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Knight's Mechanical Encyclopedia (ed. Knight) 8 4 Browse Search
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Knight's Mechanical Encyclopedia (ed. Knight), D. (search)
ng-frame for the diamondpoint being attached to some fixed part of the framing of the machine. Donkin followed up the matter in 1823 in devising correctional methods for Maudslay's devices, to which we cannot devote room. See Holtzapffel, pp. 651 – 655. In 1843, Mr. Sims applied self-acting apparatus to Troughton's circular dividing-engine, and an instrument of their manufacture may be seen at the Coast Survey building, Capitol Hill, Washington. It has been somewhat modified by Mr. Wurdemann, of Washington, and is now driven by a small turbine in the stand. See graduating-machine. Di-vid′ing-sink′er. （Knitting-machine.) One of the pieces interposed between jack-sinkers, which, being advanced while the latter are retracted, force the varn between the needles of each pair, so that by the joint action of the jack-sinkers and the dividing-sinkers the yarn is looped on each of the needles. Div′ing-bell. An apparatus, having some analogy in shape to a bell, in w
Knight's Mechanical Encyclopedia (ed. Knight), L. (search)
to a radius of 1,000 feet will have its second (1″) graduations 0.058733 + of an inch apart, nearly 6/100 of an inch. The level-trier constructed and used by Mr. Wurdemann (the eminent optical and surveying instrument maker, of Washington, D. C., to whom I am indebted for the present detailed information) has second (″) graduatioure upon any one part of the tube than on any other throwing the tube out of true, so that given lengths of different arts of the tube have a different value. Mr. Wurdemann, on the contrary, suspends the tube as independently as possible, putting a band of paper around each end of the tube and clamping it in its brass holder by nuired portion of the air may be imprisoned in the chamber, to adapt the instrument to work in an atmosphere of any temperature, with a bubble of a normal size. Mr. Wurdemann was the first to hermetically seal a tube containing the chamber, previous to which time it was closed by glass plates, bladder, and glue. The most curiou
Knight's Mechanical Encyclopedia (ed. Knight), P. (search)
n pointed to the same objects in turn from the new station, and the lines of direction marked on another sheet of paper. The two triangulations being placed on a plotting-table at the proper distance between stations, on the required scale, the lines of direction from each station are prolonged, and their intersections give the angles, as in figure b, which is supposed to be a fort whose angles are all distinguishable objects, and whose sides are straight lines between the said angles. Wurdemann's plane-table is a geodetical instrument consisting of two main parts: (1.) The motion works on a tripod, including leveling-screws and a horizontal movement, with clamp and tangent, above which is fastened down the drawing-board, which receives the paper. (2.) On this is placed the alidade, consisting of a broad metallic ruler with level, an upright column, near the middle, carrying above a telescope on a horizontal axis, so as to have a vertical movement of about 30° each way from the ho
Knight's Mechanical Encyclopedia (ed. Knight), T. (search)
he main limb of the instrument is fastened. The central column is of cast-iron, and the principal vertical axis of steel plays within the column. The upper or large end of the axis has attached to it a plate carrying, firstly, three reading micrometer microscopes, 120° apart; secondly, two columns with Y's for receiving the pivots of the telescope axis. The pivots rest with one half of the diameter in the Y's, the other half projecting for the legs of the striding level to rest upon. Wurdemann's theodolite. The telescope is 38 inches focal length, the object-glass 2 9/10 inches aperture, provided with a 4-inch vertical finder-circle for use in taking solar or star azimuths, and on the right-hand side of the telescope is the usual clamp and tangent for vertical fixture and movement. A small central reflector of 1/10 inch diameter throws the light from a lamp attached outside to the cross lines of the eye-piece. The light from the lamp, passing through the telescope axis to