled from the joint entirely. Mr. Girard proposes, therefore, to employ the water to act, first, by its pressure, to lift the Journal to be lubricated; and secondly, by its fluidity, to form a liquid bed or cushion between the journal and its box, on which the journal may rest in its revolution, without touching the metal of the box at all.
The construction will be understood by referring to the figure. One of the journals is represented as removed, and in the cylindrical surface of the socket are seen grooves occupying a considerable part of the area exposed. These grooves communicate, by an aperture in the middle, with a tube which is represented externally, and which sends a branch to the other journal, through which water under a heavy pressure is introduced into the box beneath the journal. The effect of the hydraulic pressure is to lift the axle, opening a passage for the escape of the compressed water, which at the same time, because of its release from compression, loses the power to sustain the weight. If, therefore, by the first impulse, the axle is thrown upward to any sensible distance, it will immediately fall back again, once more confining more or less completely the water. After one or two oscillations, therefore, the axle will settle itself at length in a position in which, while the water will escape, it will escape but as a film of inappreciable thickness. In this condition the journal turns upon a liquid bed, and the resistance to its revolution is so excessively small that a slow rotation given by hand to a wheel sustained by it will be maintained for many minutes without perceptible retardation. In fact, the most striking illustration which can be given of the immense superiority of the palier glissant over a support lubricated in in any other way, is furnished by placing two precisely similar wheels or disks side by side, weighing five or six pounds each, with a diameter of seven or eight inches, and journals of half an inch in diameter; one of them furnished with paliers glissants, and the other with boxes lubricated with fine oil. Give each of them a velocity of rotation of about one revolution in a second; the one lubricated with oil will come to rest before the other begins to give evidence of any sensible retardation; but if at any moment the stop-cock which supplies the water to the second be turned, this one will also stop, and its stopping will be instantaneous.
It might be supposed that a journal supported in the manner above described would be unsteady and liable to injurious vibrations. This is not the case, and it is easy to see why not. When the journal is truly in the middle of the socket, that is to say when there is an equal distance between it and the wall of the socket on either side, it will be equally pressed from both sides. But if it is in the least displaced laterally, the pressure on the side toward which it moves will instantly increase, while that on the other side will correspondingly diminish: both causes transpiring to resist the displacement, and to maintain the journal in the position of true equilibrium.
The water pressure by which these "slippery supports" are supplied must be created by a force pump worked by the machine itself. The reservoir need not be large as the expenditure of water is very minute in volume. To the objection which may naturally be made, that the working of the pump must be a tax on the motive power without return, a reply at once simple and satisfactory is found in the experience of Mr. Girard, that the working of the pump does not consume so much as half, and sometimes not more than one one quarter, of the power which is lost in friction when the ordinary modes of lubrication are employed; so that by the adoption of this expedient the available power of the machine is very sensibly increased after deducting all that is expended in the performance of this additional work.
BEES BENEFICIAL TO FRUIT.--Dr. A. Packard, editor of the American Naturalist, replies to a query in regard to the effects produced upon fruit by the agency of honey bees, that all the evidence given by botanists and zoologists who have specially studied the subject, shows that bees improve the quality and tend to increase the quantity of fruit. They aid in the fertilization of flowers, thus preventing the occurrence of sterile flowers, and, by more thoroughly fertilizing flowers already perfect, render the production of sound and well developed fruit more sure. Many botanists think if it were not for bees, and other insects, many plants would not bear fruit at all.
Steamboats on the American plan are to be introduced on Lake Geneva, Switzerland. This will add very greatly to the comfort and pleasure of tourists on that beautiful lake.