In the early eighteenth century, European thinkers were torn between Descartes notion that the earth was spherical and Newtons contention that it was flattened at the poles. Eager to reap the great military and imperial advantages of knowing the earths exact shape, France and Spain sent an expedition of scientists and naval officers to colonial Peru to measure the degree of equatorial latitude, which could resolve the debate. But what seemed to be a straightforward survey down the Andes was quickly marred by catastrophe. In Measure of the Earth, award-winning science writer Larrie D. Ferreiro tells the full story of the Geodesic Mission for the first time, describing the remarkable scientific expedition through the eyes of the men who served on it.