. Appleton's dictionary of machines, mechanics, engine-work, and engineering. per plate a is raised or loweredby means of a rack g, working out of tho pillar c, by means of a pinion and friction rollers, acted uponby the milled head /*. For taking an observation, place the instrument upon any linn support, with the letters Nand S asnearly north and south as maybe; but rigid accuracy in this respect IS by no means essential. Bymeans of a spirit-level and the adjusting screws <l < /, bring the plate 8 into a horiionta] position; thenraise or lower the plate a until tho suns ray is in conta
. Appleton's dictionary of machines, mechanics, engine-work, and engineering. per plate a is raised or loweredby means of a rack g, working out of tho pillar c, by means of a pinion and friction rollers, acted uponby the milled head /*. For taking an observation, place the instrument upon any linn support, with the letters Nand S asnearly north and south as maybe; but rigid accuracy in this respect IS by no means essential. Bymeans of a spirit-level and the adjusting screws <l < /, bring the plate 8 into a horiionta] position; thenraise or lower the plate a until tho suns ray is in contact with the line on which it is intended to make 452 PACKING. the observation, as at A in the diagram, fig. 2986, or until the ray appears within the double line aiat A, fio-. 2987. In either case, note the hour, minute, and second, when the ray is at A; leaving the in-strument undisturbed, the suns ray will traverse the plate in the direction of the arrow until it arrives atthe point A, when the time is again to be accurately noted. Add the results of the two observations. together, and divide by 2 ; the difference between this result and 12 hours will show the error of theclock as compared with solar time, which being corrected by the necessary equations, (of which verycomplete tables are given in the descriptive pamphlet which accompanies the instrument,) will giveeither mean or siderial time, as may be desired. OSCILLATION, CENTRE OF. The centre of oscillation is that point in a vibrating body intowhich, if the whole were concentrated and attached to the same axis of motion, it would then vibratein the same time the body does in its natural state. The centre of oscillation is situated in a right linepassing through the centre of gravity, and perpendicular to the axis of motion. OYSTER-OPENEE, Picaclts. Amongst the extensive col-lections of the products of industry, agriculture, and manufac-tures of 1849, exhibited in Paris, is a peculiar mechanical con-trivance for opening
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Keywords: ., bookcentury1800, booksubjectmechanicalengineering, bookyear1861
