Ferreiro - Measure of the Earth: the enlightenment expedition that reshaped our world

Table of Contents

In Measure of the Earth, Larrie Ferreiro tells the dramatic story of the first international scientific expedition to South America to establish the precise dimensions of the globe. The French scientists who led the expedition to the Andes overcame incredible adversities traversing the jungles and highlands of equatorial Peru, surviving near mutiny, attacks by local inhabitants, war, siege, and the skepticism of fellow academicians in their homeland to complete their mission and achieve lasting fame. Beautifully written, Ferreiros book provides an authoritative and gripping account of one of the greatest scientific breakthroughs of the Enlightenment.

James Horn, author of A Kingdom Strange and A Land as God Made It

Ferreiros Measure of the Earth nicely captures the scientific complexity and physical difficulty of this extraordinary expedition. At the same time, the author provides richly textured portraits of all the principal protagonists, whose personal foibles and rivalries sometimes undercut their professional skills. This is a compelling tale of international politics, Enlightened science, and human drama, played out on both sides of the Atlantic.

Carla Rahn Phillips, University of Minnesota, Twin Cities

TO MY WIFE, MIRNA,
AND OUR SONS, MARCEL AND GABRIEL:
THIS BOOK IS ABOUT THE PAST,
BUT THEY ARE THE PRESENT AND THE FUTURE.

Members of the Geodesic Mission

Political Figures

Others

Colonial South America, circa 1740. Illustration: Eliecer Vilchez Ortega.

Audiencia of Quito, circa 1740. Illustration: Eliecer Vilchez Ortega.

Each day at first light, long before the sun peered over the eastern ridge of the Andes, the two scientists were at work in the open fields, adjusting the wedges and planks under their measuring poles to keep them level. The three wooden poles, each twenty feet long and painted a different color, with paddle-like copper plates capping both ends, were arrayed end to end along the ground. They followed the survey baseline that had been scraped out of the landscape several weeks before: a dusty brown ribbon of bare earth, arrow-straight and barely as wide as a forearm, running from one horizon to the other. A thin cotton cord, pulled taut between two stakes and checked for level by three assistants, guided the men as they picked up each pole and moved it forward. They carefully placed the forward pole so that it barely touched the one behind it, ensuring that its exact position would not be disturbed by the movement. More wedges were placed to level the poles, and then each man meticulously penned the measurement in his little notebook. They continually made corrections for the length of the poles as they expanded in the rising equatorial heat, comparing them with a precisely calibrated six-foot iron rod called a toise, which they kept cool in the shade to prevent it, too, from expanding. During the month of October 1736, they repeated these steps thousands of times, working with some haste to survey the baseline from north to south before the rains began.

Pierre Bouguer, the senior of the two scientists and, at age thirty-eight, the oldest member of the group, labored under the unaccustomed physical effort. At almost two miles of altitude, his energy was quickly sapped by the thin atmosphere, which offered little oxygen and even less protection against the sun. It would hardly have seemed fair; only a few miles to the south was a seemingly perpetual cloud cover, which obscured the mountains and cooled the hilly green lands underneath.

The scientists had chosen the plateau at Yaruqu, about twelve miles east of Quito, the provincial capital of northern Peru, to lay out the baseline for their measurements because it was relatively flat and had clear views to the peaks around them. But the plateau was lower than the surrounding hills, and they soon found that it had its own microclimate, further hampering their task; though cool at night, it became very hot during the day and was exposed to high winds that sometimes generated towering whirlwinds of sand and dust, one of which had recently killed a local Indian.

This dichotomy between expectations and reality was already becoming a hallmark of their mission. Plans that seemed to be ideal on first inspection were plagued with overwhelming problems when actually executed. These problems went far beyond the normal, expected setbacks of any scientific expedition. It was almost as if the Earth itself was refusing to reveal its true measure.

Yet it was the measure of the Earth that they had journeyed thousands of miles to seek. Bouguer was one of three members of the French Academy of Sciences who, with the agreement and protection of the king of Spain, had been sent to the Spanish Viceroyalty of Peru in order to carry out precise measurements of the Earth. Traveling with several aides and two doctors, and accompanied by two young Spanish navy officers, the scientists had arrived in Quito in May 1736 after two years of planning and a years voyage from Europe. Their orders were to determine the length of a degree of latitude at the equator, a measurement that could be compared with a degree of latitude that had already been established in France. By this comparison, the shape and measure of the Earth would be known with certainty for the first time.