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REPAIRING CRACKED IRON PULLEYS. This is done by local heating. The crack in the rim is opened by means of an screw acting on the two adjoining spoke-, -:) .'s to make a gap about 1-16in. to 1-24in. in width. Welding- metal being then melted in the cn'ck by means of the oxy-acetylene name, the ex- pansion-screw is withdrawn quickly, while the metal is still red-hot, and the elastic re of the rim counteracts the contraction of the joint in cooling. No special care is needed in cooling, and the metal can be tempered with out risk of cracking. ,-+-- LOCKING SCREWS IN PLACE. I submit the following as a great help to usera of air motors, and more particularly to those machinists having to make iin. screws in a loin. or 18in. engine-lathe with nothing but ordinary hand-dies. We all have our troubles to keep screws in the lower cover of our air motors. To overcome it, leave the heads §in. long, and drill a 5-22in. hole close to the shoulder. Then put your slot for the screw-driver in to the usual depth. After the screws are in place, run a. small steel wire through the holes, and, when through all of them, fasten the two ends to- gether. It is obvious your screws will not turn far. We have had our motors come in with but one screw in. the cover, and the balls everywhere except in the ball-race.—"Machinist' in the "American Machinist." --+-- A SUPPOSED NEW MINERAL. A specimen of a mineral, forming portion of a, mass stated to have been found in the basalt of County Antrim, was recently sent for ideutinca- tion to the omce of the Geological Survey of Ire- land by Mr. S.B.Wilkinson, the senior geolo- gist, to whom it was handed by the finder. As it presents some peculiar features, and appears to be new to science, we take this opportunity of recording its occurrence. The complete exami- nation of the mineral will necessarily occupy some time. The mineral strongly resembles cobaltite in appearance. Its lustre is metallic, hardness about six. It breaks with a. surface which, under the microscope, shows a finely con- choidal structure. When etched with an acid a crystalline structure becomes apparent; it is fusible with difficulty. but in the oxyhydrogen flame it melts without apparent alteration. Heated in a closed tube, it does not yield any sublimate. When the mineral is powdered, or sven its surface scratched, it emits an odour like that of acetylene prepared from commercial calcium carbide. Hydrofluoric acid dissolves the mineral, the other acids have little effect upon i't. while it is readily composed by fusion with the alkaline hydroxides. A preliminary chemical analysis shows that the mineral is essentially a compound of iron, silicon, and carbon.—Richard J. Moss and Henry J. Seymour, in Nature." --+-- LUBRICATION OF A CUTTING TOOL. It has always been a puzzle to me (writes Mr. W. H. Booth, in the American Machinist'") how lubricant could find its way to the point of a cutting tool. I can only account for it by two things—first, capillarity, and, second, by dis- believing that much cutting is done by the edge of the tool. It seems probable, if we will mentally ensconce ourselves at the cutting edge, that the metal cut is wedged open by the two faces of the tool which nm: in the edge, and that the opening is so far in advance of the edge that there is time for r'ome lubricant to find its way to the edge. The advance of the metallic division ahead of the edge cannot be great, or a dullpd edge would not be so much less emeient than. a sharp edge. once a cut has started. That it is less emeient seems to prove that there is something in a keen edge. Thus we do not seem to get much nearer to a solution of the lubrication problem. Some years ago a rather interesting question in lubrication presented itself. A set of pumps, driven by a worm and wheel, were required to be tested for general sunicipncy. The worm was below the wheel, and there was a thrust bearing in a narrow cylindrical recess out of the oil- casing which enclosed the worm and wheel. A thick oil was filled into the casing, and the test was made. The thrust bearing soon grew un- bearably hot, and it looked much as though the pump would be condemned. Quite suddenly the box went comparatively cool, and no further heating took place. The cooling coincided with the thinning or liquefying of the oil. At first this was so very thick that it could not freely enter the thrust-chamber against the tendency of the worm to draw the oil away from the thrust recess and pile it up to the opposite side of the casing. But this piling up ceased when the oil became hot and thin, for it could then get well into the thrust collars, and these cooled at once, and the test was declared good. Now, here was a case where the contractor benefited by a long test which simply proved that the cont.ractor-'s estimate of the thickness of oil re- quired was incorrect. A thinner, oil would have run cool from the start, in all likelihood, and this is confirmed by the experience of many— that a thin oil is a better lubricant than a thick oil up to the point where the pressure begins to squeeze the oil from between the surfaces. Presumably this explains the benefit of long bearings, for they admit of the use of thinner oil without squeezing it out from between tha lubricated surfaces. --+-- "WET MOON nAND" DRY MOON." Popular superstition dies hard. No one who expends any thought on the matter can possibly connect rainfall with the direction of the moon's cusps; yet many persons still believe that on tf.e position of the lunar crescent depend changes in the weather which may be foretold with accuracy. The reasons for the alteration in the appearance of the new moon. at diSerent times. together with some interesting variants of the superstition, are given by Mr. Arthur K. Bart- lett. He writes: At the time of new moon, the cusps or horns> of the crescent sometimes lie in a line which is nearly perpendicular with the horizon, and at other times in a line nearly parallel with the horizon. In the former case the moon is commonly described as wet moon. and in the latter case as a "dry" moon, and owing to the changing position of the crescent seen on the western sky after sunset, such expres- sions as these are frequently heard: If the moon lies so water can not run out, we shall have a drought'; < A wet moon is one upon which the Indian can hang his powder-horn,' etc. Now. it is a fact not generally known that the crescent moon always appears upon its back" in spring, near the vernal equinox, and upon its end in autumn, near the autumnal equinox, and Lie,,e positions, which occur regularly each year, may be easily understood by a little consideration after the conditions have once been carefully explained. This change of direction the moon's < horns' are turned is caused by the varying position of the moon, when at her new" re!a- tively to the sun and the earth, and depends upon the difference in declination of the sun and moon. If the moon be further north than t'he sun after the 'new,' the sunlight strikes under her and she appears with her' horns' upturned; but if she be further south the light reaches around her disc to the northward, and her 'h,oriis appear nearly vertical, as if the cres- cent moon was resting upon one of them. \Ve see the moon in varying positions on the sky. and at first sight there appears to be no definite relation between her position and the position of her cusps or < horns: In fact, this feature of her aspect has seemed so changeful and capricious that it has even been regarded as a weather token. But in reality there is a simple relation always fulfilled by the moon's horns.' or points of the crescent. The line joining them is always at right angles or perpendicular to a line drawn from the sun to the moon, so that the 'horns' are always turned directly aw.;y from the sun. The exact position in which they will stand at any time is. therefore, easily pre- dictable, and has nothing whatever to do with the w.eather." t


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