Sizing Up the Planet

Measure of the Earth: The Enlightenment Expedition That Reshaped Our World
By Larrie D. Ferreiro
Basic Book, 2011, 353 pages

In Review


Who would have thought that a book about an obscure eighteenth-century surveying expedition could be a good read? Not I, frankly. But I’m pleased for once to admit error. Measure of the Earth rescues its subject from the margins of history as it explores intriguing events and individuals, and bizarre locales and cultures.

The shape of Earth prompted a fierce intellectual debate in Europe in the first decades of the eighteenth century. Acolytes of René Descartes maintained that the French philosopher “implied that the Earth was elongated at the poles like an egg,” Larrie D. Ferreiro writes in his new book. The great British mathematician Isaac Newton argued something else, suggesting “that the Earth’s spin caused it to bulge at the equator and flatten at the poles.” French scientists of that era concluded that if a degree of latitude measured at the equator correlated with a degree of latitude measured in France, it would be possible to discover who was correct, Descartes or Newton.

The controversy wasn’t restricted to scholars. The French government, which regarded science as inseparable from realpolitik, realized that the resolution of the issue would greatly assist navigation, and hence buttress the military and economic fortunes of any nation that possessed the solution to the mystery. And so France organized an expedition to establish the measurement of an equatorial degree of latitude. The French enlisted the cooperation of their then-ally Spain, because the most accessible equatorial territory lay in Spain’s South American colonies. The Geodesic Mission to the Equator (ten Frenchmen, two Spanish naval officers) arrived in what is now Ecuador in 1736.

The mission’s responsibilities – surveying terrain and recording astronomical phenomena – were expected to be carried out expeditiously. It didn’t turn out that way. The team’s nominal leader, Louis Godin, was a pompous, corrupt, petty tyrant who was detested by most of his colleagues and whose misbehavior seriously hobbled the expedition’s professional activities. (Bosses, unlike science, never seem to evolve.) Landscape, weather, and complex scientific instruments were invariably problematic. Disease afflicted the mission; one participant died of malaria. A mob murdered a team member and wounded Pierre Bouguer, who was the unsung hero of the mission. When Bouguer finally returned to France (he was the first of his associates to do so), it was nine years after the expedition had embarked from Europe. Bouguer delivered to the authorities proof that Newton’s theories were accurate. As it happened, those theories had already been confirmed before Bouguer’s homecoming.

But the mission was significant nevertheless. South America was terra incognita outside of Spain, and the books and reports of the expedition’s French members introduced the region’s plants and geography to an information-hungry Europe. The Geodesic Mission also inspired future explorations of South America, particularly the journey of the great German naturalist Alexander von Humboldt. Moreover, Ferreiro writes, “[t]he expedition’s real impact was the way it reshaped our world, in ways its founders could never have imagined. The Geodesic Mission inaugurated a spate of large-scale international scientific expeditions that rewrote our understanding of the planet, and it gave us the concept of South America as a unique place, separate from its mother country of Spain, which would eventually give birth to the new nations of Latin America.”

While Ferreiro makes the scientific goals of the expedition clear, I must confess that I found many of the book’s descriptions of surveying and astronomical-observation techniques difficult to comprehend. Fortunately, Measure of the Earth contains much of interest even for those whose grasp of math is shaky. The author is a proficient storyteller and an assiduous researcher, and this book was clearly a labor of love. Ferreiro, I think, will persuade readers of the lasting stature of some very resourceful, stalwart men.

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