Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy
20<sup>+</sup> Plate [ ] contains <s>a</s> views of the pendulum- apparatus nearly in the state in which it was used in the Upper Station. The principal diagram is a front view of the apparatus as mounted at Greenwich, taken with the camera lucida; and may be trusted for general accuracy. The iron bars of the pendulum-stand are about 1 1/4 inch square. The stand of the clock does not touch the pendulum stand in any point. The hexagonal frame introduced into the box-frame is conspicuous in this view. The battery is not the same which was used at the <s>[?]</s> mine. The mounting at the lower station was exactly similar, mounting only the journeyman-clock and the battery. The frame with agate-planes (represented on a larger scale), which is planted on the top of the box-frame, is supported on three screw- feet; the screw-stalks are perforated, <s>[?]</s> two are cut with an internal screw-thread, and long screws are passed upwards through smooth holes in the box-frame, and act in those internal screw-threads and draw them firmly down; the perforation in the third is smooth, and the long screw which passes down through it acts in a screw-thread cut in the box-frame. At the sides of the blocks which carry the agate-planes are notched brass plates turning upon pins, connected by a stouter piece of brass beyond the pins, through which a screw passes that acts in the solid block below; by driving this screw, the notches are raised, and engage with the ends of the pendulum-knife-edge, and lift it off the agates.
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Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy, 1855. From The Royal Society, PT/54/5
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