This text is the graphic story of the measurement of a meridian, or longitudinal, arc extending from the tip of the Indian subcontinent to the mountains of the Himalayas. Much the longest such measurement hitherto made, it posed horrendous technical difficulties, made impossible physical demands on the survey parties and took over 50 years. But the scientific results were commensurate, including the discovery of the world's highest peaks and a new calculation of the curvature of the earth's surface.