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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                                <s>[?]</s> of pendulums showed that the fault was not in
the agate planes but in the knife-edges. Mr. Simms
on examination found that when the attaching screws were
relaxed, the bearing <s>[?]</s> on the agate planes was
continuous and perfect. It was evident therefore
that the fault was in the surface of the brass blocks. On filing these
it was found easy to load the knife-edge into any
form. A surface was at length given to the brass
which made the bearing of the knife-edges upon the
agates absolutely perfect, as far as the eye could
discover.
(insert from page 22) The upper and  lower pendulum when mounted in their proper stations, vibrated in parallel planes, as nearly as possible in the direction of magnetic East and West.
17. In fitting up the comparison-clocks, a small
alteration was made which proved exceedingly
convenient. The illuminated disk (to be concealed
by the tail of the invariable pendulum) was an
inclined section of a small cylindrical block attached
by a central screw to the <s>[?]</s> bob of the clock pendulum.
The inclined surface was covered with gold-leaf. A hole
(covered with glass) <s>were</s> was made in <s>the</s> each side<s>s</s> of the
clock case, and through <s>one</s> either of these the light of the

                            
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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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