One of the most stupendous tasks in the history of science, started 220 years ago by William Lambton and completed four decades later by George Everest, resulted in the Great Indian Arc of the Meridian. It also established that the Himalayas constituted a mountain range and Mount Everest was the highest point on the earth. Two hundred years ago, on April 10, 1802, the British surveyor Col. William Lambton began an ambitious, audacious and mathematically meticulous scientific odyssey at St. Thomas Mount in Madras (now Chennai). It took four decades to be completed. The project ended on the foothills of the Himalayas. Lambton carefully laid the baseline, which stretched across a distance of 12 kilometres between St. Thomas Mount and another hillock in the southern direction, for the "measurement of the length of a degree of latitude" along a longitude in the middle of peninsular India.