The Great Indian Arc of the Meridian, begun in 1800, was the longest measurement of the earth's surface ever to have been attempted. Its 1600 miles of inch perfect survey took nearly fifty years, cost more lives than most contemporary wars, and involved equations more complex than any in the pre-computer age. Hailed as 'one of the most stupendous works in the history of science', it was also one of the most perilous. Through hill and jungle, flood and fever, an intrepid band of surveyors carried the Arc from the southern tip of the Indian subcontinent up into the frozen wastes of the Himalayas. William Lambton, an endearing genius, had conceived the idea; George Everest, an impossible martinet, completed it. Both found the technical difficulties horrendous. With instruments weighing half a ton, their observations had often to be conducted from flimsy platforms ninety feet above the ground or from mountain peaks enveloped in blizzard. Malaria wiped out whole survey parties; tigers and scorpions also took their toll.