Account of pendulum experiments undertaken in the Harton Colliery for the purpose of determining the mean density of the Earth

Abstract

In the first section of this paper, the author explains the reasons, founded on calculation, which appeared to make it probable that the comparison of gravity at the top and the bottom of a mine would give means of determining the earth’s mean density with accuracy, perhaps superior to that obtained in the Schehallien or the Cavendish experiment; and which induced him first in the summer of 1826 (in concert with Dr. Whewell), and again in 1828 (with Dr. Whewell, Mr. Sheepshanks and others), to try the experiment in the Dolcoath mine near Camborne in Cornwall. These attempts were both frustrated by accidents having no connexion with the essential parts of the experiment. After a lapse of many years, he found that several circumstances (of which one was the general familiarity with the manipulation of the galvanic telegraph and the facility of applying it to the comparison of widely separated clocks) were very favourable to a repetition of the experiment; and having selected the Harton Colliery in the neighbourhood of South Shields as a fit place, in which two stations could be found in exactly the same vertical hut at 1256 feet difference of height, and being assured of every assistance from the owners of the mine, he proceeded with the experiments in the months of September and October 1854.