Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy

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                                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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Manuscript details

Author
George Biddell Airy
Reference
PT/54/5
Series
PT
Date
1855
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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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