How did John Michell contribute to the Cavendish experiment?

John Michell was instrumental to the success of the experiment famously conducted by Henry Cavendish. Michell, a British geologist and astronomer, independently conceived the principle of the torsion balance and designed the specific apparatus used to measure the gravitational attraction between lead spheres.123

Although Michell died in 1793 before he could complete his work, he had intended to use this instrument to determine the mean density of the Earth. Cavendish subsequently acquired Michell's apparatus and followed the method prescribed by him to perform the experiment in 1797–98. While Cavendish modified the setup—notably by placing it in a sealed room to eliminate environmental disturbances like air temperature fluctuations—the core design and experimental foundation were provided by Michell. Through this collaboration of design and execution, the experiment successfully measured the Earth's density and provided the data later used to calculate the gravitational constant, G.123