This beautiful illustration celebrates an 1821 experiment at Madras Observatory to determine the exact length of a seconds-beating pendulum(1).
Comparison with data from England enabled the elliptical figure of the earth to be calculated. Astronomer John Goldingham peers through a telescope at the Kater’s pendulum; the second Assistant, Thiruvenkatachari, reads the clock; and the first Assistant, Shrinivasachari, notes down the readings.