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

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