The 'Cavendish Experiment' can be used to determine the gravitational constant of the earth (G) using an apparatus (torsion balance) designed by geologist John Mitchell (1724-1793). It was first used and improved by Henry Cavendish (1731-1810) who, in 1798, used the results to calculate the average density of the earth. This allowed calculation of earth's mass ("weighing the earth") and G.

Other Links:
- The Mitchell-Cavendish Experiment by Laurent Hodges, Iowa State University.
- Measuring the Mass of the Earth by Donald G. York, Univ. Chicago; contains experimental setup and calculations. (requires Adobe Acrobat)