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 Mining Instruments A simple tapering pointer fits the disc, running from the centre to the edge, and then extends to a universal pivot for an eye to attach a line. An alternative attachment incorporates a pointer, a plumb-line and a vertical semicircle: a pillar rises from the centre, with an index at its base, and three arms extending from supports on the pillar, the outer two carrying a vertical arc of 120 degrees, the central one an index moving over this arc with a hook at the end for a line. The arc has a scale between the vertical points, 12 to 0 to 12, divided to 1, subdivided to 1/2 and to 1/4, numbered by 1. At the top of the pillar is a finial and a suspension for a plumb-line hanging between two rings and extending to a target, all supported from the pillar. There is a smaller horizontal disc, with divisions similar to the larger one, and the cardinal directions similarly marked, with an index arm. There is a disc with a centrally pivoted arm for calculating or plotting, with circular scales divided similarly to the other two. There is a brass lantern, probably for a candle, with a pivoted attachment for a line, and a smaller lantern. There is a triangular plumb-line frame with hooks on the base of the triangle, for suspending from a line, and a turned brass bob for a plumb-line. A fitted case is covered with brown leather, with decorative gold tooling; the interior is lined with chamois leather. Jim Bennett |