Account of pendulum experiments undertaken in the Harton Colliery, for the purpose of determining the mean density of the earth, by G. B. Airy
and I x 100/101.8 x 60.2 for pendulum 8: in which expressions the factors of I are sensibly the same. Call this proportion C. Then the number of vibrations observed is to be multiplied by <s>[?]</s> 1 + C<sup>2</sup>/64 or 1 + I<sup>2</sup> x 1/64 . (100/101 x 60.7)<sup>2</sup>. In the first instance therefore we require the logarithm of 1 + I<sup>2</sup> x 1/64 . (100/101 x 60.7)<sup>2</sup> for values of I not exceeding 2.5. The following table contains the numbers required, in units of the last figures of 8figure logarithms. I Log I Log I Log I Log I Log 0.1 2 0.6 65 1.1 218 1.6 462 2.1 796 0.2 7 0.7 88 1.2 260 1.7 522 2.2 874 0.3 17 0.8 116.1.3 305 1.8 585 2.3 955 0.4 29 0.9 146 1.4 353 1.9 652 2.4 1040 0.5 45 1.0 180 1.5 405 2.0 722 2.5 1128 Next, it is necessary to determine experimentally the law, or rather the numerical succession of values, in the diminution of the arc of vibration. For this purpose, observations were made at Greenwich on the extent of the whole arc in successive half hours. The following table contains (with sufficient approximation) the range of arc through each half hour, the middle arc
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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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