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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                                Log Rate Pendulum 1821/Rate Pendulum 8 = 0.00072568.

This agrees so nearly with the result of Comparison A as
greatly to increase the presumption that some change took
place in one pendulum after the Seventh Series.

75. Let then z be the increase ( in units of the 8<sup>th</sup>.
decimal of the logarithm) which ought to be made for
every degree of temperature. Taking the difference between
the two first lines of Comparison A,
     554 = z x 75.19
     whence z = 7.37 nearly
              = 1/28 of the correction employed in our tables.

As the mean excess of temperature at the lower station
in the Harton Experiment was 7<sup>o</sup>.13, the correction to
be added to the rate below is 53, or the correction to the
gravity is 106. Therefore (see article 45), Log Gravity below/Gravity above
= 0.00002358, or Gravity below/Gravity above = 1.00005429
Using this number in the equation of article 60,
    0.00006603 = 0.00017984 x d/D

whence D/d = 2.7236.
And the Earth's mean density (article 62) will result
6.809.
                            
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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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