III. On the causes of the great variation among the different measures of the Earth’s mean density

The result of the Pendulum experiments in the Harton Colliery, undertaken by the Astronomer Royal in 1854, and detailed in his paper presented to the Royal Society in January 1856, appears at first sight rather startling, as adding to the already somewhat discrepant measures or estimates of the earth’s mean density one more discordant than ever ; so that we have now values ranging from 4.7 to nearly 6.6; a range, which, in the absence of any sufficient ground for selectingany one as true to the exclusion of the rest, would seem to deprive us of all confidence in their correctness asmeasures , and leave them rather to be classed as estimates of a very rough description. But it will be my endeavour to show, that, while none of the methods employed are capable of givingstrictly accurate results, the Cavendish experiment is the one which may be relied on as giving a good approximation to the truth, within limits of error (when conducted with proper precaution) far less than those to which either of the other methods are liable.