The Schiehallion experiment
Schiehallion viewed across the River Tummel
Schiehallion's isolated position and regular shape led it to be selected by Charles Mason for a ground-breaking experiment to estimate the mass of the Earth in 1774. The deflection of a pendulum by the mass of the mountain provided an estimate of the mean density of the Earth, from which its mass and a value for Newton's Gravitational constant G could be deduced. Mason turned down a commission to carry out the work and it was instead coordinated by Astronomer Royal, Nevil Maskelyne. He was assisted in the task by mathematician Charles Hutton, who devised a graphical system to represent large volumes of surveyed heights, later known as contour lines.